PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-25 (960789)

Clipboard (0)
None

Related Articles

1.  The Risk of Stable Partnerships: Associations between Partnership Characteristics and Unprotected Anal Intercourse among Men Who Have Sex with Men and Transgender Women Recently Diagnosed with HIV and/or STI in Lima, Peru 
PLoS ONE  2014;9(7):e102894.
Background
Partnership type is an important factor associated with unprotected anal intercourse (UAI) and subsequent risk for HIV and sexually transmitted infections (STI). We examined the association of partnership type with UAI among men who have sex with men (MSM) and male-to-female transgender women (TGW) in Lima, Peru, recently diagnosed with HIV and/or STI.
Methods
We report data from a cross-sectional analysis of MSM and TGW recently diagnosed with HIV and/or STI in Lima, Peru between 2011 and 2012. We surveyed participants regarding UAI with up to their three most recent sexual partners according to partner type. Multivariable Generalized Estimate Equating (GEE) models with Poisson distribution were used to estimate prevalence ratios (PR) for UAI according to partner type.
Results
Among 339 MSM and TGW recently diagnosed with HIV and/or STI (mean age: 30.6 years, SD 9.0), 65.5% self-identified as homosexual/gay, 16.0% as bisexual, 15.2% as male-to-female transgender, and 3.3% as heterosexual. Participants provided information on 893 recent male or TGW partners with whom they had engaged in insertive or receptive anal intercourse: 28.9% stable partners, 56.4% non-stable/non-transactional partners (i.e. casual or anonymous), and 14.7% transactional partners (i.e. transactional sex client or sex worker). Unprotected anal intercourse was reported with 41.3% of all partners. In multivariable analysis, factors associated with UAI included partnership type (non-stable/non-transactional partner APR 0.73, [95% CI 0.59–0.91], transactional partner APR 0.53 [0.36–0.78], p<0.05) and the number of previous sexual encounters with the partner (>10 encounters APR 1.43 [1.06–1.92], p<0.05).
Conclusion
UAI was more commonly reported for stable partners and in partnerships with >10 sexual encounters, suggesting UAI is more prevalent in partnerships with a greater degree of interpersonal commitment. Further research assessing partner-level factors and behavior is critical for improving HIV and/or STI prevention efforts among Peruvian MSM and TGW.
doi:10.1371/journal.pone.0102894
PMCID: PMC4100899  PMID: 25029514
2.  Human Immunodeficiency Virus (HIV) and Sexually Transmitted Infection (STI) incidence and associated risk factors among high-risk MSM and male-to-female transgender women in Lima, Peru 
Background
Men who have sex with men (MSM) and male-to-female transgender women (TW) are at increased risk of HIV and sexually transmitted infections (STIs). We evaluated factors associated with incidence of HIV, HSV-2, and chlamydia and gonorrhea (anal and pharyngeal).
Methods
We used data from the Comunidades Positivas trial with MSM/TW who have sex with men in Lima, Peru. Participants were asked about sexual risk behaviors and underwent HIV/STI testing at baseline and 9- and 18-month follow-ups. We used discrete time proportional hazards regression to calculate hazard ratios (HRs) for variables associated with incidence of each STI.
Results
Among 718 MSM/TW, HIV incidence was 3.6 cases per 100 person-years. HIV incidence was associated with having an incident STI (aHR 3.73). Unprotected receptive anal intercourse was associated with incident anal chlamydia (aHR 2.20). An increased number of sexual partners increased incident HSV-2 (aHR 3.15 for 6–14 partners and 3.97 for 15–46 partners compared to 0–2 partners). Risk of anal gonorrhea decreased with each sexually active year (aHR 0.94) and increased for unprotected compensated sex (aHR 2.36). Risk of pharyngeal gonorrhea also decreased with each year since sexual debut (aHR 0.95). Risk of anal chlamydia decreased with each sexually active year (aHR 0.96), risk increased with reports of unprotected sex work (aHR 1.61), and unprotected receptive anal sex (aHR 2.63). All aHRs have p-values < 0.05.
Conclusion
MSM/TW experience high incidence of HIV. Up-to-date prevalence and incidence information and identifying factors associated with infection can help develop a more effective combination prevention response.
doi:10.1097/QAI.0000000000000667
PMCID: PMC4501868  PMID: 25950207
HIV; HSV-2; gonorrhea; chlamydia; MSM; transgender; Peru
3.  Factors associated with previously undiagnosed human immunodeficiency virus infection in a population of men who have sex with men and male-to-female transgender women in Lima, Peru 
Medicine  2016;95(42):e5147.
Abstract
The aim of the study was to identify factors associated with undiagnosed human immunodeficiency virus (HIV) infection among men who have sex with men (MSM) and male-to-female transgender women in Lima, Peru.
We analyzed characteristics of 378 MSM and transgender women recruited from 2 sexually transmitted infection (STI) clinics in Lima, Peru. Descriptive analyses compared: (A) HIV-uninfected, (B) previously undiagnosed HIV-infected, and (C) previously diagnosed HIV-infected participants. Multivariable logistic regression models identified: (1) correlates of previously undiagnosed HIV-infection among participants thought to be HIV-uninfected (B vs A); and (2) correlates of previously undiagnosed HIV-infection among HIV-infected participants (B vs C). Subanalysis identified correlates of frequent HIV testing among participants thought to be HIV-uninfected.
Among participants, 31.0% were HIV-infected; of those, 35.0% were previously undiagnosed. Among participants thought to be HIV-uninfected (model 1), recent condomless receptive anal intercourse and last HIV test being over 1-year ago (compared to within the last 6-months) were associated with increased odds of being previously undiagnosed HIV-infected (adjusted odds ratio [aOR] = 2.43, 95% confidence interval [95%CI] = 1.10–5.36; aOR = 2.87, 95%CI = 1.10–7.53, respectively). Among HIV-infected participants (model 2), recent condomless receptive anal intercourse was again associated with previously undiagnosed HIV-infection (aOR = 2.54, 95%CI = 1.04–6.23). Achieving post-secondary education and prior syphilis infection were associated with lower odds of having previously undiagnosed HIV-infection (aOR = 0.35, 95%CI = 0.15–0.81; aOR = 0.32, 95%CI = 0.14–0.75, respectively).
Reporting semiannual testing was associated with higher educational attainment, identifying as a transgender woman, or reporting a history of syphilis (aOR = 1.94, 95%CI = 1.11–3.37; aOR = 2.40, 95%CI = 1.23–4.70; aOR = 2.76, 95%CI = 1.62–4.71, respectively). Lower odds of semiannual testing were associated with recent condomless insertive anal intercourse or reporting a moderate or high self-perceived risk of acquiring HIV (aOR = 0.56, 95%CI = 0.33–0.96; aOR = 0.32, 95%CI = 0.18–0.59 and aOR = 0.43, 95%CI = 0.21–0.86, respectively).
In our study, undiagnosed HIV-infection was associated with recent condomless receptive anal intercourse, infrequent HIV testing, lower education, and absence of prior syphilis diagnosis. Infrequent HIV testing was associated with lower education, not identifying as transgender, recent condomless insertive anal intercourse, absence of prior syphilis diagnosis, and higher self-perceived risk of HIV. Further efforts to decrease HIV transmission and increase HIV-serostatus awareness should be directed towards effectively promoting condom use and frequent HIV testing, integrated with STI management.
doi:10.1097/MD.0000000000005147
PMCID: PMC5079329  PMID: 27759645
Lima; men who have sex with men; Peru; risk factors; transgender women; undiagnosed HIV infection
4.  The Potential Impact of Pre-Exposure Prophylaxis for HIV Prevention among Men Who Have Sex with Men and Transwomen in Lima, Peru: A Mathematical Modelling Study 
PLoS Medicine  2012;9(10):e1001323.
Gabriela Gomez and colleagues developed a mathematical model of the HIV epidemic among men who have sex with men and transwomen in Lima, Peru to explore whether HIV pre-exposure prophylaxis could be a cost-effective addition to existing HIV prevention strategies.
Background
HIV pre-exposure prophylaxis (PrEP), the use of antiretroviral drugs by uninfected individuals to prevent HIV infection, has demonstrated effectiveness in preventing acquisition in a high-risk population of men who have sex with men (MSM). Consequently, there is a need to understand if and how PrEP can be used cost-effectively to prevent HIV infection in such populations.
Methods and Findings
We developed a mathematical model representing the HIV epidemic among MSM and transwomen (male-to-female transgender individuals) in Lima, Peru, as a test case. PrEP effectiveness in the model is assumed to result from the combination of a “conditional efficacy” parameter and an adherence parameter. Annual operating costs from a health provider perspective were based on the US Centers for Disease Control and Prevention interim guidelines for PrEP use. The model was used to investigate the population-level impact, cost, and cost-effectiveness of PrEP under a range of implementation scenarios. The epidemiological impact of PrEP is largely driven by programme characteristics. For a modest PrEP coverage of 5%, over 8% of infections could be averted in a programme prioritising those at higher risk and attaining the adherence levels of the Pre-Exposure Prophylaxis Initiative study. Across all scenarios, the highest estimated cost per disability-adjusted life year averted (uniform strategy for a coverage level of 20%, US$1,036–US$4,254) is below the World Health Organization recommended threshold for cost-effective interventions, while only certain optimistic scenarios (low coverage of 5% and some or high prioritisation) are likely to be cost-effective using the World Bank threshold. The impact of PrEP is reduced if those on PrEP decrease condom use, but only extreme behaviour changes among non-adherers (over 80% reduction in condom use) and a low PrEP conditional efficacy (40%) would adversely impact the epidemic. However, PrEP will not arrest HIV transmission in isolation because of its incomplete effectiveness and dependence on adherence, and because the high cost of programmes limits the coverage levels that could potentially be attained.
