The HIV care continuum is a critical framework for situational awareness of the HIV epidemic, yet challenges to accurate enumeration of continuum components hamper continuum estimation in practice. We describe local, surveillance-based estimation of the HIV continuum in the United States, reviewing common practices as recommended by the Centers for Disease Control and Prevention. Furthermore, we review some challenges and biases likely to threaten existing continuum estimates. Current estimates rely heavily on the use of CD4 cell count and HIV viral load laboratory results reported to surveillance programs as a proxy for receipt of HIV-related outpatient care. As such, continuum estimates are susceptible to bias due to incomplete laboratory reporting and imperfect sensitivity and specificity of laboratory tests as a proxy for routine HIV care. Migration of HIV-infected persons between jurisdictions also threatens the validity of continuum estimates. Data triangulation may improve but not fully alleviate biases.
HIV Cascade; Treatment as Prevention
The impact of routine, opt-out HIV testing programs in clinical settings is inconclusive. The objective of this study was to estimate the impact of an expanded, routine HIV testing program in North Carolina sexually transmitted disease (STD) clinics on HIV testing and case detection.
Adults aged 18–64 who received an HIV test in a North Carolina STD clinic July 1, 2005 through June 30, 2011 were included in this analysis, dichotomized at the date of implementation on November 1, 2007. HIV testing and case detection counts and rates were analyzed using interrupted time series analysis, and Poisson and multilevel logistic regression.
Pre-intervention, 426 new HIV-infected cases were identified from 128,029 tests (0.33%), whereas 816 new HIV-infected cases were found from 274,745 tests post-intervention (0.30%). Pre-intervention, HIV testing increased by 55 tests per month (95% confidence interval [CI]: 41, 72), but only 34 tests per month (95% CI: 26, 42) post-intervention. Increases in HIV testing rates were most pronounced in females and non-Hispanic whites. A slight pre-intervention decline in case detection was mitigated by the intervention (mean difference [MD]=0.01; 95% CI: −0.02, 0.05). Increases in case detection rates were observed among females and non-Hispanic blacks.
The impact of a routine HIV screening in North Carolina STD clinics was marginal, with the greatest benefit among persons not traditionally targeted for HIV testing. The use of a pre-intervention comparison period identified important temporal trends that otherwise would have been ignored.
routine HIV testing; STD clinic; intervention analysis
During cluster investigation, index patients name social contacts that are not sex or drug-sharing partners. The likelihood of identifying new HIV infections among social contacts is unknown. We hypothesized greater odds of identifying new infections among social contacts identified by men who report sex with men (MSM). We reviewed North Carolina HIV diagnoses during 2002–2005 and used logistic regression to compare testing results among social contacts of MSM, men who report sex with women only (MSW) and women. HIV was newly diagnosed among 54/601 (9.0%) social contacts tested named by MSM, 16/522 (3.1%) named by MSW, and 23/639 (3.6%) named by women. Compared with those named by MSW, odds of new HIV diagnosis were greater among MSM social contacts (adjusted odds ratio: 2.5; 95% confidence interval: 1.3–4.7). Testing social contacts identified previously undiagnosed HIV infections and could provide an opportunity to interrupt transmission.
contact tracing; HIV infections; prevention & control; male; sexual behavior
In a largely rural region of North Carolina during 1998–2002, outbreaks occurred of heterosexually-transmitted syphilis, tied to crack cocaine use and exchange of sex for drugs and money. Sexual partnership mixing patterns are an important characteristic of sexual networks that relate to transmission dynamics of STIs.
Using contact tracing data collected by Disease Intervention Specialists, we estimated Newman assortativity coefficients and compared values in counties experiencing syphilis outbreaks to non-outbreak counties, with respect to race/ethnicity, race/ethnicity and age, and the cases' number of social/sexual contacts, infected contacts, sex partners, and infected sex partners, and syphilis disease stage (primary, secondary, early latent).
Individuals in the outbreak counties had more contacts and mixing by the number of sex partners was disassortative in outbreak counties and assortative non-outbreak counties. Whereas mixing by syphilis disease stage was minimally assortative in outbreak counties, it was disassortative in non-outbreak areas. Partnerships were relatively discordant by age, especially among older White men, who often chose considerably younger female partners.
