Overlooked Threats to Respondent Driven Sampling Estimators: Peer Recruitment Reality, Degree Measures, and Random Selection Assumption

Not Getting to Zero HIV Infections Among People Who Inject Drugs in San Francisco, California

We analyzed data from San Francisco's National HIV Behavioral Surveillance for 2018 and 2022 to assess progress towards getting to zero HIV infections among people who inject drugs (PWID). HIV prevalence showed little change from 2018 (10.9%) to 2022 (11.4%). UNAIDS 90-90-90 targets were not met during the four-year interval, accompanied by a drop in HIV testing in the last year (from 73.5 to 43.4%, X2(1) = 82.76, p < 0.001). We found no evidence that the HIV epidemic is heading towards zero among PWID. Our data are a wakeup call to revitalize our HIV epidemic response, especially for marginalized populations.

A Review of Network Models for HIV Spread

BACKGROUND

HIV/AIDS has been a global health crisis for over 4 decades. Network models, which simulate human behavior and intervention impacts, have become an essential tool in guiding HIV prevention strategies and policies. However, no comprehensive survey of network models in HIV research has been conducted. This article fills that gap, offering a summary of past work and future directions to engage more researchers and inform policy related to eliminating HIV.

SETTING

Network models explicitly represent interactions between individuals, making them well-suited to study HIV transmission dynamics. Two primary modeling paradigms exist: a mechanistic approach from applied mathematics and a statistical approach from the social sciences. Each has distinct strengths and weaknesses, which should be understood for effective application to HIV research.

METHODS

We conducted a systematic review of network models used in HIV research, detailing the model types, populations, interventions, behaviors, datasets, and software used, while identifying potential future research directions.

RESULTS

Network models are particularly valuable for studying behaviors central to HIV transmission, such as partner selection and treatment adherence. Unlike traditional models, they focus on individual behaviors, aligning them with clinical practice. However, more accurate network data are needed for better model calibration and actionable insights.

CONCLUSIONS

This article serves as a point of reference for HIV researchers interested in applying network models and understanding their limitations. To our knowledge, this is the most comprehensive review of HIV network models to date.

Assessing Consistency of Respondent-driven Sampling Estimators by Using Repeated Surveys among People Who Inject Drugs (PWID) in New Jersey

Respondent-driven sampling (RDS) is widely used to sample populations with higher risk of HIV infection for whom no sampling frames exist. However, few studies have been done to assess the consistency of RDS estimators in real world settings. We conducted an assessment study on the consistency of RDS estimators using data from the National HIV Behavioral Surveillance - People Who Inject Drugs surveys in Newark, New Jersey from 2005 to 2018. Population parameter estimates based on RDS-I, RDS-II, Gile's SS, and HCG were compared longitudinally and cross-sectionally. Population homophily statistics and differential recruitment statistics were estimated and compared. Convergence plots were used for RDS diagnosis. Sensitivity analyses were conducted on population size estimates and seeds biases. By comparing time-insensitive population parameters and population homophily statistics estimated by four RDS estimators, the study found that RDS-II and Gile's SS could provide longitudinally and cross-sectionally consistent estimates and population homophily statistics on gender and sexual orientation. Cross-sectional comparison of time-sensitive population parameter estimates also supported the consistency of RDS-II and Gile's SS. However, RDS-I and HCG did not perform well in those comparisons. In conclusion, RDS estimators may not address all inconsistencies, but RDS-II and Gile's SS are recommended to weight RDS samples given enough consistency was observed in them.

The Development and the Assessment of Sampling Methods for Hard-to-Reach Populations in HIV Surveillance

Due to stigma or legal issues, populations with higher HIV risk are often hard to reach, which impedes accurate population estimation of HIV burden. To better sample hard-to-reach populations (HTRPs) for HIV surveillance, various sampling methods have been designed and/or used since HIV epidemic following the first reported AIDS cases in 1981. This paper describes the development and the assessment (i.e., validity and reproducibility) of approximately eight sampling methods (e.g., convenience sampling, snowball sampling, time location sampling, and respondent-driven sampling) for HTRPs in HIV surveillance, with a focus on respondent-driven sampling (RDS). Compared to other methods, RDS has been greatly assessed. However, current evidence is still inadequate for RDS to be considered the best option for sampling HTRPs. The field must continue to assess RDS and to develop new sampling approaches or modifications to existing approaches.

Assessing reliability of naïve respondent-driven sampling samples by using repeated surveys among people who inject drugs (PWID) in New Jersey

INTRODUCTION

Respondent-driven sampling (RDS) is widely used to sample populations with higher risk of HIV infection for whom no sampling frames exist. However, few studies have been done to assess the reliability of RDS in real world settings.