Conclusions
A strategic PrEP intervention could be a cost-effective addition to existing HIV prevention strategies for MSM populations. However, despite being cost-effective, a substantial expenditure would be required to generate significant reductions in incidence.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Without a vaccine, the only ways to halt the global HIV epidemic are prevention strategies that reduce transmission of the HIV virus. Up until recently, behavioral strategies such as condom use and reduction of sexual partners have been at the center of HIV prevention. In the past few years, several biological prevention measures have also been shown to be effective in reducing (though not completely preventing) HIV transmission. These include male circumcision, treatment for prevention (giving antiretroviral drugs to HIV-infected people, before they need it for their own health, to reduce their infectiousness) and pre-exposure prophylaxis (or PrEP), in which HIV-negative people use antiretroviral drugs to protect themselves from infection. One PrEP regimen (a daily pill containing two different antiretrovirals) has been shown in a clinical trial to reduce new infections by 44% in of men who have sex with men (MSM). In July 2012, the US Food and Drug Administration approved this PrEP regimen to reduce the risk of HIV infection in uninfected men and women who are at high risk of HIV infection and who may engage in sexual activity with HIV-infected partners. The approval makes it clear that PrEP needs to be used in combination with safe sex practices.
Why Was This Study Done?
Clinical trials have shown that PrEP can reduce HIV infections among participants, but they have not examined the consequences PrEP could have at the population level. Before decision-makers can decide whether to invest in PrEP programs, they need to know about the costs and benefits at the population level. Besides the price of the drug itself, the costs include HIV testing before starting PrEP, as well as regular tests thereafter. The health benefits of reducing new HIV infections are calculated in “disability-adjusted life years” (or DALYs) averted. One DALY is equal to one year of healthy life lost. Other benefits include future savings in lifelong HIV/AIDS treatment for every person whose infection is prevented by PrEP.
This study estimates the potential costs and health benefits of several hypothetical PrEP roll-out scenarios among the community of MSM in Lima, Peru. The scientists chose this community because many of the participants in the clinical trial that showed that PrEP can reduce infections came from this community, and they therefore have some knowledge on how PrEP affects HIV infection rates and behavior in this population. Because the HIV epidemic in Lima is concentrated among MSM, similar to most of Latin America and several other developed countries, the results might also be relevant for the evaluation of PrEP in other places.
What Did the Researchers Do and Find?
For their scenarios, the researchers looked at “high coverage” and “low coverage” scenarios, in which 20% and 5% of uninfected individuals use PrEP, respectively. They also divided the MSM community into those at lower risk of becoming infected and those at higher risk. The latter group consisted of transwomen at higher risk (transsexuals and transvestites with many sexual partners) and male sex workers. In a “uniform coverage” scenario, PrEP is equally distributed among all MSM. “Prioritized scenarios” cover transwomen at higher risk and sex workers preferentially. Two additional important factors for the estimated benefits are treatment adherence (i.e., whether people take the pills they have been prescribed faithfully over long periods of time even though they are not sick) and changes in risk behavior (i.e., whether the perceived protection provided by PrEP leads to more unprotected sex).
The cost estimates for PrEP included the costs of the drug itself and HIV tests prior to PrEP prescription and at three-month intervals thereafter, as well as outreach and counseling services and condom and lubricant promotion and provision.
To judge whether under the various scenarios PrEP is cost-effective, the researchers applied two commonly used but different cost-effectiveness thresholds. The World Health Organization's WHO-CHOICE initiative considers an intervention cost-effective if its cost is less than three times the gross domestic product (GDP) per capita per DALY averted. For Peru, this means an intervention should cost less than US$16,302 per DALY. The World Bank has more stringent criteria: it considers an intervention cost-effective for a middle-income country like Peru if it costs less than US$500 per DALY averted.
The researchers estimate that PrEP is cost-effective in Lima's MSM population for most scenarios by WHO-CHOICE guidelines. Only scenarios that prioritize PrEP to those most likely to become infected (i.e., transwomen at higher risk and sex workers) are cost-effective (and only barely) by the more stringent World Bank criteria. If the savings on antiretroviral drugs to treat people with HIV (those who would have become infected without PrEP) are included in the calculation, most scenarios become cost-effective, even under World Bank criteria.
The most cost-effective scenario, namely, having a modest coverage of 5%, prioritizing PrEP to transwomen at higher risk and sex workers, and assuming fairly high adherence levels among PrEP recipients, is estimated to avert about 8% of new infections among this community over ten years.
What Do these Findings Mean?
These findings suggest that under some circumstances, PrEP could be a cost-effective tool to reduce new HIV infections. However, as the researchers discuss, PrEP is expensive and only partly effective. Moreover, its effectiveness depends on two behavioral factors—adherence to a strict drug regimen and continued practicing of safe sex—both of which remain hard to predict. As a consequence, PrEP alone is not a valid strategy to prevent new HIV infections. It needs instead to be considered as one of several available tools. If and when PrEP is chosen as part of an integrated prevention strategy will depend on the specific target population, the overall funds available, and how well its cost-effectiveness compares with other prevention measures.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001323.
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
NAM/aidsmap provides basic information about HIV/AIDS, summaries of recent research findings on HIV care and treatment, and a section on PrEP
Information is available from Avert, an international AIDS charity, on many aspects of HIV/AIDS, including HIV prevention
AVAC Global Advocacy for HIV Prevention provides up-to-date information on HIV prevention, including PrEP
The US Centers for Disease Control and Prevention also has information on PrEP
The World Health Organization has a page on its WHO-CHOICE criteria for cost-effectiveness
doi:10.1371/journal.pmed.1001323
PMCID: PMC3467261  PMID: 23055836
5.  An Intervention to Reduce HIV Risk Behavior of Substance-Using Men Who Have Sex with Men: A Two-Group Randomized Trial with a Nonrandomized Third Group 
PLoS Medicine  2010;7(8):e1000329.
In a randomized trial of a behavioral intervention among substance-using men who have sex with men, aimed at reducing sexual risk behavior, Mansergh and colleagues fail to find evidence of a reduction in risk from the intervention.
Background
Substance use during sex is associated with sexual risk behavior among men who have sex with men (MSM), and MSM continue to be the group at highest risk for incident HIV in the United States. The objective of this study is to test the efficacy of a group-based, cognitive-behavioral intervention to reduce risk behavior of substance-using MSM, compared to a randomized attention-control group and a nonrandomized standard HIV-testing group.
Methods and Findings
Participants (n = 1,686) were enrolled in Chicago, Los Angeles, New York City, and San Francisco and randomized to a cognitive-behavioral intervention or attention-control comparison. The nonrandomized group received standard HIV counseling and testing. Intervention group participants received six 2-h group sessions focused on reducing substance use and sexual risk behavior. Attention-control group participants received six 2-h group sessions of videos and discussion of MSM community issues unrelated to substance use, sexual risk, and HIV/AIDS. All three groups received HIV counseling and testing at baseline. The sample reported high-risk behavior during the past 3 mo prior to their baseline visit: 67% reported unprotected anal sex, and 77% reported substance use during their most recent anal sex encounter with a nonprimary partner. The three groups significantly (p<0.05) reduced risk behavior (e.g., unprotected anal sex reduced by 32% at 12-mo follow-up), but were not different (p>0.05) from each other at 3-, 6-, and 12-mo follow-up. Outcomes for the 2-arm comparisons were not significantly different at 12-mo follow-up (e.g., unprotected anal sex, odds ratio = 1.14, confidence interval = 0.86–1.51), nor at earlier time points. Similar results were found for each outcome variable in both 2- and 3-arm comparisons.
Conclusions
These results for reducing sexual risk behavior of substance-using MSM are consistent with results of intervention trials for other populations, which collectively suggest critical challenges for the field of HIV behavioral interventions. Several mechanisms may contribute to statistically indistinguishable reductions in risk outcomes by trial group. More explicit debate is needed in the behavioral intervention field about appropriate scientific designs and methods. As HIV prevention increasingly competes for behavior-change attention alongside other “chronic” diseases and mental health issues, new approaches may better resonate with at-risk groups.
Trial Registration
ClinicalTrials.gov NCT00153361
Please see later in the article for the Editors' Summary
Editors' Summary
Background
AIDS first emerged in the early 1980s among gay men living in the US. As the disease spread around the world, it became clear that AIDS also affects heterosexual men and women. Now, three decades on, more than 30 million people are infected with HIV, the virus that causes AIDS. HIV is most often spread by having unprotected sex with an infected partner and, globally, most sexual transmission of HIV now occurs during heterosexual sex. However, 5%–10% of all new HIV infections still occur in men who have sex with men (MSM, a term that encompasses gay, bisexual, transgendered, and heterosexual men who sometimes have sex with men) and, in several high-income countries, male-to-male sexual contact remains the most important HIV transmission route. In the US, for example, more than half of the approximately 50,000 people who become infected with HIV every year do so through male-to-male sexual contact.
Why Was This Study Done?