Whether assortative mixing exacerbates or attenuates the reach of STIs into different populations depends on the characteristic/attribute and epidemiologic phase. Examination of sexual partnership characteristics and mixing patterns offers insights into the growth of STI outbreaks that complement other research methods.
sexual networks; syphilis; heterosexual transmission; mixing patterns
Describe and quantify differences among the year of first positive HIV test from patient report, the medical record, and HIV/AIDS surveillance data.
We merged two clinic-based studies with overlapping HIV-infected participant populations in North Carolina with the HIV/AIDS Reporting System (HARS) and examined the first positive HIV test year from patient report, the medical record, and HARS. Matches were considered the same year of diagnosis.
The self-reported year of diagnosis had high agreement with the medical record (67% matched exactly and 19% differed by one year, weighted kappa=0.85), although there were wide 95% limits of agreement (−4.0 earlier to 3.9 years later). On average, the dates of diagnosis from patient report and the medical record were earlier than HARS with wide 95% limits of agreement (7.5 years earlier to 6.0 years later for patient report vs. HARS, 7.7 years earlier to 6.0 years later for medical record vs. HARS).
These measures could not reliably be used interchangeably as there was wide variability in both directions. Although collection of data from patient report or existing sources is convenient, cost-effective, and efficient, there is significant variability between sources.
HIV infections; reproducibility of results; HIV serodiagnosis; surveillance; comparative study
HIV transmission is influenced by status awareness and receipt of care and treatment. We analyzed these attributes of named partners of persons with acute HIV infection (index AHI cases) to characterize the transmission landscape in North Carolina (NC).
Secondary analysis of programmatic data.
We used data from the NC Screening and Tracing of Active Transmission Program (2002–2013) to determine HIV status (uninfected, AHI, or chronic HIV infection [CHI]), diagnosis status (new or previously-diagnosed), and care and treatment status (not in care, in care and not on treatment, in care and on treatment) of index AHI cases' named partners. We developed an algorithm identifying the most likely transmission source among known HIV-infected partners to estimate the proportion of transmissions arising from contact with persons at different HIV continuum stages. We conducted a complementary analysis among a subset of index AHI cases and partners with phylogenetically-linked viruses.
Overall, 358 index AHI cases named 932 partners, of which 218 were found to be HIV-infected (162 (74.3%) previously-diagnosed, 11 (5.0%) new AHI, 45 (20.6%) new CHI). Most transmission events appeared attributable to previously-diagnosed partners (77.4%, 95% confidence interval 69.4–85.3%). Among these previously-diagnosed partners, 23.2% (14.0–32.3%) were reported as in care and on treatment near the index AHI case diagnosis date. In the subset study of 33 phylogenetically-linked cases and partners, 60.6% of partners were previously diagnosed (43.9–77.3%).
A substantial proportion of HIV transmission in this setting appears attributable to contact with previously-diagnosed partners, reinforcing the need for improved engagement in care after diagnosis.
Thirty percent of tuberculosis (TB) patients in New York City in 2007 were not tested for HIV, which may be attributable to differential testing behaviors between private and public TB providers. Adult TB cases in New York City from 2001–2007 (n=5172) were evaluated for an association between TB provider type (private or public) and HIV testing. Outcomes examined were offers of HIV tests and patient refusal of HIV testing, using multivariate logistic and binomial regression, respectively. HIV test offers were less frequent among patients who visited only private providers than patients who visited only public providers (males: adjusted odds ratio [aOR]=0.33, 95% confidence interval (CI): 0.15–0.74; females: aOR=0.26, 95% CI: 0.12–0.57). Changing from private to public providers was associated with an increase in HIV tests offered among male patients (aOR=1.96, 95% CI: 1.04–3.70). Among patients who did not use substances, those who visited only private providers were more likely to refuse HIV testing than those who visited only public providers (males: adjusted prevalence ratio [aPR]=1.26, 95% CI: 0.99–1.60; females: aPR=1.78, 95% CI: 1.43–2.22). Patients of private providers were less likely to have an HIV test performed during their TB treatment. Education of TB providers should emphasize HIV testing of all TB patients, especially among patients who are traditionally considered low-risk.