METHODS

We assessed the reliability of naïve RDS samples using five rounds of the National HIV Behavioral Surveillance - People Who Inject Drugs surveys in Newark, New Jersey from 2005 to 2018. Specifically, we compared the distributions of time-insensitive demographic characteristics in temporally adjacent RDS samples with Monte Carlo Two-Sample Kolmogorov-Smirnov Test with 100,000 replicates. The distributions of time-sensitive demographic characteristics were also compared as sensitivity analyses.

RESULTS

The study showed that repeated RDS samples among people who inject drugs in the greater Newark area, New Jersey were reliable in most of time-insensitive demographics and recruitment homophily statistics. Sensitivity analyses of time-sensitive demographics also presented consistencies in most of temporally adjacent samples.

CONCLUSIONS

In conclusion, RDS has the potential to provide reliable samples, but demographic characteristics of RDS samples may be easily biased by homophily. Future studies using RDS may need to pay more attention to potential homophily bias and consider necessary diagnostic procedures and sample adjustments.

Social networks, secondary syringe exchange, and opioid agonist therapy retention among people who inject drugs in Hartford, CT

BACKGROUND

Opioid agonist therapies (OAT) and  harm reduction such as syringe service programs (SSP) have been shown to be effective in preventing adverse outcomes such as overdose deaths, HIV and Hepatitis C infections among people who inject drugs (PWID). The importance of social network influence on disease transmission is well established, yet the interplay between harm reduction and network structures is, generally, not well understood. This study aims to analyze how social networks can mediate the harm reduction effects associated with secondary exchange through syringe service programs (SSP) and opioid agonist therapies (OAT) among injection network members.

METHODS

Sociometric data on networks on people who inject drugs from Hartford, CT, which were collected in 2012-2013, provided assessment of risk behaviors among 1574 injection network members, including participation in OAT and SSP. Subject's network characteristics were examined in relation to retention in OAT, as well as secondary syringe exchange using exponential random graph model (ERGM) and regression.

RESULTS

Based on the analysis, we found that probability of individuals being retained in OAT was positively associated with the OAT retention status of their peers within the network. Using simulations, we found that higher levels of positive correlation of OAT retention among network members can result in reduced risk of transmission of HIV to network partners on OAT. In addition, we found that secondary syringe exchange engagement was associated with higher probability of sharing of paraphernalia and unsterile needles at the network level.

CONCLUSIONS

Understanding how networks mediate risk behaviors is crucial for making progress toward ending the HIV epidemic.

Using the network scale-up method to characterise kidney trafficking in Kalai Upazila, Bangladesh

This study aimed to estimate the prevalence of illegal kidney sales in Kalai Upazila, Bangladesh, using the Network Scale-Up Method (NSUM), an ego-centric network survey-based technique used to estimate the size of hidden populations. The study estimated the size of the kidney seller population, analysed the profiles of kidney sellers and kidney brokers and investigated the characteristics of villagers who are more likely to be connected to kidney sellers to identify possible biases of the NSUM estimate. The study found that the prevalence of kidney trafficking in Kalai Upazila was between 1.98% and 2.84%, which is consistent with the estimates provided by a local leader and reporters, but with much narrower bounds. The study also found that a large proportion of kidney sellers and brokers were men (over 70% and 90%, respectively) and relatively young (mean age of 33 and 39, respectively). Specific reasons for kidney sales included poverty (83%), loan payment (4%), drug addiction (2%) and gambling (2%). While most reported male sellers were farmers (56%) and female sellers were housewives (78%) in need of money, most reported brokers were characterised as rich, well-known individuals.

Incidence of and Experiences with Abortion Attempts in Soweto, South Africa: Respondent-Driven Sampling Study

BACKGROUND

Estimation of abortion incidence, particularly in settings where most abortions occur outside of health facility settings, is critical for understanding information gaps and service delivery needs in different settings. However, the existing methods for measuring out-of-facility abortion incidence are plagued with methodological challenges. Respondent-driven sampling (RDS) may offer a methodological improvement in the estimation of abortion incidence.

OBJECTIVE

In this study, we tested the feasibility of using RDS to recruit participants into a study about abortion and estimated the proportion of people who ever attempted abortion as well as 1-year and 5-year incidence of abortion (both in-facility and out-of-facility settings) among women of reproductive age in Soweto, South Africa.

METHODS

Participants were eligible if they identified as a woman; were aged between 15 and 49 years; spoke English, Tswana, isiZulu, Sotho, or Xhosa; and lived in Soweto. Working with community partners, we identified 11 seeds who were provided with coupons to refer eligible peers to the study. Upon arrival at the study site, the recruits completed an interviewer-administered questionnaire that solicited information about demographic characteristics, social network composition, health behaviors, sexual history, pregnancy history, and experience with abortion; recruits also received 3 recruitment coupons. Recruitment was tracked using coupon numbering. We used the RDS-II estimator to estimate the population proportions of demographic characteristics and our primary outcome, the proportion of people who ever attempted abortion.