In countries where MSM are the group at highest risk of HIV infection, any intervention that reduces HIV transmission in MSM should have a major effect on the overall HIV infection rate. Among MSM, sexual behaviors that increase the risk of HIV infection (for example, not using a condom, having anal sex, having sex with a partner of unknown HIV status, and having sex with many partners) are associated with the use of alcohol and noninjection drugs (for example, inhaled amyl nitrite or poppers) during or shortly before sexual encounters. In this study (Project MIX), the researchers investigate whether a group-based behavioral intervention reduces sexual risk behavior in substance-using MSM.
What Did the Researchers Do and Find?
The researchers recruited substance-using MSM from four US cities who had had risky sex at least once in the past 6 months. Participants were randomized to a cognitive-behavioral intervention or to an attention-control group; a third, nonrandomized group of MSM formed a standard HIV counseling and testing only group. All the groups had HIV counseling and testing at the start of the study and completed a questionnaire about their substance use and sexual risk behavior during their most recent anal sex encounter. The cognitive-behavior group then received six weekly 2-hour group sessions focused on reducing substance use and sexual risk behavior by helping the men change their thinking (cognition) and behavior regarding sexual risk taking. The attention-control group received six group sessions about general MSM issues such as relationships, excluding discussion of substance use, and sexual risk behavior. The participants in both of these groups completed the questionnaire about their substance use and sexual risk behavior again at 3, 6, and 12 months after the group sessions; the participants in the standard HIV counseling and testing group completed the questionnaire again about 5 months after completing the first questionnaire (to control for the time taken by the other two groups to complete the intervention). At baseline, about 67% of the participants reported unprotected anal sex and 77% reported substance use during their most recent anal sex encounter with a nonprimary partner. At the 3-month follow-up, the incidence of sexual risk behavior had fallen to about 43% in all three groups; the incidence of substance use during sex had fallen to about 50%. Risk taking and substance use remained at these levels in the intervention and attention-control groups at the later follow-up time points.
What Do These Findings Mean?
These findings suggest that this cognitive-behavioral intervention is no better at reducing sexual risk taking among substance-using MSM than is an unrelated video-discussion group or standard HIV counseling and testing. One explanation for this negative result might be that brief counseling is especially effective with people who are ready for a change such as MSM willing to enroll in an intervention trial of this type. Alternatively, just being in the trial might have encouraged all the participants to self-report reduced risk behavior. Thus, alternative scientific designs and methods might be needed to find behavioral interventions that can effectively reduce HIV transmission among substance-using MSM and other people at high risk of HIV infection. Importantly, however, these findings raise the question of whether more extensive, multilevel interventions or broader lifestyle and positive health approaches (rather than single-level or single-subject behavioral interventions) might be needed to reduce sexual risk behavior among substance-using MSM.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000329.
Information is available from the US Department of Health and Human Services on HIV prevention programs, research, and policy
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
HIV InSite has comprehensive information on all aspects of HIV/AIDS, including information on HIV transmission and transmission in gay men and other MSM, on substance abuse and HIV/AIDS, and on safer sex
Information is available from Avert, an international AIDS nonprofit, on all aspects of HIV/AIDS, including information on HIV, AIDS, and men who have sex with men and on drink, drugs, and sex (in English and Spanish)
The US Centers for Disease Control and Prevention also have information for the public and for professionals about HIV/AIDS among men who have sex with men (in English and Spanish)
The US National Institute on Drug Abuse has information on HIV/AIDS and drug abuse, including a resource aimed at educating teenagers about the link between drug abuse and the spread of HIV in the US (in English and Spanish)
doi:10.1371/journal.pmed.1000329
PMCID: PMC2927550  PMID: 20811491
6.  Increases in sexually transmitted infections and sexual risk behaviour without a concurrent increase in HIV incidence among men who have sex with men in San Francisco: a suggestion of HIV serosorting? 
Sexually Transmitted Infections  2006;82(6):461-466.
Background
Sexually transmitted infections (STI) and unprotected anal intercourse (UAI) have been increasing among men who have sex with men (MSM) in San Francisco. However, HIV incidence has stabilised.
Objectives
To describe recent trends in sexual risk behaviour, STI, and HIV incidence among MSM in San Francisco and to assess whether increases in HIV serosorting (that is, selective unprotected sex with partners of the same HIV status) may contribute to preventing further expansion of the epidemic.
Methods
The study applies an ecological approach and follows the principles of second generation HIV surveillance. Temporal trends in biological and behavioural measures among MSM were assessed using multiple pre‐existing data sources: STI case reporting, prevention outreach programmatic data, and voluntary HIV counselling and testing data.
Results
Reported STI cases among MSM rose from 1998 through 2004, although the rate of increase slowed between 2002 and 2004. Rectal gonorrhoea cases increased from 157 to 389 while early syphilis increased from nine to 492. UAI increased overall from 1998 to 2004 (p<0.001) in community based surveys; however, UAI with partners of unknown HIV serostatus decreased overall (p<0.001) among HIV negative MSM, and among HIV positive MSM it declined from 30.7% in 2001 to a low of 21.0% in 2004 (p<0.001). Any UAI, receptive UAI, and insertive UAI with a known HIV positive partner decreased overall from 1998 to 2004 (p<0.001) among MSM seeking anonymous HIV testing and at the STI clinic testing programme. HIV incidence using the serological testing algorithm for recent HIV seroconversion (STARHS) peaked in 1999 at 4.1% at the anonymous testing sites and 4.8% at the STI clinic voluntary testing programme, with rates levelling off through 2004.
Conclusions
HIV incidence among MSM appears to have stabilised at a plateau following several years of resurgence. Increases in the selection of sexual partners of concordant HIV serostatus may be contributing to the stabilisation of the epidemic. However, current incidence rates of STI and HIV remain high. Moreover, a strategy of risk reduction by HIV serosorting can be severely limited by imperfect knowledge of one's own and one's partners' serostatus.
doi:10.1136/sti.2006.019950
PMCID: PMC2563862  PMID: 17151031
men who have sex with men; sexual risk behaviour; sexually transmitted infections; HIV
7.  Frequency, Patterns and Preferences of Lubricant Use During Anal Intercourse Within Male Sexual Partnerships in Lima, Peru: Implications for a Rectal Microbicide HIV Prevention Intervention 
AIDS care  2012;25(5):579-585.
Understanding current practices of lubricant use during anal intercourse can help to assess the contexts for the introduction of topical rectal microbicides as an HIV prevention tool for men who have sex with men (MSM). We used quantitative and qualitative methods to assess: current patterns of lubricant use; preferred characteristics of commercial lubricant formulations; and social and behavioral contexts of lubricant use within male sexual partnerships in Lima, Peru. Between 2007 and 2008, we conducted a quantitative behavioral survey with 547 MSM followed by qualitative individual and group interviews with 36 MSM from Lima, Peru. Approximately half of all participants in the quantitative survey (50.3%) reported using commercial lubricant during intercourse occasionally or consistently during the preceding two months, with lack of availability at the time of intercourse the most commonly reported reason for non-use. No clear preferences regarding the color, smell, taste, or viscosity of commercial lubricants were identified, and all participants who reported using a commercial lubricant used the same product (“Love-Lub”). In the qualitative analysis, participants characterized lubricant use as a sexual practice consistently controlled by the receptive partner, who typically obtained and applied lubricant independently, with or without the consent of the insertive partner. Quantitative findings supported this differential pattern of lubricant use, with men who reported sexual identities or roles consistent with receptive anal intercourse, including unprotected receptive intercourse, more likely to report lubricant use than MSM who claimed an exclusively insertive sexual role. Given the social, behavioral, and biological factors contributing to increased vulnerability for HIV and STI acquisition by the receptive partner in anal intercourse, delivery of a topical rectal microbicide as a lubricant formulation could provide an important HIV prevention resource for at-risk MSM in Lima, Peru.
doi:10.1080/09540121.2012.726335
PMCID: PMC3556347  PMID: 23082796
8.  Commercial sex and risk of HIV, syphilis, and herpes simplex virus-2 among men who have sex with men in six Chinese cities 
BMC Infectious Diseases  2016;16:765.
Background
Men who have sex with men (MSM) are at high risk of HIV and sexually transmitted infections (STIs) in China and globally. Engaging in commercial sex put them at even greater risk. This study estimated the prevalence of HIV/STIs among three subgroups of MSM: MSM who sold sex (MSM-selling), MSM who bought sex (MSM-buying), and non-commercial MSM (NC-MSM) and evaluated the relationship between commercial sex and HIV/STIs.
Methods
We conducted a cross-sectional survey among MSM in six Chinese cities (Shenyang, Ji’nan, Changsha, Zhengzhou, Nanjing, and Kunming) from 2012 to 2013. Data on socio-demographics and sexual behaviors were collected. Serological tests were conducted to detect HIV, syphilis, and human simplex virus type 2 (HSV-2).
Results
Of 3717 MSM, 6.8% were engaged in commercial sex. The overall prevalence of HIV, syphilis and HSV-2 infections was 11.1, 8.8 and 12.1%, respectively. MSM-selling had higher prevalence of HIV (13.4%), syphilis (12.1%) and HSV-2 (17.9%) than NC-MSM (10.9, 8.7 and 11.9% for HIV, syphilis and HSV-2, respectively), though the differences are not statistically significant. Among MSM-selling, HIV prevalence was significantly higher for those who found sex partners via Internet than those did not (19.4% vs. 8.1%, P = 0.04). Compared to NC-MSM, MSM-selling were more likely to use recreation drugs (59.3% vs. 26.3%), have unprotected anal intercourse (77.9% vs. 61.7%), and have ≥10 male sex partners (46.2% vs. 6.2%) in the past 6 months (each P < 0.05).
