Respondent-driven Sampling Study Research Articles

Respondent Driven Sampling for Immigrant Populations: A Health Survey of Foreign-Born Korean Americans.

This study examined feasibility and methodological utilities of respondent driven sampling (RDS) for Korean immigrants. We conducted the Health and Life Study of Koreans (HLSK), a Web-based RDS study targeting foreign-born Korean Americans. Through chain referrals, n = 638 participated. Geographic coverage and estimates of HLSK were compared to foreignborn Korean samples in the American Community Survey and the California Health Interview Survey as benchmarks. Compared to the benchmarks, HLSK fared well on the geographic coverage, household type and size, employment and health insurance but over-captured those who were younger, more recent immigrants, with higher education and with disability. Existing RDS-specific estimators were largely ineffective. Conclusions. RDS may serve as a cost-effective tool for recruiting recent immigrants, a harder-to-recruit subgroup within minorities. However, recruitment noncooperation posed operational challenges, a critical gap in the literature. This leaves RDS yet to be a reliable methodology.

HIV risks and engagement with care among female sex workers: findings from a respondent-driven sampling study, Nsanje, Malawi

HIV risks and engagement with care among female sex workers: findings from a respondent-driven sampling study, Nsanje, Malawi

HIV risk behavior and HIV testing among rural and urban men who have sex with men in Zhejiang Province, China: A respondent-driven sampling study.

Currently, human immunodeficiency virus (HIV) sentinel surveillance among men who have sex with men (MSM) in China conducted in large and medium-sized cities, and no HIV sentinel surveillance conducted in rural areas. HIV testing and intervention is predominantly conducted in urban areas, there have been a limited number of studies in rural areas MSM, it is necessary to conduct the investigation of HIV risk sexual behavior, HIV testing among rural and urban MSM. Between December 2013 and August 2015, a cross-sectional study was conducted in rural and urban areas in Zhejiang Province using respondent-driven sampling (RDS). Participants completed face-to-face interviewer-administered questionnaire surveys and were tested for HIV. A total of 710 MSM participants were recruited, of whom 36.1% were from rural areas. The overall HIV prevalence was 16.6%, and was considerably lower among MSM living in rural areas (3.9%) than those living in urban areas (24.2%). 61.1% participants had not condom use with male sexual behavior in the past 6 months (86.7% in rural areas and 46.7% in urban areas). The social demographic and behavioral characteristics had significance difference among rural and urban MSM. Multivariate logistic regression revealed that, compared to men living in urban areas, MSM living in rural areas MSM were more likely to use dating apps to find sexual partners, were more likely to engage in bisexual behavior, and had lower condom use. 43.0% participants had been tested for HIV in the past year (41.8% in rural areas and 43.6% in urban areas). Multivariate logistic regression also revealed that among participants living in rural areas, having rural health insurance and not accepting HIV intervention were associated with lower HIV testing rates, while a higher monthly income and through use of internet to find sexual partner were associated with higher rates of HIV testing. High risk behavior was prevalent, and HIV testing rates were low among MSM living in rural areas compare to urban areas in Zhejiang Province, therefore, preventative intervention measures should be immediately among rural MSM urgently to reduce HIV transmission and to promote HIV testing.

Model-based Respondent-driven sampling analysis for HIV prevalence in brazilian MSM

Respondent Driven Sampling study (RDS) is a population sampling method developed to study hard-to-reach populations. A sample is obtained by chain-referral recruitment in a network of contacts within the population of interest. Such self-selected samples are not representative of the target population and require weighing observations to reduce estimation bias. Recently, the Network Model-Assisted (NMA) method was described to compute the required weights. The NMA method relies on modeling the underlying contact network in the population where the RDS was conducted, in agreement with directly observable characteristics of the sample such as the number of contacts, but also with more difficult-to-measure characteristics such as homophily or differential characteristics according to the response variable. Here we investigated the use of the NMA method to estimate HIV prevalence from RDS data when information on homophily is limited. We show that an iterative procedure based on the NMA approach allows unbiased estimations even in the case of strong population homophily and differential activity and limits bias in case of preferential recruitment. We applied the methods to determine HIV prevalence in men having sex with men in Brazilian cities and confirmed a high prevalence of HIV in these populations from 3.8% to 22.1%.

Spatial and sociodemographic correlates of gambling participation and disorder among female Filipino migrant workers in Macao, People's Republic of China