HIV testing; tuberculosis; medical providers
North Carolina locates acute HIV cases by pooled nucleic acid testing of HIV- antibody negative serum samples. Here, 224 pools of 80 HIV-negative samples (N=17,920) were screened for viral RNA from HCV, GBV-C, and influenza A. No evidence of influenza A was found, but HCV and GBV-C were common (1.2% and 1.7% prevalence, respectively), demonstrating the utility of pooled testing in locating individuals that may remain undiagnosed otherwise. By sequencing positive pools, potential transmission clusters may be located as well.
Hepatitis C Virus; GB Virus C; Influenza A; Public Health; Emerging Pathogens; Acute HIV Infection
We evaluated emergency department (ED) provider adherence to guidelines for concurrent HIV-sexually transmitted disease (STD) testing within an expanded HIV testing program and assessed demographic and clinical factors associated with concurrent HIV-STD testing.
We examined concurrent HIV-STD testing in a suburban academic ED with a targeted, expanded HIV testing program. Patients aged 18–64 years who were tested for syphilis, gonorrhea, or chlamydia in 2009 were evaluated for concurrent HIV testing. We analyzed demographic and clinical factors associated with concurrent HIV-STD testing using multivariate logistic regression with a robust variance estimator or, where applicable, exact logistic regression.
Only 28.3% of patients tested for syphilis, 3.8% tested for gonorrhea, and 3.8% tested for chlamydia were concurrently tested for HIV during an ED visit. Concurrent HIV-syphilis testing was more likely among younger patients aged 25–34 years (adjusted odds ratio [AOR] = 0.36, 95% confidence interval [CI] 0.78, 2.10) and patients with STD-related chief complaints at triage (AOR=11.47, 95% CI 5.49, 25.06). Concurrent HIV-gonorrhea/chlamydia testing was more likely among men (gonorrhea: AOR=3.98, 95% CI 2.25, 7.02; chlamydia: AOR=3.25, 95% CI 1.80, 5.86) and less likely among patients with STD-related chief complaints at triage (gonorrhea: AOR=0.31, 95% CI 0.13, 0.82; chlamydia: AOR=0.21, 95% CI 0.09, 0.50).
Concurrent HIV-STD testing in an academic ED remains low. Systematic interventions that remove the decision-making burden of ordering an HIV test from providers may increase HIV testing in this high-risk population of suspected STD patients.
Combating the syndemics of tuberculosis (TB) and HIV in the United States will require increasing efficiency as the incidence of TB declines. Fortunately, new tools such as the interferon gamma release assays can be combined with existing strategies such as opt-out HIV testing to facilitate simultaneous, integrated testing for both infections. We describe the lessons learned from our experience with integrated testing for TB and HIV in the setting of TB contact investigations in North Carolina. Integrated testing represents a unique opportunity to leverage TB and HIV program resources to enhance case detection and improve linkages to care. However, joint training in field investigations and diagnostics is critical prior to conducting contact investigations. Furthermore, integrated testing must be tightly coupled to treatment and prevention programs to reduce disease transmission and morbidity from untreated disease in communities.
Sexually transmitted infections (STIs) spread along sexual networks whose structural characteristics promote transmission that routine surveillance may not capture. Cases who have partners from multiple localities may operate as spatial network bridges, thereby facilitating geographical dissemination. We investigated the relationships between surveillance, sexual networks, and spatial bridges for syphilis outbreaks in rural counties of North Carolina.
We selected from the state health department’s surveillance database cases diagnosed with primary, secondary, or early latent syphilis during October 1998 - December 2002 residing in central and southeastern North Carolina, along with their sex partners, and their social contacts irrespective of infection status. We applied matching algorithms to eliminate duplicate names and create a unique roster of partnerships from which networks were compiled and graphed. Network members were differentiated by disease status and county of residence.
In the county most affected by the outbreak, densely connected networks indicative of STI outbreaks were consistent with elevated incidence and a large case load. In other counties, the case loads were low with fluctuating incidence, but network structures suggested the presence of outbreaks. In a county with stable, low incidence and a high number of cases, the networks were sparse and dendritic, indicative of endemic spread. Outbreak counties exhibited densely connected networks within well-defined geographic boundaries and low connectivity between counties; spatial bridges did not seem to facilitate transmission.