Conclusions
All three subgroups of MSM in six large Chinese cities have high prevalence of HIV/STIs. Those who sell sex only have a particularly high risk of acquiring and transmitting disease, and therefore, they should be considered as a priority group in HIV/STIs surveillance and intervention programs.
Electronic supplementary material
The online version of this article (doi:10.1186/s12879-016-2130-x) contains supplementary material, which is available to authorized users.
doi:10.1186/s12879-016-2130-x
PMCID: PMC5178086  PMID: 28003032
Men who have sex with men; Commercial sex; HIV; Sexually transmitted infection China
9.  Homosexual men's HIV related sexual risk behaviour in Scotland 
Sexually Transmitted Infections  1999;75(4):242-246.
OBJECTIVE: To date, the epidemic of HIV infection in Scotland has been primarily associated with injecting drug use. However, the epidemiology of HIV in Scotland changed in the late 1980s, with homosexual men becoming the largest group at risk of HIV infection and AIDS. Our aim was to describe homosexual men's sexual risk behaviours for HIV infection in a sample of men in Scotland's two largest cities. DESIGN/SETTING: Trained sessional research staff administered a short self completed questionnaire, to homosexual men present in all of Glasgow's and Edinburgh's "gay bars," during a 1 month period. SUBJECTS: A total of 2276 homosexual men participated, with a response rate of 78.5%. Of these, 1245 were contacted in Glasgow and 1031 in Edinburgh. MAIN OUTCOME MEASURES: Sociodemographic data, recent (past year) sexual behaviour, information on last occasion of anal intercourse with and without condoms, and sexual health service use. RESULTS: Anal intercourse is a common behaviour; 75% of men have had anal intercourse in the past year. A third of our sample report anal intercourse with one partner in the past year, but 42% have had anal intercourse with multiple partners. Over two thirds of the total population have not had any unprotected anal intercourse (UAI) in the past year and a quarter of the sample have had UAI with one partner only. 8% report UAI with two or more partners. More men in Edinburgh (17% v 10%) reported unprotected sex with casual partners only, but more men in Glasgow (29% v 20%) reported UAI with both casual and regular partners (chi 2 = 12.183 p < 0.02). Multiple logistical regression found that odds of UAI are 30% lower for men with degree level education and 40% lower for men who claim to know their own HIV status, whereas they are 40% higher for those who have been tested for HIV and 48% higher for infrequent visitors to the "gay scene". Men who have had an STI in the past year are 2.4 times more likely to report UAI than those who have not. Men with a regular partner were significantly more likely to report UAI, as were those who had known their partner for longer, and who claimed to know their partner's antibody status. CONCLUSION: On the basis of current sexual risk taking, the epidemic of HIV among homosexual men in Scotland will continue in future years. The data reported here will prove useful both for surveillance of sexual risk taking, and the effectiveness of Scotland-wide and UK-wide HIV prevention efforts among homosexual men. 



PMCID: PMC1758219  PMID: 10615310
10.  Socialization Patterns and Their Association with Unprotected Anal Intercourse, HIV, and Syphilis Among High-Risk Men Who Have Sex with Men and Transgender Women in Peru 
AIDS and behavior  2014;18(10):2030-2039.
The association of socialization patterns with unprotected anal intercourse (UAI) and HIV/STI prevalence remains underexplored in men who have sex with men (MSM) and transgender women (TW) in developing country settings. We evaluated the correlation of UAI, HIV, and syphilis with MSM/TW venue attendance and social network size among high-risk MSM and TW in Peru according to self-reported sexual identity. Frequency of venue attendance and MSM/TW social network size were lowest among heterosexual MSM and highest among TW respondents. Attendance (frequent or occasional) at MSM/TW venues was associated with increased odds of insertive UAI among heterosexual participants. Frequent venue attendance was associated with increased odds of receptive UAI among gay/homosexual, bisexual, and TW participants. Further investigation of the differing socialization patterns and associations with HIV/STI transmission within subgroups of Peruvian MSM and TW will enable more effective prevention interventions for these populations.
doi:10.1007/s10461-014-0787-y
PMCID: PMC4174724  PMID: 24788782
Men who have sex with men; transgender women; unprotected anal intercourse; HIV; socialization patterns
11.  Unprotected sex among men who have sex with men living with HIV in Brazil: a cross-sectional study in Rio de Janeiro 
BMC Public Health  2014;14:379.
Background
Many countries are facing concentrated HIV epidemics among vulnerable populations, including men who have sex with men (MSM). Unprotected anal intercourse (UAI) is the main HIV transmission route among them and its understanding in the different cultures and how it relates to HIV transmission, re-infection and development of HIV antiretroviral resistance has important public health implications. Data on UAI among Brazilian MSM are scarce. This study aims to evaluate the prevalence and associated factors of UAI among HIV-infected MSM who had sex with seronegative or male partners with an unknown serostatus.
Method
A cross-sectional study nested in a cohort was conducted in Rio de Janeiro, Brazil. The one hundred and fifty five MSM included in the study answered an ACASI interview and provided biological samples. Generalized linear models were used to identify variables associated with UAI.
Results
Overall, UAI with an HIV-negative or unknown serostatus male partner was reported by 40.6% (63/155) of MSM. Lifetime sexual abuse or domestic violence was reported by 35.9%, being more frequent among MSM who reported UAI compared to those who did not (P = 0.001). Use of stimulants before sex was reported by 20% of the MSM, being slightly higher among those who reported UAI (27.0% vs. 15.2%; P = 0.072). Commercial sex was frequent among all MSM (48.4%). After multivariate modeling, the report of sexual abuse or domestic violence (OR = 2.70; 95% CI: 1.08-7.01), commercial sex (OR = 2.28; 95% CI: 1.04- 5.10), the number of male sexual partners (p = 0.039) and exclusively receptive anal intercourse (OR = 0.21; 95% CI: 0.06-0.75) remained associated with UAI. CD4 levels, HIV viral load and antiretroviral therapy were not associated with UAI.
Conclusion
The UAI prevalence found with negative or unknown HIV status partners points out that other interventions are needed as additional prevention tools to vulnerable MSM. The main factors associated with UAI were a lifetime history of violence, commercial sex and the number of male sexual partners. This clustering of different behavioral, health and social problems in this population reinforce the need of a comprehensive approach on treating and preventing HIV among MSM.
doi:10.1186/1471-2458-14-379
PMCID: PMC4005457  PMID: 24742202
Men who have sex with men; HIV/AIDS; Unprotected anal intercourse; Low and middle income countries
12.  PREDICTORS OF UNPROTECTED SEX AMONG MEN WHO HAVE SEX WITH MEN IN BEIJING, CHINA 
Li, X | Shi, W | Li, D | Ruan, Y | Jia, Y | Vermund, SH | Zhang, Xiaoxi | Wang, C | Liu, Y | Yu, M | Xing, H | Hong, K | Shao, Y
To estimate the prevalence of HIV and syphilis and to assess the predictors of unprotected anal intercourse (UAI) among men who have sex with men (MSM) in Beijing, a community-based survey recruited MSM in 2005 through internet advertisement, community outreach, and peer referral. Demographic, sexual, and HIV risk behavioral information were collected. Serospecimens were tested for HIV and syphilis infections. Of the 526 participants, 3.2% were HIV-positive, 11.2% syphilis-positive, 50% and 43.3% had UAI with regular and casual sex partners, respectively. Participants practicing UAI with regular male partners were independently associated with lower monthly income (adjusted odds ratio-AOR, 1.7; 95% CI, 1.0–3.0) and encountering male sex partners at bathhouses, public washrooms, and parks (AOR, 2.2; 95% CI, 1.0–4.9). Participants practicing UAI with casual male partners were associated with encountering male sex partners at bathhouses, publics washrooms, and park (AOR, 3.0; 95% CI, 1.8–5.2) and more male sex partners having receptive anal intercourse (AOR, 1.8; 95% CI, 1.1–2.9), and was inversely associated with receiving money for sex with men (AOR, 0.3; 95% CI, 0.2–0.7). Professional male sex workers were less likely to practice UAI in Beijing, suggesting the benefits of educational outreach to date. Further education, condom promotion, and prevention of sexually transmitted infections should be intensified urgently to combat the rising HIV epidemic among MSM in Beijing.
PMCID: PMC2730761  PMID: 18567448
13.  Sexual Seroadaptation: Lessons for Prevention and Sex Research from a Cohort of HIV-Positive Men Who Have Sex with Men 
PLoS ONE  2010;5(1):e8831.
Background
Surveillance data on sexually transmitted infections (STIs) and behavioral characteristics identified in studies of the risk of seroconversion are often used as to track sexual behaviors that spread HIV. However, such analyses can be confounded by “seroadaptation”—the restriction of unprotected anal intercourse (UAI), especially unprotected insertive UAI, to seroconcordant partnerships.
Methods
We utilized sexual network methodology and repeated-measures statistics to test the hypothesis that seroadaptive strategies reduce the risk of HIV transmission despite numerous partnerships and frequent UAI.