RESULTS

Between April 4, 2018, and December 17, 2018, 849 eligible participants were recruited into the study. The estimated proportion of people who ever attempted abortion was 12.1% (95% CI 9.7%-14.4%). A total of 7.1% (95% CI 5.4%-8.9%) reported a facility-based abortion, and 4.4% (95% CI 3.0%-5.8%) reported an out-of-facility abortion.

CONCLUSIONS

The estimated proportion of people who ever attempted abortion of 12% (102/849) in our study likely represents a substantial underestimation of the actual proportion of abortion attempts among this study population-representing a failure of the RDS method to generate more reliable estimates of abortion incidence in our study. We caution against the use of RDS to measure the incidence of abortion because of persistent concerns with underreporting but consider potential alternative applications of RDS with respect to the study of abortion.

Missed opportunities for healthcare providers to discuss HIV preexposure prophylaxis with people who inject drugs

OBJECTIVE

To identify missed opportunities for healthcare providers to discuss HIV pre-exposure prophylaxis (PrEP) with people who inject drugs (PWID).

METHODS

Participants were 395 HIV-negative PWID recruited for the 2018 National HIV Behavioral Surveillance survey in San Francisco, California via respondent-driven sampling. Adjusted logistic regression tested whether discussing PrEP with a provider in the last year was associated with sociodemographic characteristics, structural factors, and accessing HIV/STI and substance use treatment services.

RESULTS

Most PWID (86.3%) reported seeing a healthcare provider, but only 15.0% of these reported discussing PrEP with a healthcare provider. PWID who were sexual minority men had greater odds of having a discussion about PrEP with a healthcare provider than PWID who were heterosexual men (aOR=3.42, 95% CI=1.21-9.73) or heterosexual women (aOR=3.69, 95% CI=1.08-12.62). Additionally, factors associated with discussing PrEP included: being tested for HIV (aOR=4.29, 95% CI=1.21-15.29), having a healthcare provider recommend HIV testing (aOR=2.95, 95% CI=1.23-7.06), and receiving free condoms from a prevention program (aOR=5.45, 95% CI=1.78-16.65).

CONCLUSIONS

In the face of low PrEP uptake, continuing HIV transmission, and many missed opportunities to discussed PrEP (e.g., PWID who are women, substance use treatment services), these findings from San Francisco indicate that healthcare providers and public health efforts need to systematically offer PrEP to PWID. Additional research may clarify missed opportunities in other locations as well as the impact of COVID-19.

HIV prevalence, engagement in care, and risk behavior among trans women, San Francisco: Evidence of recent successes and remaining challenges

BACKGROUND

Trans women have high HIV prevalence and lag behind 90-90-90 targets for HIV care. In San Francisco in 2017, 96% of trans women were aware of their status, 75% were on antiretroviral therapy, 88% had viral suppression. Initiatives to address gaps include peer navigators, free gender-affirming surgery, and housing. Our study updates HIV prevalence and engagement in care among trans women.

METHODS

Cross-sectional community-based survey of trans women living in San Francisco sampled by respondent-driven sampling, 7/2019-2/2020 (N = 201). Eligibility was: self-identified trans women or other gender and assigned male at birth; living in San Francisco; English/Spanish-speaking; and 18 years or older.

RESULTS

HIV prevalence was 42.3% (95%CI 35.4.-49.4) and associated with having a partner who injected drugs (adjusted odds ratio [AOR] 3.30, 95%CI 1.58-6.90), ever injected drugs (AOR 2.28, 95%CI 1.06-4.89), cost not a barrier to healthcare (AOR 2.63, 95%CI 1.02-6.67), emotional support from family (AOR 2.85, 95%CI 1.43-5.65), and Black/African-American (AOR 2.59, 95%CI 1.16-5.79). Of trans women with HIV, 92.9% were previously diagnosed, 89.9% were on ART, 91.5% reported viral suppression.

CONCLUSIONS

Trans women met 90-90-90 targets in 2020, at 93-90-92. Interventions need to reach Black/African-American trans women, trans women who inject drugs, and partners of trans women.

Fish consumption and awareness of fish advisories among Burmese refugees: A respondent-driven sampling study in Milwaukee, Wisconsin

BACKGROUND

Since 2000, more than 6000 Burmese refugees were resettled in Wisconsin. The Burmese diet is traditionally rich in fish and fish products, and studies show that Burmese refugees continue to rely on local waterbodies for food. Given that Wisconsin has five Areas of Concern (AOC) that are severely affected by pollution, long-term exposure to contaminants in sport-caught fish is a health concern. To better understand fish consumption among Burmese refugees, we conducted a biomonitoring study in Milwaukee. The present study examined Burmese refugees' fish consumption habits and awareness of fish advisories.