Simple visualization of sexual networks can provide key information to identify communities most in need of resources for outbreak investigation and disease control.
Persistent nontreponemal titers after treatment are common among patients with early syphilis. We retreated 82 human immunodeficiency virus–negative early syphilis participants who were serofast at 6 months using benzathine penicillin. Only 27% exhibited serological response after retreatment and after an additional 6 months of follow-up.
syphilis; serofast; retreatment; serological response
HIV infections increased 48% among young, Black men who have sex with men (MSM) in the United States between 2006–2009. Incomplete understanding of this trend undermines prevention strategy development. We investigated a sexual network to characterize the risk environment in which young, Black MSM acquire HIV.
Persons reported to the state following diagnosis of HIV or syphilis were included, along with sexual partners. We used network mapping alongside descriptive and bivariate statistics to characterize network connections. Generalized linear models assessed predictors of having untraceable sex partners.
The network included 398 individuals and 419 sexual relationships. Three-quarters were Black (n=299); 92% were MSM. Median age at first network appearance was 26 years and decreased over time (P<0.001). HIV prevalence was at least 29% (n=117); serostatus was unknown for 47% of the network, either because they were untraceable (n=150) or refused HIV testing (n=39). One in 5 network members diagnosed with HIV had a subsequent incident sexually transmitted infection. In multivariable models, one-time encounters increased the risk of having an untraceable partner (risk ratio 4.51, 95% CI, 2.27, 8.97), while being acutely HIV infected at diagnosis reduced it (RR 0.27, 95% CI, 0.08, 0.89).
HIV prevalence in this sexual network of young, Black MSM rivals that of sub-Saharan Africa, reflecting dramatically increased risk of acquiring HIV from the moment one entered the network. Prevention efforts for this population must consider the effect of sexual networks on HIV risk, and find ways of leveraging network structure to reduce transmission.
HIV; African-American; men who have sex with men; sexual networks
Hormonal contraception use by women may increase the risk of acquiring certain sexually transmitted infections. We explored the effect of hormonal contraceptive use, specifically oral contraception (OC), and depot-medroxyprogesterone acetate (DMPA) on Trichomonas vaginalis infections in women.
We examined data from a prospective case–control study of women with trichomoniasis and noninfected female patients recruited from 3 public sexually transmitted disease clinics. Women with positive wet mount microscopy or T. vaginalis culture results were classified as having trichomoniasis. Participants underwent physical examinations, sexually transmitted infections testing and completed questionnaires which included information about demographics, sexual behavior, douching and contraceptive use. We assessed the association between hormonal contraceptives and trichomoniasis using bivariable and multivariable analysis and estimated exposure odds ratios (ORs) and adjusted odds ratios (aORs) with 95% confidence intervals (CIs).
We identified 427 women with trichomoniasis and 144 uninfected women who had information reported about contraception use. Compared with nonhormonal contraceptive use, OC use was negatively associated with trichomoniasis in bivariable analysis (OR: 0.5; 95% CI: 0.3–0.8). This association was no longer statistically significant after adjusting for demographic variables, douching and condom use (aOR: 0.9; 95% CI: 0.5–1.6). Use of DMPA, compared with nonhormonal contraceptive use, was not associated with trichomoniasis in bivariable or multivariable analyses (OR: 1.0, 95% CI: 0.5–2.1; aOR = 1.4, 95% CI: 0.6–3.4, respectively).
Although OC use appeared to have a protective effect in the bivariable analysis, the hormonal contraceptives OC and DMPA were not associated with T. vaginalis infection after adjustment for other factors.
Serologic tests for syphilis (STS) results at time of diagnosis are the basis for evaluating response to syphilis therapy. Following treatment, however, STS titers may continue to increase for several weeks. We evaluated RPR titer variation over the 14 days following therapy using data from a recent large, prospective RCT.