Principal Findings
In a prospective cohort study of HIV superinfection including 168 HIV-positive men who have sex with men (MSM), we found extensive seroadaptation. UAI was 15.5 times more likely to occur with a positive partner than a negative one (95% confidence interval [CI], 9.1–26.4). Receptive UAI was 4.3 times more likely in seroconcordant partnerships than with negative partners (95% CI, 2.8–6.6), but insertive UAI was 13.6 times more likely with positives (95% CI, 7.2–25.6). Our estimates suggest that seroadaptation reduced HIV transmissions by 98%.
Conclusion
Potentially effective HIV prevention strategies, such as seroadaptation, have evolved in communities of MSM before they have been recognized in research or discussed in the public health forum. Thus, to be informative, studies of HIV risk must be designed to assess seroadaptive behaviors rather than be limited to individual characteristics, unprotected intercourse, and numbers of partners. STI surveillance is not an effective indicator of trends in HIV incidence where there are strong patterns of seroadaptation.
doi:10.1371/journal.pone.0008831
PMCID: PMC2809110  PMID: 20098616
14.  HIV/STIs risks between migrant MSM and local MSM: a cross-sectional comparison study in China 
PeerJ  2016;4:e2169.
Background. Internal migration plays a significant role in China’s HIV epidemic. However, few studies have directly compared migrant men who have sex with men (MSM) with local MSM with regard to HIV/sexually transmitted infections (STIs) risks.
Methods. We conducted a study in Guangzhou, China, with the aim of understanding the differences in HIV/STIs risks between migrant MSM and local MSM. A cross-sectional study was conducted among 273 migrant MSM and 249 local MSM in Guangzhou, China. Their behavioral and serologic data on HIV/syphilis were collected and compared between the two groups. A multivariate logistic regression was used to estimate the associations between HIV/STIs risks and migratory status.
Results. Migrant MSM, compared to local MSM, have higher odds of reporting unprotected anal intercourse (UAI) (OR = 1.4; 95% CI [0.9–2.0]) and having multiple homosexual partners (OR = 1.2; 95% CI [0.8–1.8]). A lower rate of condom use at homosexual debut was reported in migrant MSM than in local MSM (OR = 0.7; 95% CI [0.5–0.9]). Migrant MSM have less odds of reporting HIV/STIs testing in the previous 6 months relative to local MSM (OR = 0.5; 95% CI [0.4–0.8]). In addition, migrant MSM demonstrated a lower level of HIV knowledge than local MSM (OR = 0.4; 95% CI [0.2–0.8]).
Conclusion. Migrant MSM are more likely to engage in sexual risk behaviors, report a lower level of HIV knowledge and have less access to HIV/STIs testing. Further comprehensive interventions targeting migrant MSM are urged.
doi:10.7717/peerj.2169
PMCID: PMC4950534  PMID: 27478695
HIV/STIs risk; Migration; MSM; Comparison
15.  Increasing HIV and Decreasing Syphilis Prevalence in a Context of Persistently High Unprotected Anal Intercourse, Six Consecutive Annual Surveys among Men Who Have Sex with Men in Guangzhou, China, 2008 to 2013 
PLoS ONE  2014;9(7):e103136.
Introduction
Previous studies have reported a possibly increasing HIV prevalence among men who have sex with men (MSM) in China. However there have been limited systematic analyses of existing surveillance data to learn the trend of HIV prevalence and factors driving the trend. The aims of this study were to examine the trend of HIV prevalence among MSM in Guangzhou and to explore the role of unprotected anal intercourse (UAI) in the trend.
Methods
Snow-ball sampling was applied in the subject recruitment for the annual serological and behavioral surveys among MSM from 2008 to 2013. Data collected in the behavioral survey include demographic information, HIV related sexual behavior with men and women, access to HIV prevention services, and symptoms of sexually transmitted infections. Chi-square test was used to analyze the trend of HIV prevalence. Multivariate logistic regression was conducted to test the factors associated with HIV infection.
Results
HIV prevalence increased significantly from 5.0% in 2008 to 11.4% in 2013 while syphilis prevalence decreased from 17.4% to 3.3% in the same period. UAI rates were high and stable in every single year, ranging from 54.5% to 62.0%. Those who were having UAI (OR = 1.80, 95% confidence interval (CI): 1.26–2.58), being migrants, having more than 10 partners, and infected with syphilis had higher risk for HIV infection.
Conclusions
HIV epidemic is expanding in Guangzhou. The persistently high UAI may have played a major role in the increasing trend of HIV prevalence. Targeted prevention program should be conducted among MSM who are migrants, low educational level, syphilis infected, or having multiple partners to encourage HIV test and change UAI behavior. The general high UAI calls for tailored intervention program to promote healthy culture and form a safe sex social norm in the MSM community.
doi:10.1371/journal.pone.0103136
PMCID: PMC4111575  PMID: 25061936
16.  Anal human papillomavirus infection among HIV-infected and uninfected men who have sex with men in Beijing, China 
To determine prevalence, genotypes and predictors of anal human papillomavirus (HPV) among HIV-infected and uninfected men who have sex with men (MSM) in Beijing, China. In 2010–2011, we recruited MSM (age range 18–61; median 28 years) through peer volunteers, and collected demographic/behavioral information via interviewer-administrated questionnaires. Trained health workers collected anal swabs for HPV genotyping by PCR and blood samples for HIV/syphilis serologies . We obtained anal specimens from 212 HIV-infected and 459 HIV-uninfected participants. Among HIV-infected MSM, 82.1% were HPV-infected vs. 57.5% in HIV-uninfected (p<0.01). HIV-infected men had the greatest likelihood of multiple types: 17.9% uninfected; 36.3% with one type; 36.8% with 2–3; 9.0% with >4. Oncogenic HPV prevalence was higher among HIV- infected (61.3%) than uninfected participants (39.7%; p<0.01). HIV-uninfected MSM reporting always using condoms during insertive anal intercourse (past 6 months) were less likely to be HPV-infected (OR=0.49, 95%CI: 0.31–0.77). Among HIV-uninfected MSM, HPV infection was associated with unprotected receptive anal intercourse (past 6 months; OR=1.92, 95%CI: 1.19–3.11) and being forced to have sex (previous year; OR=3.32, 95%CI: 1.10–10.0). Multivariable logistic analysis among HIV infected MSM suggested that unprotected oral intercourse (past 6 months) was associated with HPV (adjusted OR=2.12, 95%CI: 1.00–4.48). Syphilis occurred in 55.8% of HIV-infected/HPV-infected, 50.0% of HIV-infected/HPV-uninfected, 19.6% of HIV-uninfected/HPV-infected, and 13.0% of HIV-uninfected/HPV-uninfected MSM. HPV anal infections were more common among HIV-infected than uninfected MSM in China, including oncogenic and multiple types. Unprotected oral and receptive anal sex were significant HPV risk factors. Promotion of safer sex and HPV vaccination is strongly recommended among MSM.
doi:10.1097/QAI.0b013e31829b6298
PMCID: PMC3780393  PMID: 23732908
Human papillomavirus; HIV; syphilis; genotype; men who have sex with men; China
17.  Consistently High Unprotected Anal Intercourse (UAI) and factors correlated with UAI among men who have sex with men: implication of a serial cross-sectional study in Guangzhou, China 
BMC Infectious Diseases  2014;14:696.
Background
China experiencing an increasing HIV epidemic among men who have sex with men (MSM), and unprotected anal intercourse (UAI) has played a key role in this process. The aims of this study were to examine the trend of UAI and to explore the factors correlated with UAI among MSM in Guangzhou, China.
Methods
Data from 2008 to 2013 were retrieved from the annual serological and behavioral surveys system. We collected information on demographic, HIV related sexual behavior with men and women, access to HIV prevention services, and symptoms of sexually transmitted infections. Chi-square test was used to examine the similarity of the participants during the study period. Univariate and multivariate logistic regression were conducted to test the factors associated with UAI. Trend test was used to check the change of UAI in different characteristic stratums during the study period.
Results
In total, 58.4% (range from 54.5% to 62.0%) of the participants reported that they engaged in UAI in the past six months. Participants who aged less than 20 [Adjusted Odds Ratio (AOR): 2.22, 95% Confidential Interval (CI): 1.07-4.61], only attended elementary school (or less) (AOR: 1.41, 95% CI: 1.04-1.90), cohabiting with male partner (AOR: 2.15, 95% CI: 1.66-2.79), divorced or widowed (AOR: 2.80, 95% CI: 1.54-5.07), did not test for HIV in the past year (AOR: 1.36, 95% CI: 1.12-1.65), and had 10 or more partners in the past six months (AOR: 1.85, 95% CI: 1.18-2.91) had higher odds of UAI. However, the proportions of UAI were stable in different stratums during the study period.
Conclusions
The proportion of MSM engaged in UAI was consistently high during the study period. Effective intervention strategies, which include but not limit to risk reduction counseling and testing services, are urgently needed to bring down the risk behaviors of the MSM in Guangzhou, in order to control HIV/STIs epidemic in this specific population.
doi:10.1186/s12879-014-0696-8
PMCID: PMC4279965  PMID: 25519034
Unprotected anal intercourse (UAI); Men who have sex with men (MSM); Human immunodeficiency virus (HIV); Trend; Serial cross-sectional study; China
18.  Risk factors for HIV and STI diagnosis in a community-based HIV/STI testing and counselling site for men having sex with men (MSM) in a large German city in 2011–2012 
Background
In recent years community-based voluntary counselling and testing sites (CB-VCT) for men having sex with men (MSM) have been established in larger cities in Germany to offer more opportunities for HIV testing. Increasingly, CB-VCTs also offer testing for other bacterial sexually transmitted infections. In Hamburg, tests in CB-VCTs are offered free and anonymously. Data on demographics and sexual risk behaviours are collected with a paper questionnaire.