METHODS

We used respondent-driven sampling (RDS) methodology to recruit Burmese refugees in Milwaukee. RDS Analysis Tool 7.1 was used to obtain adjusted population estimates for demographic characteristics, fish consumption habits, and awareness of fish advisories. Homophily and equilibrium were investigated to evaluate the effectiveness of RDS in recruitment.

RESULTS

Initiated by five active seeds, we recruited 103 respondents to participate in the study. Respondents had a strong preference to recruit those with the same ethnicity (Homophily-score: 0.614 to 0.699) and a relatively weak preference to recruit those with the same sex (Homophily-score: 0.188 to 0.222) to participate in our study. The majority (72.5%) of respondents were women of childbearing age (WCBA). Most (68.5%) had 8th grade or less education. Regarding sportfish consumption per month in the last year, 30.6% reported eating 1-3 meals and 21.2% reported eating more than 3 meals. When asked about purchased fish consumption per month, 26.3% reported eating 1-3 meals. The overwhelming majority were not aware of safe-eating sportfish guidelines for Wisconsin (88.3%) or Milwaukee waterbodies (96.6%).

CONCLUSIONS

RDS is an effective methodology to recruit hard-to-reach populations, such as the Burmese surveyed in this study. High percentages of WCBA eating potentially contaminated sportfish meals, low awareness of consumption advisories, and limited economic resources make the Burmese population more likely to be exposed to contaminants. Health education efforts should be focused in this vulnerable population, particularly among Burmese WCBA.

Sexual Mixing and HIV Transmission Potential Among Greek Men Who have Sex with Men: Results from SOPHOCLES

HIV incidence among men who have sex with men (MSM) in Greece remains unchanged despite effective response to a recent outbreak among people who inject drugs (PWID). Network factors are increasingly understood to drive transmission in epidemics. The primary objective of the study was to characterize MSM in Greece, their sexual behaviors, and sexual network mixing patterns. We investigated the relationship between serostatus, sexual behaviors, and self-reported sex networks in a sample of MSM in Athens, Greece, generated using respondent driven sampling. We estimated mixing coefficients (r) based on survey-generated egonets. Additionally, multiple logistic regression was used to estimate adjusted odds ratios (AOR) and to assess relationships between serostatus, sexual behaviors, and sociodemographic indicators. A sample of 1,520 MSM participants included study respondents (n = 308) and their network members (n = 1,212). Mixing based on serostatus (r = 0.12, σr = 0.09-0.15) and condomless sex (r = 0.11, σr = 0.07-0.14) was random. However, mixing based on sex-drug use was highly assortative (r = 0.37, σr = 0.32-0.42). This study represents the first analysis of Greek MSM sexual networks. Our findings highlight protective behavior in two distinct network typologies. The first typology mixed assortatively based on serostatus and sex-drug use and was less likely to engage in condomless sex. The second typology mixed randomly based on condomless sex but was less likely to engage in sex-drug use. These findings support the potential benefit of HIV prevention program scale-up for this population including but not limited to PrEP.

Homelessness, HIV testing, and the reach of public health efforts for people who inject drugs, San Francisco, California

BACKGROUND

There is a dearth of literature that explicitly examines associations between housing and HIV testing among people who inject drugs (PWID). Thus, the present study investigated the links between housing status and HIV testing for PWID.

METHODS

Respondent-driven sampling recruited 382 HIV-negative PWID, who completed structured interviews in San Francisco. Logistic regression determined whether housing statuses in the past 12 months ([1] owned/rented, [2] single-room occupancy hotels [SROs], [3] living with friends/family/partners, [4] shelters, [5] outdoors) were associated with getting HIV tested in the past 12 months while adjusting for sociodemographics and receptive sharing of injection paraphernalia in the past 12 months.

RESULTS

PWID who lived in SROs had greater odds of being tested for HIV than PWID who did not live in SROs (aOR = 1.95, CI_.95: 1.06-3.60) while adjusting for covariates. Although bivariable analyses indicated that receptively sharing syringes was more common for PWID who lived with others (χ²[3] = 7.94, p = 0.047) or lived outdoors (χ²[3] = 9.50, p = 0.023) than those who did not, respectively, PWID who lived with others (aOR = 1.72, CI_.95 = 0.95-3.14) or lived outdoors (aOR = 1.37, CI_.95 = 0.74-2.53) did not show greater odds of HIV testing in multivariable analyses.

CONCLUSIONS

PWID who lived in SROs had greater odds of HIV testing than PWID who did not live in SROs. Although PWID who lived with others or outdoors showed greater HIV risk, they did not show greater odds of HIV testing. Public health efforts may be reaching PWID in SROs, but more work is needed to reach PWID who live with other people or outdoors.