Prospectively enrolled participants in North America and Madagascar with primary, secondary or early latent syphilis were randomly assigned to penicillin, doxycycline (in the case of penicillin allergy) or azithromycin treatment. Blood for RPR analysis was drawn at days 0, 7, and 14 post-treatment. All RPR titers were determined simultaneously at a central laboratory.
470 patients had data available for at least 2 of 3 RPR measurements. Overall, 20% of patients showed a titer increase of at least one dilution in the 14 days following therapy. The greatest proportion of titer increases following therapy was seen in patients with primary syphilis. Comparing outcome of therapy using the initial (day 0) RPR titer vs. the maximal RPR titer (over 14 days), resulted in outcome reclassification in 2.98% of participants.
Despite the fact that about 20% of early syphilis patients had increases in RPR titers immediately following treatment, these changes rarely influenced assessment of therapeutic outcome. Only 3% of patients treated would have been reclassified.
Syphilis testing; RPR; Syphilis Treatment Outcome
Disease Intervention Specialists (DIS) in North Carolina (NC) have less time to conduct partner notification due to competing responsibilities while simultaneously facing increased case loads due to increased HIV testing. We developed a model to predict undiagnosed HIV infection in sexual partners to prioritize DIS interviews.
We abstracted demographic, behavioral, and partnership data from DIS records of HIV-infected persons reported in two NC surveillance regions between January 1, 2003 and December 31, 2007. Multiple logistic regression with generalized estimating equations was used to develop a predictive model and risk scores among newly diagnosed persons and their partners. Sensitivities and specificities of the risk scores at different cutoffs were used to examine algorithm performance.
Five factors predicted a partnership between a person with newly diagnosed HIV infection and an undiagnosed partner—four weeks or fewer between HIV diagnosis and DIS interview, no history of crack use, no anonymous sex, fewer total sexual partners reported to DIS, and sexual partnerships between an older index case and younger partner. Using this model, DIS could choose an appropriate cutoff for locating a particular partner by determining the weight of false negatives relative to false positives.
While the overall predictive power of the model is low, it is possible to reduce the number of partners that need to be located and interviewed while maintaining high sensitivity. If DIS continue to pursue all partners, the model would be useful in identifying partners in which to invest more resources for locating.
HIV; partner notification; modeling; decision
Many adults in the United States enter primary care late in the course of HIV infection, countering the clinical benefits of timely HIV services and missing opportunities for risk reduction. Our objective was to determine if perceived social support was associated with delay entering care after an HIV diagnosis. Two hundred sixteen patients receiving primary care at a large, university-based HIV outpatient clinic in North Carolina were included in the study. Dimensions of functional social support (emotional/informational, tangible, affectionate and positive social interaction) were quantified with a modified Medical Outcomes Study Social Support Scale and included in proportional hazard models to determine their effect on delays seeking care. The median delay between diagnosis and entry to primary care was 5.9 months. Levels of social support were high but only positive social interaction was moderately associated with delayed presentation in adjusted models. The effect of low perceived positive social interaction on the time to initiation of primary care differed by history of alcoholism (no history of alcoholism, hazard ratio (HR): 1.43, 95% confidence interval (CI): 0.88, 2.34; history of alcoholism, HR: 0.71, 95% CI: 0.40, 1.28). Ensuring timely access to HIV care remains a challenge in the southeastern United States. Affectionate, tangible, and emotional/informational social support were not associated with the time from diagnosis to care. The presence of positive social interaction may be an important factor influencing care seeking behavior after diagnosis.
HIV infection; social support; time factors; delivery of health care; southeastern United States
A substantial proportion of patients treated for early syphilis have serofast nontreponemal titers after therapy. Serological cure at 6 months is associated with age, number of sexual partners, Jarisch-Herxheimer reaction, and an interaction between syphilis stage and baseline nontreponemal titers.
Background. Syphilis management requires serological monitoring after therapy. We compared factors associated with serological response after treatment of early (ie, primary, secondary, or early latent) syphilis.
Methods. We performed secondary analyses of data from a prospective, randomized syphilis trial conducted in the United States and Madagascar. Human immunodeficiency virus (HIV)–negative participants aged ≥18 years with early syphilis were enrolled from 2000–2009. Serological testing was performed at baseline and at 3 and 6 months after treatment. At 6 months, serological cure was defined as a negative rapid plasma reagin (RPR) test or a ≥4-fold decreased titer, and serofast status was defined as a ≤2-fold decreased titer or persistent titers that did not meet criteria for treatment failure.