Methods
Questionnaire data from the MSM CB-VCT in Hamburg were linked with serological test results for HIV and syphilis, and with rectal and pharyngeal swab results for gonorrhoea and chlamydia. MSM were defined as males reporting male sex partners. CB-VCT clients were characterized demographically, and associations between sexual behaviour variables and diagnosis of HIV and sexually transmitted infections (STI) were analysed by bivariate and multivariate logistic regression analysis.
Results
Among the male clients of the CB-VCT in 2011–2012 who were tested for HIV or any STI 1476 reported male sex partners. Unprotected anal intercourse (UAI) was reported as reason for testing by 61% of the clients. Forty-one of 1413 clients testing for HIV were tested positive (2.9%). Twenty-four of 1380 clients testing for syphilis required treatment (1.7%). Tests for simultaneous detection of N. gonorrhoea and Chlamydia trachomatis were conducted on 882 pharyngeal and 642 rectal swabs, revealing 58 (=6.6%) pharyngeal and 71 (=11.1%) rectal infections with one or both pathogens. In multivariate logistic regression analysis number of partners, UAI (OR=2.42) and relying on visual impression when selecting sex partners (OR = 2.92) were associated with increased risks for diagnosis of syphilis or a rectal STI. Syphilis or rectal STI diagnosis (OR=4.52) were associated with increased risk for HIV diagnosis.
Conclusions
The MSM CB-VCT in Hamburg reaches clients at high risk for HIV and STIs. The diagnosis of syphilis or a rectal STI was associated with increased odds of testing positive for HIV. Due to the high prevalence of curable bacterial STI among clients and because syphilis and rectal bacterial STI may facilitate HIV transmission, MSM asking for HIV tests in CB-VCTs should also be offered tests for other bacterial STIs.
doi:10.1186/s12879-014-0738-2
PMCID: PMC4307229  PMID: 25582975
HIV infection; Men who have sex with men-MSM; Sexually transmitted infections; Community based voluntary counselling and testing
19.  Long-Term Biological and Behavioural Impact of an Adolescent Sexual Health Intervention in Tanzania: Follow-up Survey of the Community-Based MEMA kwa Vijana Trial 
PLoS Medicine  2010;7(6):e1000287.
David Ross and colleagues conduct a follow-up survey of the community-based MEMA kwa Vijana (“Good things for young people”) trial in rural Tanzania to assess the long-term behavioral and biological impact of an adolescent sexual health intervention.
Background
The ability of specific behaviour-change interventions to reduce HIV infection in young people remains questionable. Since January 1999, an adolescent sexual and reproductive health (SRH) intervention has been implemented in ten randomly chosen intervention communities in rural Tanzania, within a community randomised trial (see below; NCT00248469). The intervention consisted of teacher-led, peer-assisted in-school education, youth-friendly health services, community activities, and youth condom promotion and distribution. Process evaluation in 1999–2002 showed high intervention quality and coverage. A 2001/2 intervention impact evaluation showed no impact on the primary outcomes of HIV seroincidence and herpes simplex virus type 2 (HSV-2) seroprevalence but found substantial improvements in SRH knowledge, reported attitudes, and some reported sexual behaviours. It was postulated that the impact on “upstream” knowledge, attitude, and reported behaviour outcomes seen at the 3-year follow-up would, in the longer term, lead to a reduction in HIV and HSV-2 infection rates and other biological outcomes. A further impact evaluation survey in 2007/8 (∼9 years post-intervention) tested this hypothesis.
Methods and Findings
This is a cross-sectional survey (June 2007 through July 2008) of 13,814 young people aged 15–30 y who had attended trial schools during the first phase of the MEMA kwa Vijana intervention trial (1999–2002). Prevalences of the primary outcomes HIV and HSV-2 were 1.8% and 25.9% in males and 4.0% and 41.4% in females, respectively. The intervention did not significantly reduce risk of HIV (males adjusted prevalence ratio [aPR] 0.91, 95%CI 0.50–1.65; females aPR 1.07, 95%CI 0.68–1.67) or HSV-2 (males aPR 0.94, 95%CI 0.77–1.15; females aPR 0.96, 95%CI 0.87–1.06). The intervention was associated with a reduction in the proportion of males reporting more than four sexual partners in their lifetime (aPR 0.87, 95%CI 0.78–0.97) and an increase in reported condom use at last sex with a non-regular partner among females (aPR 1.34, 95%CI 1.07–1.69). There was a clear and consistent beneficial impact on knowledge, but no significant impact on reported attitudes to sexual risk, reported pregnancies, or other reported sexual behaviours. The study population was likely to have been, on average, at lower risk of HIV and other sexually transmitted infections compared to other rural populations, as only youth who had reached year five of primary school were eligible.
Conclusions
SRH knowledge can be improved and retained long-term, but this intervention had only a limited effect on reported behaviour and no significant effect on HIV/STI prevalence. Youth interventions integrated within intensive, community-wide risk reduction programmes may be more successful and should be evaluated.
Trial Registration
ClinicalTrials.gov NCT00248469
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Every year, about 2.5 million people become infected with the human immunodeficiency virus (HIV), the virus that causes AIDS. HIV is most often spread through unprotected sex with an infected partner, so individuals can reduce their risk of HIV infection by abstaining from sex, by delaying first sex, by having few partners, and by always using a condom. And, because nearly half of new HIV infections occur among youths (15- to 24-year-olds), programs targeted at adolescents that encourage these protective behaviors could have a substantial impact on the HIV epidemic. One such program is the MEMA kwa Vijana (“Good things for young people”) program in rural Tanzania. This program includes in-school sexual and reproductive health (SRH) education for pupils in their last three years of primary education (12- to 15-year-olds) that provides them with the knowledge and skills needed to delay sexual debut and to reduce sexual risk taking. Between 1999 and 2002, the program was trialed in ten randomly chosen rural communities in the Mwanza Region of Tanzania; ten similar communities that did not receive the intervention acted as controls. Since 2004, the program has been scaled up to cover more communities.
Why Was This Study Done?
Although the quality and coverage of the MEMA kwa Vijana program was good, a 2001/2002 evaluation found no evidence that the intervention had reduced the incidence of HIV (the proportion of the young people in the trial who became HIV positive during the follow-up period) or the prevalence (the proportion of the young people in the trial who were HIV positive at the end of the follow-up period) of herpes simplex virus 2 (HSV-2, another sexually transmitted virus). However, the evaluation found improvements in SRH knowledge, in reported sexual attitudes, and in some reported sexual behaviors. Evaluations of other HIV prevention programs in other developing countries have also failed to provide strong evidence that such programs decrease the risk of HIV infection or other biological outcomes such as the frequency of other sexually transmitted infections or pregnancies, even when SRH knowledge improves. One possibility is that it takes some time for improved SRH knowledge to be reflected in true changes in sexual behavior and in HIV prevalence. In this follow-up study, therefore, researchers investigate the long-term impact of the MEMA kwa Vijana program on HIV and HSV-2 prevalence and ask whether the improvement in knowledge, reported attitudes and sexual risk behaviours seen at the 3-year follow up has persisted.
What Did the Researchers Do and Find?
In 2007/8, the researchers surveyed nearly 14,000 young people who had attended the trial schools between 1999 and 2002. Each participant had their HIV and HSV-2 status determined and answered questions (for example, “can HIV be caught by sexual intercourse (making love) with someone,” and “if a girl accepts a gift from a boy, must she agree to have sexual intercourse (make love) with him?”) to provide three composite sexual knowledge scores and one composite attitude score. 1.8% of the male and 4.0% of the female participants were HIV positive; 25.9% and 41.4% of the male and female participants, respectively, were HSV-2 positive. The prevalences were similar among the young people whose trial communities had been randomly allocated to receive the MEMA kwa Vijana Program and those whose communities had not received it, indicating that the MEMA kwa Vijana intervention program had not reduced the risk of HIV or HSV-2. The intervention program was associated, however, with a reduction in the proportion of men reporting more than four sexual partners in their lifetime and with an increase in reported condom use at last sex with a non-regular partner among women. Finally, although the intervention had still increased SRH knowledge, it now had had no impact on reported attitudes to sexual risk, reported pregnancies, or other reported risky sexual behaviors beyond what might have happened due to chance.
What Do These Findings Mean?
These findings indicate that, in the MEMA kwa Vijana trial, SRH knowledge improved and that this improved knowledge was retained for many years. Disappointingly, however, this intervention program had only a limited effect on reported sexual behaviors and no effect on HIV and HSV-2 prevalence at the 9-year follow-up. Although these findings may not be generalizable to other adolescent populations, they suggest that intervention programs that target only adolescents might not be particularly effective. Young people might find it hard to put their improved skills and knowledge into action when challenged, for example, by widespread community attitudes such as acceptance of older male–younger female relationships. Thus, the researchers suggest that the integration of youth HIV prevention programs within risk reduction programs that tackle sexual norms and expectations in all age groups might be a more successful approach and should be evaluated.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000287.