Modeling Combination Hepatitis C Virus Treatment and Prevention Strategies in a Network of People Who Inject Drugs in the United States

BACKGROUND

Hepatitis C virus (HCV) treatment as prevention (TasP) strategies can contribute to HCV microelimination, yet complimentary interventions such as opioid agonist therapies (OAT) with methadone or buprenorphine and syringe services programs (SSPs) may improve the prevention impact. This modeling study estimates the impact of scaling up the combination of OAT and SSPs with HCV TasP in a network of people who inject drugs (PWID) in the United States.

METHODS

Using empirical data from Hartford, Connecticut, we deployed a stochastic block model to simulate an injection network of 1574 PWID. We used a susceptible-infected model for HCV and human immunodeficiency virus to evaluate the effectiveness of several HCV TasP strategies, including in combination with OAT and SSP scale-up, over 20 years.

RESULTS

At the highest HCV prevalence (75%), when OAT coverage is increased from 10% to 40%, combined with HCV treatment of 10% per year and SSP scale up to 40%, the time to achieve microelimination is reduced from 18.4 to 11.6 years. At the current HCV prevalence (60%), HCV TasP strategies as low as 10% coverage per year may achieve HCV microelimination within 10 years, with minimal impact from additional OAT scale-up. Strategies based on mass initial HCV treatment (50 per 100 PWID the first year followed by 5 per 100 PWID thereafter) were most effective in settings with HCV prevalence of 60% or lower.

CONCLUSIONS

Scale-up of HCV TasP is the most effective strategy for microelimination of HCV. OAT scale-up, however, scale-up may be synergistic toward achieving microelimination goals when HCV prevalence exceeds 60% and when HCV treatment coverage is 10 per 100 PWID per year or lower.

Risky injection practices and HCV awareness in Chiang Mai Province, Thailand: a respondent-driven sampling study of people who inject drugs

Background

People who inject drugs (PWID) are the most exposed to hepatitis C virus (HCV). In Thailand, drug use is highly criminalized, and harm reduction services are scarce. This study estimates risky injection practices and assesses the proportion of HCV awareness and screening in the PWID population in Northern Thailand.

Methods

We used respondent-driven sampling (RDS) to recruit PWID in Chiang Mai Province. Social and behavioural data were collected through face-to-face interviews at an addiction treatment facility. Weighted population estimates were calculated to limit biases related to the non-random sampling method. Univariate and multivariate analyses were performed to study factors associated with HCV awareness and screening.

Results

One hundred seventy-one PWID were recruited between April 2016 and January 2017. Median age was 33 (Interquartile range: 26–40) years, 12.2% were women, and 49.4% belonged to a minority ethnic group. Among participants, 76.8% injected heroin, 20.7% methadone, and 20.7% methamphetamine. We estimate that 22.1% [95% CI: 15.7–28.6] of the population had shared needles in the last 6 months and that 32.0% [95% CI: 23.6–40.4] had shared injection material. Only 26.6% [95% CI: 17.6–35.6] had heard of HCV. Factors independently associated with knowledge of HCV included belonging to a harm reduction organization (adjusted odds ratio (aOR) = 5.5 [95% CI: 2.0–15.3]) and voluntary participation in a drug rehabilitation programme (aOR = 4.3 [95% CI: 1.3–13.9]), while Lahu ethnicity was negatively associated (aOR = 0.3 [95% CI: 0.1–0.9]). We estimate that 5% of the PWID population were screened for HCV; the only factor independently associated with being screened was membership of a harm reduction organization (aOR = 5.7 [95% CI: 1.6–19.9]).

Conclusion

Our study reveals that the PWID population is poorly informed and rarely screened for HCV, despite widespread risky injection practices. A public health approach aimed at reducing the incidence of HCV should target the PWID population and combine harm reduction measures with information and destigmatization campaigns. Civil society organizations working with PWID are a major asset for the success of such an approach, based on their current positive interventions promoting awareness of and screening for HCV.

HIV Prevalence and Associated Risks in a Respondent-Driven Sample of Illicit Stimulant Users in a Southern United States City

Stimulant abuse is a major contributor to HIV transmission in the United States, yet HIV prevalence among persons who use illicit stimulants remains unknown. We implemented respondent driven sampling (RDS) to estimate the prevalence of HIV infection in this high-risk population. We also examined RDS-adjusted rates of risk behaviors among HIV-positive and HIV-negative participants. Recruited from seven seeds, our sample of 387 participants was 46% female, 89% African American, and 45.94 years old on average. Participants were predominantly non-injection cocaine users, had large networks of stimulant users, and reported an established relationship with their recruiter. The adjusted population proportion of HIV infection was 0.07 (0.04, 0.11). The majority of sexually active participants reported engagement in risk behaviors (73%), but rates generally did not differ by HIV status. Our results highlight that stimulant use is a risk factor for HIV infection. This study also demonstrates that RDS is a very effective strategy for reaching stimulant users in the community.