Results. Data were available from 465 participants, of whom 369 (79%) achieved serological cure and 96 (21%) were serofast. In bivariate analysis, serological cure was associated with younger age, fewer sex partners, higher baseline RPR titers, and earlier syphilis stage (P ≤ .008). There was a less significant association with Jarisch-Herxheimer reaction after treatment (P = .08). Multivariate analysis revealed interactions between log-transformed baseline titer with syphilis stage, in which the likelihood of cure was associated with increased titers among participants with primary syphilis (adjusted odds ratio [AOR] for 1 unit change in log2 titer, 1.83; 95% confidence interval [CI], 1.25–2.70), secondary syphilis (AOR, 3.15; 95% CI, 2.14–4.65), and early latent syphilis (AOR, 1.86; 95% CI, 1.44–2.40).
Conclusions. Serological cure at 6 months after early syphilis treatment is associated with age, number of sex partners, Jarisch-Herxheimer reaction, and an interaction between syphilis stage and baseline RPR titer.
Persons with unrecognized HIV infection forgo timely clinical intervention and may unknowingly transmit HIV to partners. However, in the United States, unrecognized infection and late diagnosis are common. To understand barriers and facilitators to HIV testing and care, we conducted a qualitative study of 24 HIV infected persons attending a Southeastern HIV clinic who presented with clinically advanced illness. The primary barrier to HIV testing prior to diagnosis was perception of risk; consequently, most participants were diagnosed after the onset of clinical symptoms. While most patients were anxious to initiate care rapidly after diagnosis, some felt frustrated by the passive process of connecting to specialty care. The first visit with an HIV care provider was identified as critical in the coping process for many patients. Implications for the implementation of recent CDC HIV routine screening guidelines are discussed.
HIV Infection; Voluntary Counseling and Testing; Delivery of Health Care; Southeastern United States; Social Support
Herpes labialis is a common skin infective condition, worldwide, which is primarily caused by HSV-1. Recurrent episodes of herpes labialis, also known as cold sores, can be frequent, painful, long-lasting and disfiguring for infected patients. At present, there are two types of antivirals for the treatment of herpes labialis, topical and oral, which are available over the counter or as prescription-only. The aim of antiviral therapy is to block viral replication to enable shortening the duration of symptoms and to accelerate healing of the lesions associated with herpes labialis. This review examines the evidence for the effectiveness of current topical and oral antivirals in the management of recurrent episodes of herpes labialis. In most countries, oral antivirals for herpes labialis are available as prescription-only. However, in early 2010, the oral antiviral famciclovir was reclassified from prescription-only medicine to pharmacist-controlled status in New Zealand. The benefits and risks associated with moving an antiviral therapy for herpes labialis from prescription-only to pharmacist-controlled status are reviewed here, and the implications for patients, general physicians and pharmacists are considered.
Herpes labialis; Coldsores; Famciclovir; Aciclovir; Valaciclovir; HSV-1
Two previous studies of a herpes simplex virus type 2 (HSV-2) subunit vaccine containing glycoprotein D in HSV-discordant couples revealed 73% and 74% efficacy against genital disease in women who were negative for both HSV type 1 (HSV-1) and HSV-2 antibodies. Efficacy was not observed in men or HSV-1 seropositive women.
We conducted a randomized, double-blind efficacy field trial involving 8323 women 18 to 30 years of age who were negative for antibodies to HSV-1 and HSV-2. At months 0, 1, and 6, some subjects received the investigational vaccine, consisting of 20 μg of glycoprotein D from HSV-2 with alum and 3-O-deacylated monophosphoryl lipid A as an adjuvant; control subjects received the hepatitis A vaccine, at a dose of 720 enzyme-linked immunosorbent assay (ELISA) units. The primary end point was occurrence of genital herpes disease due to either HSV-1 or HSV-2 from month 2 (1 month after dose 2) through month 20.