This study is further discussed in a PLoS Medicine Perspective by Rachel Jewkes
More information about the MEMA kwa Vijana program is available at their Web site
Information is available from the Programme for Research and Capacity Building in Sexual and Reproductive Health and HIV in Developing Countries on recent and ongoing research on HIV infection and other STIs
Information is available from the World Health Organization on HIV and on the health of young people
Information on HIV is available from UNAIDS
Information on HIV in children and adolescents is available from UNICEF
Information on HIV prevention interventions in the education sector is available from UNESCO
Information on HIV infection and AIDS is available from the US National Institute of Allergy and Infectious Diseases
The US Centers for Disease Control and Prevention provide information on HIV/AIDS and on HIV/AIDS among youth (in English and Spanish)
HIV InSitehas comprehensive information on all aspects of HIV/AIDS, including links to information on the prevention of HIV/AIDS
Information is available from Avert, an international AIDS charity, on many aspects of HIV/AIDS, including information on HIV and AIDS prevention and AIDS and sex education (in English and Spanish)
doi:10.1371/journal.pmed.1000287
PMCID: PMC2882431  PMID: 20543994
20.  International mobility, sexual behaviour and HIV-related characteristics of men who have sex with men residing in Belgium 
BMC Public Health  2013;13:968.
Background
European men who have sex with men (MSM) continue to be disproportionally affected by the human immunodeficiency virus (HIV). Several factors are contributing to the rates of new HIV infections among MSM. The aim of this study was to investigate the potential role of travel behaviour and sexual mobility in the spread of HIV and sexually transmitted infections (STI) among European MSM.
Methods
Belgian data from the first pan-European MSM internet survey EMIS was used (n=3860) to explore individual and contextual determinants of sexual behaviour among MSM, who resided in Belgium at the time of data collection and who reported having had sexual contact abroad in the last 12 months. Descriptive and bivariate analyses were performed. Odds ratios and 95% confidence intervals were calculated by means of logistic regression.
Results
MSM who practiced unprotected anal intercourse UAI during their last sexual encounter abroad were less likely to be living in a large city (OR:0.62, 95% CI:0.45-0,86, p<0.01) and more likely to be HIV positive (OR:6.20, 95% CI:4.23-9.06, p<0.001) ), to have tested HIV positive in the last 12 months (OR:3.07, 95% CI:1.07-8.80, p<0.05), to have been diagnosed with any STI in the last 12 months (OR:2.55; 95% CI:1.77-3.67, p<0.05), to have used party drugs (OR:2.22, 95% CI:1.59-3.09, p<0.001), poppers (OR:1.52, 95% CI:1.07-2.14, p<0.001) and erection enhancing substances (OR:2.23, 95% CI:1.61-3.09, p<0.001) compared to MSM who did not have UAI with their last sexual partner abroad. Men having had UAI in the last 12 months were more likely to have done so in a neighbouring country of Belgium (OR:1.66, 95% CI:1.21-2.29, p<0.001). Different sexual behavioural patterns related to condom use and drug use were identified according to HIV test status among travelling men.
Conclusions
The results of this study provide evidence for the role of international mobility and sexual behavior while travelling, in the spread of HIV and STI among MSM in Europe. Further, the findings underline the need for development of European cross-border HIV and STI interventions with coherent messages and prevention policies for MSM.
doi:10.1186/1471-2458-13-968
PMCID: PMC3853336  PMID: 24139406
HIV infection; Men who have sex with Men (MSM); Travel
21.  Seroadaptive Practices: Association with HIV Acquisition among HIV-Negative Men Who Have Sex with Men 
PLoS ONE  2012;7(10):e45718.
Background
Although efficacy is unknown, many men who have sex with men (MSM) attempt to reduce HIV risk by adapting condom use, partner selection, or sexual position to the partner’s HIV serostatus. We assessed the association of seroadaptive practices with HIV acquisition.
Methodology/Principal Findings
We pooled data on North American MSM from four longitudinal HIV-prevention studies. Sexual behaviors reported during each six-month interval were assigned sequentially to one of six mutually exclusive risk categories: (1) no unprotected anal intercourse (UAI), (2) having a single negative partner, (3) being an exclusive top (only insertive anal sex), (4) serosorting (multiple partners, all HIV negative), (5) seropositioning (only insertive anal sex with potentially discordant partners), and (6) UAI with no seroadaptive practices. HIV antibody testing was conducted at the end of each interval. We used Cox models to evaluate the independent association of each category with HIV acquisition, controlling for number of partners, age, race, drug use, and intervention assignment. 12,277 participants contributed to 60,162 six-month intervals with 663 HIV seroconversions. No UAI was reported in 47.4% of intervals, UAI with some seroadaptive practices in 31.8%, and UAI with no seroadaptive practices in 20.4%. All seroadaptive practices were associated with a lower risk, compared to UAI with no seroadaptive practices. However, compared to no UAI, serosorting carried twice the risk (HR = 2.03, 95%CI:1.51–2.73), whereas seropositioning was similar in risk (HR = 0.85, 95%CI:0.50–1.44), and UAI with a single negative partner and as an exclusive top were both associated with a lower risk (HR = 0.56, 95%CI:0.32–0.96 and HR = 0.55, 95%CI:0.36–0.84, respectively).
Conclusions/Significance
Seroadaptive practices appear protective when compared with UAI with no seroadaptive practices, but serosorting appears to be twice as risky as no UAI. Condom use and limiting number of partners should be advocated as first-line prevention strategies, but seroadaptive practices may be considered harm-reduction for men at greatest risk.
doi:10.1371/journal.pone.0045718
PMCID: PMC3463589  PMID: 23056215
22.  Risk Factors for HIV and Unprotected Anal Intercourse among Men Who Have Sex with Men (MSM) in Almaty, Kazakhstan 
PLoS ONE  2012;7(8):e43071.
Introduction
Men who have sex with men (MSM) are at high risk for HIV infection. MSM in Central Asia, however, are not adequately studied to assess their risk of HIV transmission. Methods: This study used respondent driven sampling methods to recruit 400 MSM in Almaty, the largest city in Kazakhstan, into a cross-sectional study. Participation involved a one-time interviewer-administered questionnaire and rapid HIV screening test. Prevalence data were adjusted for respondent network size and recruitment patterns. Multivariate logistic regression was used to investigate the association between HIV and selected risk factors, and unprotected anal intercourse (UAI) and selected risk factors.
Results
After respondent driven sampling (RDS) weighted analysis, 20.2% of MSM were HIV-positive, and 69.0% had unprotected sex with at least one male partner in the last 12 months. Regression analysis showed that HIV infection was associated with unprotected receptive anal sex (AOR: 2.00; 95% CI: 1.04–3.84). Having unprotected anal intercourse with male partners, a measure of HIV risk behaviors, was associated with being single (AOR: 0.38; 95% CI: 0.23–0.64); very difficult access to lubricants (AOR: 11.08; 95% CI: 4.93–24.91); STI symptoms (AOR: 3.45; 95% CI: 1.42–8.40); transactional sex (AOR: 3.21; 95% CI: 1.66–6.22); and non-injection drug use (AOR: 3.10; 95% CI: 1.51–6.36).
Conclusions
This study found a high HIV prevalence among MSM in Almaty, and a population of MSM engaging in multiple high-risk behavior in Almaty. Greater access to HIV education and prevention interventions is needed to limit the HIV epidemic among MSM in Almaty.
doi:10.1371/journal.pone.0043071
PMCID: PMC3427329  PMID: 22937013
23.  Are HIV Epidemics among Men Who Have Sex with Men Emerging in the Middle East and North Africa?: A Systematic Review and Data Synthesis 
PLoS Medicine  2011;8(8):e1000444.
A systematic review by Laith Abu-Raddad and colleagues collates and analyzes the epidemiology of HIV among men who have sex with men in Middle Eastern and North African countries.
Background
Men who have sex with men (MSM) bear a disproportionately higher burden of HIV infection than the general population. MSM in the Middle East and North Africa (MENA) are a largely hidden population because of a prevailing stigma towards this type of sexual behavior, thereby limiting the ability to assess infection transmission patterns among them. It is widely perceived that data are virtually nonexistent on MSM and HIV in this region. The objective of this review was to delineate, for the first time, the evidence on the epidemiology of HIV among MSM in MENA.
Methods and Findings
This was a systematic review of all biological, behavioral, and other related data on HIV and MSM in MENA. Sources of data included PubMed (Medline), international organizations' reports and databases, country-level reports and databases including governmental and nongovernmental organization publications, and various other institutional documents. This review showed that onsiderable data are available on MSM and HIV in MENA. While HIV prevalence continues at low levels among different MSM groups, HIV epidemics appear to be emerging in at least few countries, with a prevalence reaching up to 28% among certain MSM groups. By 2008, the contribution of MSM transmission to the total HIV notified cases increased and exceeded 25% in several countries. The high levels of risk behavior (4–14 partners on average in the last six months among different MSM populations) and of biomarkers of risks (such as herpes simplex virus type 2 at 3%–54%), the overall low rate of consistent condom use (generally below 25%), the relative frequency of male sex work (20%–76%), and the substantial overlap with heterosexual risk behavior and injecting drug use suggest potential for further spread.