Exploring Mechanisms of Recruitment and Recruitment Cooperation in Respondent Driven Sampling

Respondent driven sampling (RDS) is a sampling method designed for hard-to-sample groups with strong social ties. RDS starts with a small number of arbitrarily selected participants ("seeds"). Seeds are issued recruitment coupons, which are used to recruit from their social networks. Waves of recruitment and data collection continue until reaching a sufficient sample size. Under the assumptions of random recruitment, with-replacement sampling, and a sufficient number of waves, the probability of selection for each participant converges to be proportional to their network size. With recruitment noncooperation, however, recruitment can end abruptly, causing operational difficulties with unstable sample sizes. Noncooperation may void the recruitment Markovian assumptions, leading to selection bias. Here, we consider two RDS studies: one targeting Korean immigrants in Los Angeles and in Michigan; and another study targeting persons who inject drugs in Southeast Michigan. We explore predictors of coupon redemption, associations between recruiter and recruits, and details within recruitment dynamics. While no consistent predictors of noncooperation were found, there was evidence that coupon redemption of targeted recruits was more common among those who shared social bonds with their recruiters, suggesting that noncooperation is more likely to be a feature of recruits not cooperating, rather than recruiters failing to distribute coupons.

Stigma, discrimination, violence, and HIV testing among men who have sex with men in four major cities in Ghana

LGBTQ populations experience human rights abuses worldwide; data need to document the health impact of these experiences in Africa. In Ghana, we measured events of sexuality-based stigma, discrimination, and violence among men who have sex with men (MSM) and the impact on HIV testing behavior. Data are from respondent-driven sampling surveillance surveys in Accra/Tema, Kumasi, Cape Coast/Takoradi, and Koforidua. Discrimination was common among MSM: 6.2%-30.6% were refused services, 29.0%-48.9% experienced verbal/symbolic violence, 2.8%-12.8% experienced physical violence, 12.3%-30.0% experienced sexual violence due to their sexuality in the preceding year. MSM who experienced sexual violence in their first male sexual encounter were less likely to ever test for HIV in Accra/Tema and Cape Coast/Takoradi. Further studies are needed to examine the impact of stigma and violence on MSM's HIV health-seeking behavior in Ghana. Structural interventions are needed to mitigate the consequences of stigma and discrimination on MSM health and well-being.

Low PrEP Awareness and Use Among People Who Inject Drugs, San Francisco, 2018

We examined PrEP awareness and use among people who inject drugs (PWID) in San Francisco in 2018. Of 397 respondents not known to be HIV positive, 56.7% had heard of PrEP, 38.9% knew that PrEP can prevent HIV transmission from sharing injection equipment, 13.6% had discussed PrEP with a health care provider, and 3.0% had used PrEP in the last 12 months. All seven male PWID who had used PrEP were also men who had sex with men. There is urgent need to improve messaging on PrEP's effectiveness for PWID and to tailor ways of engaging PWID in PrEP programs.

Divergent estimates of HIV incidence among people who inject drugs in Ukraine

BACKGROUND

Divergent estimates of HIV incidence among people who inject drugs (PWID) in Ukraine have been reported in modeling studies, longitudinal cohort studies, and recent infection assays used in cross-sectional surveys. Estimates range from 0.65 to 24.8 infections per 100 person-years with substantial regional variation. In this paper, we study the sources of this discrepancy.

METHODS

We compared baseline characteristics of study subjects recruited in the cross-sectional integrated bio-behavioral surveillance surveys (IBBS) in 2011 and 2013, with those from the longitudinal network intervention trial (network RCT) conducted between 2010 - 2013, the study that found a remarkably high incidence of HIV among PWID in Ukraine. The analysis was conducted for two cities: Mykolaiv and Odesa.

RESULTS

Significant differences were found in the characteristics of study subjects recruited in the IBBS surveys and the network RCT, in particular in Odesa, where the mismatch in the estimates of HIV incidence is greatest. In Odesa, recent syringe sharing was about three times as prevalent in the network RCT as in the IBBS; 39% of the network RCT and 16-18% of the IBBS participants indicated stimulants rather than opiates as their drug of choice; 97% of respondents in the network RCT and 45% in the IBBS-2013 reported injecting in a group over half of the time; and the average monthly number of injections in the network RCT was about twice that in the IBBS studies.

CONCLUSIONS

Differences in study designs and sampling methodologies may be responsible for the substantial differences in HIV incidence estimates among PWID in Ukraine. The potential sources of selection bias differed between the studies and likely resulted in the recruitment of lower risk individuals into the IBBS studies compared to the network RCT. Risk stratification in the population of PWID may have implications for future surveillance and intervention efforts.