The HSV vaccine was associated with an increased risk of local reactions as compared with the control vaccine, and it elicited ELISA and neutralizing antibodies to HSV-2. Overall, the vaccine was not efficacious; vaccine efficacy was 20% (95% confidence interval [CI], −29 to 50) against genital herpes disease. However, efficacy against HSV-1 genital disease was 58% (95% CI, 12 to 80). Vaccine efficacy against HSV-1 infection (with or without disease) was 35% (95% CI, 13 to 52), but efficacy against HSV-2 infection was not observed (−8%; 95% CI, −59 to 26).
In a study population that was representative of the general population of HSV-1– and HSV-2–seronegative women, the investigational vaccine was effective in preventing HSV-1 genital disease and infection but not in preventing HSV-2 disease or infection. (Funded by the National Institute of Allergy and Infectious Diseases and GlaxoSmithKline; ClinicalTrials.gov number, NCT00057330.)
A major challenge in mapping health data is protecting patient privacy while maintaining the spatial resolution necessary for spatial surveillance and outbreak identification. A new adaptive geomasking technique, referred to as the donut method, extends current methods of random displacement by ensuring a user-defined minimum level of geoprivacy. In donut method geomasking, each geocoded address is relocated in a random direction by at least a minimum distance, but less than a maximum distance. The authors compared the donut method with current methods of random perturbation and aggregation regarding measures of privacy protection and cluster detection performance by masking multiple disease field simulations under a range of parameters. Both the donut method and random perturbation performed better than aggregation in cluster detection measures. The performance of the donut method in geoprivacy measures was at least 42.7% higher and in cluster detection measures was less than 4.8% lower than that of random perturbation. Results show that the donut method provides a consistently higher level of privacy protection with a minimal decrease in cluster detection performance, especially in areas where the risk to individual geoprivacy is greatest.
cluster analysis; confidentiality; demography; epidemiologic methods; population surveillance; public health practice
Geomasking is used to provide privacy protection for individual address information while maintaining spatial resolution for mapping purposes. Donut geomasking and other random perturbation geomasking algorithms rely on the assumption of a homogeneously distributed population to calculate displacement distances, leading to possible under-protection of individuals when this condition is not met. Using household data from 2007, we evaluated the performance of donut geomasking in Orange County, North Carolina. We calculated the estimated k-anonymity for every household based on the assumption of uniform household distribution. We then determined the actual k-anonymity by revealing household locations contained in the county E911 database. Census block groups in mixed-use areas with high population distribution heterogeneity were the most likely to have privacy protection below selected criteria. For heterogeneous populations, we suggest tripling the minimum displacement area in the donut to protect privacy with a less than 1% error rate.
donut geomasking; confidentiality; k-anonymity; privacy protection; spatial resolution
Patients who participate in clinical trials may experience better clinical outcomes than patients who initiate similar therapy within clinical care (trial effect), but no published studies have evaluated a trial effect in HIV clinical trials.
To examine a trial effect we compared virologic suppression (VS) among patients who initiated HAART in a clinical trial versus in routine clinical care. VS was defined as a plasma HIV RNA ≤400 copies/ml at six months after HAART initiation and was assessed within strata of early (1996–99) or current (2000–06) HAART periods. Risk ratios (RR) were estimated using binomial models.
Of 738 persons initiating HAART, 30.6% were women, 61.7% were black, 30% initiated therapy in a clinical trial and 67% (n = 496) had an evaluable six month HIV RNA result. HAART regimens differed between the early and current periods (p<0.001); unboosted PI regimens (55.6%) were more common in the early and NNRTI regimens (46.4%) were more common in the current period. Overall, 78% (95%CI 74, 82%) of patients achieved VS and trial participants were 16% more likely to achieve VS (unadjusted RR 1.16, 95%CI 1.06, 1.27). Comparing trial to non-trial participants, VS differed by study period. In the early period, trial participants initiating HAART were significantly more likely to achieve VS than non-trial participants (adjusted RR 1.33; 95%CI 1.15, 1.54), but not in the current period (adjusted RR 0.98; 95%CI 0.87, 1.11).
A clear clinical trial effect on suppression of HIV replication was observed in the early HAART period but not in the current period.