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1.  The relationship between age of coital debut and HIV seroprevalence among women in Durban, South Africa: a cohort study 
BMJ Open  2012;2(1):e000285.
Objectives
To investigate the impact of early sexual debut on HIV seroprevalence and incidence rates among a cohort of women.
Design
Prospective study.
Setting
KwaZulu-Natal, South Africa.
Participants
A total of 3492 sexually active women who consented to screen a HIV prevention trial during September 2002 to September 2005; a total of 1485 of them were followed for approximately 24 months.
Primary and secondary outcome measures
HIV seroprevalence among those who were screened for the trial and HIV seroconversion among those who seroconverted during the study.
Results
Lowest quintiles of age at sexual debut, less than high school education, a higher number of lifetime sexual partners and lack of cohabitation, being diagnosed as having herpes simplex virus 2 and other sexually transmitted infections were all significantly associated with prevalent HIV infection in multivariate analysis. During follow-up, 148 (6.8 per 100 person-years, 95% CI 5.8 to 8.0) women seroconverted. Highest seroconversion rate was observed among women who had reported to have had sex 15 years or younger (12.0 per 100 person-years, 95% CI 8.0 to 18.0). Overall, impact of risk factors considered in this study was associated with considerable potential reductions in HIV prevalence and incidence rates (population attributable risk: 85%, 95% CI 84% to 87% and population attributable risk: 77%, 95% CI 72% to 82%, respectively).
Conclusions
The association of HIV status with younger age at sexual debut may likely due to an increased number of lifetime partners. This increase could result from longer duration of sexual life. Prevention of HIV infection should include efforts to delay age at first sex in young women.
Trial registration number
NCT00121459.
Article summary
Article focus
Early sexual debut may increase women's vulnerability to HIV infection.
Early sexual debut has been associated with increased sexual risk-taking behaviour, such as having multiple partners.
Delaying sexual debut may have been one of the key changes in behaviour, which lead to a decline in HIV infection in the past.
Key messages
Our results showed that women who initiated sexual activity early were more likely to engage in risky sexual behaviours.
A clear trend observed indicating that early onset sexual activity was associated with increased HIV seroprevalence and incidence.
Comprehensive sexual education programmes should reach out-of-school youth, who may be at heightened vulnerability, should be identified as well.
Strengths and limitations of this study
We cannot rule out the effects of unmeasured characteristics such as multiple or concurrent sex partners and commercial sex on our findings. No data concerning migration, socioeconomic status at the time of sexual debut or sexual behaviour data from male partners.
Nevertheless, current study used the data from the region where the HIV epidemic is severely high among particularly young women.
doi:10.1136/bmjopen-2011-000285
PMCID: PMC3253418  PMID: 22223838
2.  Developing and validating a scoring tool for identifying people who inject drugs at increased risk of hepatitis C virus infection 
BMJ Open  2012;2(1):e000387.
Objectives
To develop and validate a scoring tool based on demographic and injecting risk behaviours to identify those who require additional, non-routine serological screening for hepatitis C virus (HCV) by assessing their personal risk.
Design
Cross-sectional and prospective cohorts.
Setting
People who inject drugs (PWID) and attended Needle and Syringe Programs (NSP) in Australia during the period from 1998 to 2008.
Participants
Cross-sectional data included 16 127 PWID who attended NSP in Australia. Prospective data included 215 HCV-negative PWID who were recruited through street-based outreach, methadone clinics in Australia.
Primary and secondary outcome measures
HCV seroprevalence in the cross-sectional and HCV seroconversions in the prospective data sets.
Results
Current study included 16 127 PWID who attended NSP in Australia. Type of drug last injected, frequency and duration of injecting, sharing needles and syringes or other injecting equipment and imprisonment history were associated with HCV infection in all age groups. Strong relationships between an individual's ‘HCV score’ and their risk of testing HCV antibody positive were observed. An estimated 78% (95% CI 75% to 81%), 82% (95% CI 80% to 84%), 80% (95% CI 78% to 82%) and 80% (95% CI 77% to 82%) of HCV infections across the age groups (<25, 25–29, 30–39 and ≥40 years) would be avoided if participants in the upper four quintiles of HCV scores fell instead into the lowest quintile.
Conclusions
Knowledge of HCV status has important implications for public health and care and treatment. Risk assessment strategies may assist in alerting PWID who are at increased risk of HCV infection to present for testing.
Article summary
Article focus
Although the risk factors for incident infection are well established, the literature suggests that a number of barriers may prevent PWID presenting for screening.
Study developed a scoring tool based on demographic and injecting risk behaviours to identify those who require additional, non-routine serological screening for HCV by assessing their personal risk.
Key messages
Current clinical practice guidelines recommend HCV screening of individuals with a history of injecting drugs.
However, this recommendation focuses on a single risk factor (ie, injecting drug use), whereas considering the cumulative effect of multiple risk factors among PWID can more precisely identify people in need of additional non-routine screening.
Strengths and limitations of this study
Our prediction equation is based on 11 years of data and >16 000 participants. Ideal risk assessment methods or prediction models should be derived from large representative samples.
The study population is limited to those who participated in the Australian Needle and Syringe Program Survey, which may result in selection bias.