Intervention Reach and Sexual Risk Reduction of a Multi-level, Community-Based HIV Prevention Intervention for Crack Users in San Salvador, El Salvador

This article examines the effects of a multi-level, community-based HIV prevention intervention for crack users residing in low-income neighborhoods in San Salvador, El Salvador conducted between August 2011 and June 2016. The intervention consisted of three components introduced sequentially: (1) rapid HIV testing in community settings; (2) a social network HIV testing intervention; and (3) small group interventions with crack users who were members of the same social network. The intervention was evaluated with an interrupted time series design in which we used respondent-driven sampling to conduct 7 cross-sectional surveys with crack users along a 3-4 month period for each assessment (total n = 1597). Results revealed a significant increase in exposure to the intervention over time with 50% of the participants reporting exposure to one or more of the three components. Getting an HIV test at the community site was associated with reductions in total times each individual had sex without a condom (p < 0.05) compared to those who had been exposed to no intervention components. Being referred by another crack user through the Social Network HIV intervention was also associated with reductions in total numbers of condomless sex (p < 0.05) The cumulative effect of being exposed to more than one intervention component was associated with reductions in total number of times individuals had condomless sex (p < 0.05). In spite of the high level of intervention reach and that self-reported exposure to intervention components was associated with lower sexual risk, reductions in sexual risk over time were not observed in the full sample, indicating that the penetration of HIV prevention components was not sufficient to produce population level change.

Empirical evidence of recruitment bias in a network study of people who inject drugs

Background: Epidemiologic surveys of people who inject drugs (PWID) can be difficult to conduct because potential participants may fear exposure or legal repercussions. Respondent-driven sampling (RDS) is a procedure in which subjects recruit their eligible social contacts. The statistical validity of RDS surveys of PWID and other risk groups depends on subjects recruiting at random from among their network contacts. Objectives: We sought to develop and apply a rigorous definition and statistical tests for uniform network recruitment in an RDS survey. Methods: We undertook a detailed study of recruitment bias in a unique RDS study of PWID in Hartford, CT, the USA in which the network, individual-level covariates, and social link attributes were recorded. A total of n=527 participants (402 male, 123 female, and two individuals who did not specify their gender) within a network of 2626 PWID were recruited. Results: We found strong evidence of recruitment bias with respect to age, homelessness, and social relationship characteristics. In the discrete model, the estimated hazard ratios regarding the significant features of recruitment time and choice of recruitee were: alter's age 1.03 [1.02, 1.05], alter's crack-using status 0.70 [0.50, 1.00], homelessness difference 0.61 [0.43, 0.87], and sharing activities in drug preparation 2.82 [1.39, 5.72]. Under both the discrete and continuous-time recruitment regression models, we reject the null hypothesis of uniform recruitment. Conclusions: The results provide the evidence that for this study population of PWID, recruitment bias may significantly alter the sample composition, making results of RDS surveys less reliable. More broadly, RDS studies that fail to collect comprehensive network data may not be able to detect biased recruitment when it occurs.

Optimizing HIV prevention and care for transgender adults

: Transgender women have recently been acknowledged as a unique and important risk group in HIV research and care. Although transgender men also face specific problems related to HIV infection, less is known about the risk behaviours and HIV prevalence of this important population. This article highlights key issues relating to the epidemiology, prevention, treatment and management of complications of HIV infection in transgender adults living with HIV, and explores future areas for HIV-related research, with the ultimate goal of improving healthcare provision and quality of life for transgender persons worldwide.

Statistical adjustment of network degree in respondent-driven sampling estimators: venue attendance as a proxy for network size among young MSM

We introduce a new venue-informed network degree measure, which we applied to respondent-driven sampling (RDS) estimators. Using data collected from 746 young MSM in 2014-2016 in Chicago, IL, and Houston, TX, we estimated the population seroprevalence of HIV and syphilis and risk/protective behaviors, using RDS estimates with self-reported network size as a standard degree measure as well as our proposed venue-informed degree measure. The results indicate that the venue-informed degree measure tended to be more efficient (smaller variance) and less biased than the other measure in both cities sampled. Venue attendance-adjusted network size may provide a more reliable and accurate degree measure for RDS estimates of the outcomes of interest.

Multiple strategies to identify HIV-positive black men who have sex with men and transgender women in New York City: a cross-sectional analysis of recruitment results

INTRODUCTION

Black men who have sex with men and transgender women are at high risk for HIV infection, but are more likely to be unaware of their infection or not in care for diagnosed HIV compared to other races. Respondent driven sampling has been advanced as a method to reach stigmatized and hidden populations for HIV testing. We compared strategies to recruit black, substance-using men who have sex with men and transgender women to identify newly diagnosed HIV infection, or those previously diagnosed but not in care.