Conclusions
This systematic review and data synthesis indicate that HIV epidemics appear to be emerging among MSM in at least a few MENA countries and could already be in a concentrated state among several MSM groups. There is an urgent need to expand HIV surveillance and access to HIV testing, prevention, and treatment services in a rapidly narrowing window of opportunity to prevent the worst of HIV transmission among MSM in the Middle East and North Africa.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
AIDS first emerged in the early 1980s among gay men living in the US. But, as the disease rapidly spread, it became clear that AIDS also affects heterosexual men and women. Now three decades on, more than 30 million people are infected with HIV, the virus that causes AIDS. HIV is most often spread by having unprotected sex with an infected partner and, globally, most sexual transmission of HIV now occurs during heterosexual sex. However, 5%–10% of all new HIV infections still occur in men who have sex with men (MSM, a term that encompasses homosexual, bisexual, and transgender men, and heterosexual men who sometimes have sex with men). In some countries, male-to-male sexual contact remains the most important transmission route. Moreover, although the global prevalence of HIV infection (the proportion the world's population infected with HIV) has stabilized, the prevalence of HIV infection among MSM seems to be increasing in multiple countries and new and resurgent HIV epidemics among MSM populations are being frequently reported.
Why Was This Study Done?
In the US and the UK, the MSM population is visible and has helped to raise awareness about the risks of HIV transmission through male-to-male sexual contact. In many other countries, MSM are much less visible, fearing discrimination, stigmatization (being considered socially unacceptable) or arrest. In the Middle East and North Africa (MENA, a geographical region that encompasses countries that share historical, socio-cultural, linguistic and religious characteristics), MSM are the most hidden HIV risk group. Consequently, very little is known about HIV transmission patterns among MSM in MENA. Indeed, it is widely thought that there is virtually no information available on the epidemiology (causes, distribution, and control) of HIV among MSM in this region. In this systematic review and data synthesis, the researchers use predefined search criteria to identify all the published and unpublished data on the epidemiology of HIV among MSM in MENA and combine (synthesize) these data to produce a coherent picture of the HIV epidemic in this potentially key group of people for HIV transmission in this region.
What Did the Researchers Do and Find?
The researchers identified 26 articles and 51 other country-level reports and sources of data that included data on the prevalence of male-to-male sexual contact, HIV transmission, levels of high-risk behavior, and the extent of knowledge about HIV among MSM in MENA. The prevalence of HIV infection among MSM was low in most countries but high in others. For example, the infection rate in Pakistan was 27.6% among one MSM group. Importantly, there was some evidence of increasing HIV prevalence and emerging epidemics among MSM in the region. Thus, by 2008, MSM transmission was responsible for more than a quarter of notified cases of HIV in several countries. Worryingly, MSM were involved in several types of HIV-related high risk behavior. For example, they had, on average, between 4 and 14 sexual partners in the past six months, their rates of consistent condom use were generally below 25% and, in some countries, MSM frequently reported injecting drug use, another common mode of HIV transmission. In addition, 20%–75.5% of MSM exchanged sex for money and contact between MSM and female sex workers and other female sexual partners was often common. Finally, although the level of basic knowledge about HIV/AIDS was high, the level of comprehensive knowledge was limited with a high proportion of MSM perceiving their risk of contracting HIV as low.
What Do These Findings Mean?
These findings indicate that there is considerable and increasing data about HIV transmission and risk behavior among MSM in MENA. However, the quality of this evidence varies greatly. Little has been collected over time in individual populations and, because only the visible part of the MSM populations in many MENA countries has been sampled, these findings may not be representative of all MSM in this region. Nevertheless, these findings suggest that HIV epidemics are emerging among MSM in several MENA countries. Importantly, the high levels of risk behaviors practiced by many MSM in MENA mean that MSM could become the pivotal risk group for HIV transmission in this region in the next decade. There is, therefore, an urgent need to expand HIV surveillance and access to HIV testing, prevention and treatment services among MSM in this region to limit the size of the HIV epidemic.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000444.
Information about the status of the HIV epidemic in the Middle East and North Africa can be found in the World Bank/UNAIDS/WHO report Characterizing the HIV/AIDS epidemic in the Middle East and North Africa: Time for strategic action
Information about the global HIV epidemic among men who have sex with men can be found in the World Bank report The Global HIV Epidemics among Men Who Have Sex with Men
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
HIV InSite has comprehensive information on all aspects of HIV/AIDS, including information on HIV transmission and transmission in gay men and other MSM and on safer sex
Information is available from Avert, an international AIDS charity, on all aspects of HIV/AIDS, including information on HIV, AIDS and men who have sex with men and on HIV and AIDS prevention (in English and Spanish)
The US Centers for Disease Control and Prevention also have information about HIV/AIDS among men who have sex with men (in English and Spanish)
doi:10.1371/journal.pmed.1000444
PMCID: PMC3149074  PMID: 21829329
24.  The Comparability of Men Who Have Sex With Men Recruited From Venue-Time-Space Sampling and Facebook: A Cohort Study 
JMIR Research Protocols  2014;3(3):e37.
Background
Recruiting valid samples of men who have sex with men (MSM) is a key component of the US human immunodeficiency virus (HIV) surveillance and of research studies seeking to improve HIV prevention for MSM. Social media, such as Facebook, may present an opportunity to reach broad samples of MSM, but the extent to which those samples are comparable with men recruited from venue-based, time-space sampling (VBTS) is unknown.
Objective
The objective of this study was to assess the comparability of MSM recruited via VBTS and Facebook.
Methods
HIV-negative and HIV-positive black and white MSM were recruited from June 2010 to December 2012 using VBTS and Facebook in Atlanta, GA. We compared the self-reported venue attendance, demographic characteristics, sexual and risk behaviors, history of HIV-testing, and HIV and sexually transmitted infection (STI) prevalence between Facebook- and VTBS-recruited MSM overall and by race. Multivariate logistic and negative binomial models estimated age/race adjusted ratios. The Kaplan-Meier method was used to assess 24-month retention.
Results
We recruited 803 MSM, of whom 110 (34/110, 30.9% black MSM, 76/110, 69.1% white MSM) were recruited via Facebook and 693 (420/693, 60.6% black MSM, 273/693, 39.4% white MSM) were recruited through VTBS. Facebook recruits had high rates of venue attendance in the previous month (26/34, 77% among black and 71/76, 93% among white MSM; between-race P=.01). MSM recruited on Facebook were generally older, with significant age differences among black MSM (P=.02), but not white MSM (P=.14). In adjusted multivariate models, VBTS-recruited MSM had fewer total partners (risk ratio [RR]=0.78, 95% CI 0.64-0.95; P=.01) and unprotected anal intercourse (UAI) partners (RR=0.54, 95% CI 0.40-0.72; P<.001) in the previous 12 months. No significant differences were observed in HIV testing or HIV/STI prevalence. Retention to the 24-month visit varied from 81% for black and 70% for white MSM recruited via Facebook, to 77% for black and 78% for white MSM recruited at venues. There was no statistically significant differences in retention between the four groups (log-rank P=.64).
Conclusions
VBTS and Facebook recruitment methods yielded similar samples of MSM in terms of HIV-testing patterns, and prevalence of HIV/STI, with no differences in study retention. Most Facebook-recruited men also attended venues where VTBS recruitment was conducted. Surveillance and research studies may recruit via Facebook with little evidence of bias, relative to VBTS.
doi:10.2196/resprot.3342
PMCID: PMC4129125  PMID: 25048694
men who have sex with men, MSM; Facebook; venue-based time sampling; online MSM; social media recruitment of MSM
25.  An application of propensity score weighting to quantify the causal effect of rectal sexually transmitted infections on incident HIV among men who have sex with men 
Background
Exploring causal associations in HIV research requires careful consideration of numerous epidemiologic limitations. First, a primary cause of HIV, unprotected anal intercourse (UAI), is time-varying and, if it is also associated with an exposure of interest, may be on a confounding path. Second, HIV is a rare outcome, even in high-risk populations. Finally, for most causal, non-preventive exposures, a randomized trial is impossible. In order to address these limitations and provide a practical illustration of efficient statistical control via propensity-score weighting, we examine the causal association between rectal STI and HIV acquisition in the InvolveMENt study, a cohort of Atlanta-area men who have sex with men (MSM). We hypothesized that, after controlling for potentially confounding behavioral and demographic factors, the significant STI-HIV association would attenuate, but yield an estimate of the causal effect.
Methods
The exposure of interest was incident rectal gonorrhea or chlamydia infection; the outcome was incident HIV infection. To adjust for behavioral confounding, while accounting for limited HIV infections, we used an inverse probability of treatment weighted (IPTW) Cox proportional hazards (PH) model for incident HIV. Weights were derived from propensity score modeling of the probability of incident rectal STI as a function of potential confounders, including UAI in the interval of rectal STI acquisition/censoring.
Results
Of 556 HIV-negative MSM at baseline, 552 (99%) men were included in this analysis. 79 men were diagnosed with an incident rectal STI and 26 with HIV. 6 HIV-infected men were previously diagnosed with a rectal STI. In unadjusted analysis, incident rectal STI was significantly associated with subsequent incident HIV (HR (95%CI): 3.6 (1.4-9.2)). In the final weighted and adjusted model, the association was attenuated and more precise (HR (95% CI): 2.7 (1.2-6.4)).
Conclusions
We found that, controlling for time-varying risk behaviors and time-invariant demographic factors, diagnosis with HIV was significantly associated with prior diagnosis of rectal CT or GC. Our analysis lends support to the causal effect of incident rectal STI on HIV diagnosis and provides a framework for similar analyses of HIV incidence.
Electronic supplementary material
The online version of this article (doi:10.1186/s12874-015-0017-y) contains supplementary material, which is available to authorized users.
doi:10.1186/s12874-015-0017-y
PMCID: PMC4369368  PMID: 25888416
STI; HIV; Propensity scores; Survival analysis; Men who have sex with men; Marginal structural models

Results 1-25 (960789)