We were not able to differentiate between acute, recent and chronic infections.
doi:10.1136/bmjopen-2011-000387
PMCID: PMC3253425  PMID: 22218720
3.  Population attributable risk for chlamydia infection in a cohort of young international travellers (backpackers) and residents in Australia 
BMJ Open  2011;1(1):e000004.
Aim
To estimate the population attributable risk (PAR) for Chlamydia trachomatis infection in young men and women in Sydney, Australia.
Method
Multivariate logistic regression was used to examine the association between demographic, sexual behaviour and other potential risk factors and chlamydia positivity in young (≤30 years) heterosexual international travellers (backpackers) and Australian residents attending a sexual health clinic. Point and interval estimates of PAR were calculated to quantify the proportion of chlamydia infections that can theoretically be prevented if a combination of risk factors is eliminated from a target population.
Results
In males, the PAR associated with inconsistent condom use in the past 3 months was 65% (95% CI 56% to 71%) in backpackers compared to 50% (95% CI 41% to 56%) in non-backpackers and the PAR associated with reporting three or more female sexual partners in the past 3 months was similar between male backpackers and non-backpackers (33% (95% CI 28% to 40%) and 36% (95% CI 32% to 41%), respectively). In females, the PAR associated with inconsistent condom use in the past 3 months was 51% (95% CI 42% to 59%) in backpackers compared to 41% (95% CI 31% to 51%) in non-backpackers, and the PAR associated with reporting three or more male sexual partners in the past 3 months was 14% (95% CI 11% to 18%) in backpackers compared to 30% (95% CI 25% to 37%) in non-backpackers.
Conclusion
These findings suggest that the largest number of chlamydia infections could be avoided by increasing condom use, particularly in backpackers. Reporting multiple partners was also associated with a large proportion of infections and the risk associated with this behaviour should be considered in health promotion strategies.
Article summary
Article focus
Risk factors for chlamydia infection were determined among young, heterosexual backpackers and Australian residents.
A novel statistical methodology was used to investigate the potential impact of eliminating risk factors on chlamydia infection at a population level.
Key messages
Results suggest that the majority of the chlamydia infections could be avoided by increased condom use, particularly among backpackers.
Multiple sex partners in past 3 months was also associated with a high proportion of chlamydia infections at the population level.
Strengths and limitations of this study
This is the first study to investigate the potential impact of sexual risk behaviours for chlamydia infection at the population level.
The study population was sexual health clinic attendees who are likely to be at higher risk for chlamydia infection compared to the general population.
doi:10.1136/bmjopen-2010-000004
PMCID: PMC3191383  PMID: 22021720
Hepatitis C; HIV; HIV testing; homosexuality; infectious disease
4.  Developing and validating a risk scoring tool for chlamydia infection among sexual health clinic attendees in Australia: a simple algorithm to identify those at high risk of chlamydia infection 
BMJ Open  2011;1(1):e000005.
Objective
To develop and validate a risk scoring tool to identify those who are at increased risk of chlamydia infection.
Methods
We used demographic data, sexual behaviour information and chlamydia positivity results from more than 45 000 individuals who attended Sydney Sexual Health Centre between 1998 and 2009. Participants were randomly allocated to either the development or internal validation data set. Using logistic regression, we created a prediction model and weighted scoring system using the development data set and calculated the odds ratio of chlamydia positivity for participants in successively higher quintiles of score. The internal validation data set was used to evaluate the performance characteristics of the model for five quintiles of risk scores including population attributable risk, sensitivity and specificity.
Results
In the prediction model, inconsistent condom use, increased number of sexual partners in last 3 months, genital or anal symptoms and presenting to the clinic for sexually transmitted infections screening or being a contact of a sexually transmitted infection case were consistently associated with increased risk of chlamydia positivity in all groups. High scores (upper quintiles) were significantly associated with increased risk of chlamydia infection. A cut-point score of 20 or higher distinguished a increased risk group with a sensitivity of 95%, 67% and 79% among heterosexual men, women and men who have sex with men (MSM), respectively.
Conclusion
The scoring tool may be included as part of a health promotion and/or clinic website to prompt those who are at increased risk of chlamydia infection, which may potentially lead to increased uptake and frequency of testing.
Article summary
Article focus
The authors created a risk assessment tool that allows people to estimate their own chlamydia risk score based on simple non-invasive variables.
Key messages
The tool described here will potentially provide a simple and cost-effective method of identifying and alerting individuals who would benefit from chlamydia screening.
This tool may be included as part of a health promotion and/or clinic website.
This tool may potentially lead to increased uptake and frequency of testing.
Strengths and Limitations
This is the first study to utilize statistical methods to derive a locally-specific assessment tool using 12 years of data from more than 45 000 men and women.
The Study population was sexual health clinic attendees who are likely to be at higher risk for Chlamydia infection compared to the general population.
doi:10.1136/bmjopen-2010-000005
PMCID: PMC3191384  PMID: 22021721
Chlamydia infection; risk prediction; hepatitis C; HIV; HIV testing; homosexuality; infectious disease; epidemiology; sexual medicine; health informatics

Results 1-4 (4)