METHODS

The STAR (Seek, Test, and Retain) study (ClinicalTrials.gov NCT01790360) used several recruitment strategies to identify black, substance-using men who have sex with men and transgender women with undiagnosed HIV infection or with previously diagnosed HIV infection but who were not in HIV care. Respondent-driven sampling, community-based recruitment and online advertising were used to recruit participants. Incentivized peer referral was integrated into all recruitment strategies. Participants completed interviewer-administered questionnaires and HIV testing. Demographic and HIV risk-related characteristics and recruitment strategy were summarized and stratified by HIV status. Associations were tested using Pearson's chi-squared, Fisher's exact, and Wilcoxon rank sum tests. Factors associated with HIV-positive diagnosis at p < 0.1 were included in a multivariable logistic regression model.

RESULTS

From July 2012 through October 2015, the study enrolled 1929 participants; 96.3% men who have sex with men and 3.7% transgender women. Behavioural risk factors included recent condomless anal sex (55.6%) and recent substance use during sex (73.1%). HIV prevalence was 8.7%. In multivariable analysis, significant associations with HIV infection included being transgender; non-Hispanic black; gay/homosexual orientation; not homeless; and less likely to have insufficient income for necessities. Among recruitment strategies, respondent driven sampling was least effective in identifying HIV-positive participants.

CONCLUSIONS

Integrating multiple recruitment strategies yielded a large sample of black men who have sex with men and transgender women at substantial risk for HIV. Respondent-driven sampling was less effective than other strategies at identifying men who have sex with men and transgender women with HIV.

Hepatitis C virus treatment as prevention in an extended network of people who inject drugs in the USA: a modelling study

BACKGROUND

Chronic infections with hepatitis C virus (HCV) and HIV are highly prevalent in the USA and concentrated in people who inject drugs. Treatment as prevention with highly effective new direct-acting antivirals is a prospective HCV elimination strategy. We used network-based modelling to analyse the effect of this strategy in HCV-infected people who inject drugs in a US city.

METHODS

Five graph models were fit using data from 1574 people who inject drugs in Hartford, CT, USA. We used a degree-corrected stochastic block model, based on goodness-of-fit, to model networks of injection drug users. We simulated transmission of HCV and HIV through this network with varying levels of HCV treatment coverage (0%, 3%, 6%, 12%, or 24%) and varying baseline HCV prevalence in people who inject drugs (30%, 60%, 75%, or 85%). We compared the effectiveness of seven treatment-as-prevention strategies on reducing HCV prevalence over 10 years and 20 years versus no treatment. The strategies consisted of treatment assigned to either a randomly chosen individual who injects drugs or to an individual with the highest number of injection partners. Additional strategies explored the effects of treating either none, half, or all of the injection partners of the selected individual, as well as a strategy based on respondent-driven recruitment into treatment.

FINDINGS

Our model estimates show that at the highest baseline HCV prevalence in people who inject drugs (85%), expansion of treatment coverage does not substantially reduce HCV prevalence for any treatment-as-prevention strategy. However, when baseline HCV prevalence is 60% or lower, treating more than 120 (12%) individuals per 1000 people who inject drugs per year would probably eliminate HCV within 10 years. On average, assigning treatment randomly to individuals who inject drugs is better than targeting individuals with the most injection partners. Treatment-as-prevention strategies that treat additional network members are among the best performing strategies and can enhance less effective strategies that target the degree (ie, the highest number of injection partners) within the network.

INTERPRETATION

Successful HCV treatment as prevention should incorporate the baseline HCV prevalence and will achieve the greatest benefit when coverage is sufficiently expanded.

FUNDING

National Institute on Drug Abuse.

HIV Risk, Prevalence, and Access to Care Among Men Who Have Sex with Men in Lebanon

Little is known about HIV prevalence and risk among men who have sex with men (MSM) in much of the Middle East, including Lebanon. Recent national-level surveillance has suggested an increase in HIV prevalence concentrated among men in Lebanon. We undertook a biobehavioral study to provide direct evidence for the spread of HIV. MSM were recruited by respondent-driven sampling, interviewed, and offered HIV testing anonymously at sites located in Beirut, Lebanon, from October 2014 through February 2015. The interview questionnaire was designed to obtain information on participants' sociodemographic situation, sexual behaviors, alcohol and drug use, health, HIV testing and care, and experiences of stigma and discrimination. Individuals not reporting an HIV diagnosis were offered optional, anonymous HIV testing. Among the 292 MSM recruited, we identified 36 cases of HIV (12.3%). A quarter of the MSM were born in Syria and recently arrived in Lebanon. Condom use was uncommon; 65% reported condomless sex with other men. Group sex encounters were reported by 22% of participants. Among the 32 individuals already aware of their infection, 30 were in treatment and receiving antiretroviral therapy. HIV prevalence was substantially increased over past estimates. Efforts to control future increases will have to focus on reducing specific risk behaviors and experience of stigma and abuse, especially among Syrian refugees.