Background and aimsCorrelates and risk factors for gambling disorder among vulnerable or transient populations such as transnational migrant workers are unknown. The current study examined sociodemographic and spatial correlates of gambling disorder among female Filipino domestic workers in Macao (SAR), China. DesignSurvey-based, respondent-driven sampling study administered from November 2016 to August 2017. SettingMacao (SAR), which encompassed 38 casinos within its 30.4 km2 area at the time of this study. ParticipantsRepresentative sample of N = 1194 female Filipino domestic workers in Macao. MeasurementsSymptoms of gambling disorder based on Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). Correlates evaluated included sociodemographic information, proximity to venues, perceived social support, and symptoms of depression and anxiety. FindingsPrevalence of gambling disorder was 5.1%. Multivariable regression analyses indicated that likelihood of gambling participation (i.e., ever gambling) was associated with current indebtedness (RR = 1.56, 95%CI = 1.08–2.25, p = .017) and worse self-reported health (RR = 1.31, 95%CI = 1.04–1.65, p = .02). Increased symptoms of gambling disorder were independently associated with lower perceived social support (RR = 0.92, 95%CI = 0.87–0.98, p = .006), increased dependents relying upon monthly remittances (RR = 1.10, 95%CI = 1.06–1.16, p < .001), increased depression severity (RR = 1.16, 95%CI = 1.07–1.25, p < .001), decreased salary quintile (RR = 0.97, 95%CI = 0.94–1.00, p = .04), and proximity to the nearest Mocha Club gaming venues (RR = 1.04, 95%CI = 1.02–1.07, p = .005). The association between proximity to casinos and increased symptoms of gambling disorder was significant only for domestic workers living apart from employers (RR = 1.07, 95%CI = 1.00–1.14, p = .04). ConclusionsIncreased spatial proximity to gambling venues and greater financial and psychosocial burdens are associated with gambling disorder among domestic workers in Macao.

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

ABSTRACTBackground: 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 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.

A longitudinal analysis of cannabis use and mental health symptoms among gay, bisexual, and other men who have sex with men in Vancouver, Canada

BackgroundCannabis use, anxiety, and depression are common among gay, bisexual, and other men who have sex with men (gbMSM) and some report using cannabis to manage mental health symptoms. MethodsSexually-active gbMSM aged ≥16 years were recruited into a longitudinal cohort through respondent-driven sampling and completed study visits every six months. Data on demographics, drug use, and anxiety and depression symptoms were collected via a self-administered computer-based survey. A study nurse determined previous mental health diagnoses and treatment. Using multivariable generalized linear mixed models, we examined factors associated with regular cannabis use (≥weekly in the previous 3 months) and, among individuals who reported anxiety or depression/bipolar diagnoses, factors associated with moderate/severe anxiety or depression symptoms. ResultsOf 774 participants (551 HIV-negative, 223 HIV-seropositive), 250 (32.3%) reported regular cannabis use, 200 (26.4%) reported ever being diagnosed with anxiety, and 299 (39.3%) reported ever being diagnosed with depression or bipolar disorder at baseline. Regular cannabis use was positively associated with HIV-seropositivity (aOR = 2.23, 95%CI:1.40–3.54) and previous mental health diagnosis (aOR = 1.52, 95%CI: 1.00–2.31, p = 0.05). Among those previously diagnosed with anxiety or depression/bipolar disorder, regular cannabis use was not associated with moderate/severe anxiety (aOR = 1.16, 95%CI:0.69–1.94) or depression symptoms (aOR = 0.96, 95%CI:0.59–1.58), respectively. LimitationsBecause of observational study design, we are unable to determine absolute effect. ConclusionsRegular cannabis use was more likely among HIV-positive gbMSM and those previously diagnosed with a mental health disorder. No association was found between regular cannabis use and severity of anxious or depressive symptoms among those diagnosed with these conditions.

Intimate partner violence and receptive syringe sharing among women who inject drugs in Indonesia: A respondent-driven sampling study

BackgroundIntimate partner violence (IPV) and HIV are overlapping public health problems that disproportionately affect women who inject drugs. Little is known about the relationship between IPV and HIV-related unsafe injecting practices among women in low- and middle-income settings. This study investigated whether IPV victimisation was associated with receptive syringe sharing among women who inject drugs in Indonesia. MethodsRespondent-driven sampling (RDS) was used to recruit 731 women aged 18+ years, injecting drugs in the preceding 12 months, and residing in Greater Jakarta or Bandung, West Java. Population estimates were derived using the RDS-II estimator. Multivariate logistic regressions assessed relationships between different forms of past-year IPV (i.e. psychological abuse, physical and/or injurious assault, forced sex) and receptive syringe sharing, controlling for city differences and sociodemographic cofactors. ResultsOverall, 21.1% of participants reported engaging in past-month receptive syringe sharing. In multivariate analyses controlling for all forms of IPV, receptive syringe sharing was significantly positively associated with experiencing psychological abuse (OR = 1.86; 95% CI = 1.06,3.24; p = 0.030), physical and/or injurious assault (OR = 1.73; 95% CI = 1.04,2.89; p = 0.034), and several covariates: injecting pharmaceuticals only (versus heroin only) (OR = 3.58; 95% CI = 1.66,7.69; p = 0.001), experiencing unstable housing and/or homelessness (OR = 2.89; 95% CI = 1.41,5.95; p = 0.004), and residing in Bandung, West Java (versus Greater Jakarta) (OR = 2.33; 95% CI = 1.40,3.90; p = 0.001). ConclusionIPV is a significant risk factor for HIV-related injecting risk among women who inject drugs in Indonesia. These findings indicate the urgent need to scale up harm reduction interventions and align existing programs with IPV prevention and support services, with specific efforts targeting the needs of female injectors.

Population-based assessment of health, healthcare utilization, and specific needs of Syrian migrants living in Germany: what is the best sampling method?

Introduction The war in Syria belongs to the most dramatic emergencies in the last decades forcing a large number of people to seek refuge in other countries. Information on health-related aspects and special needs of Syrian migrants is urgently required, especially in countries hosting a considerable number of Syrians like Germany. However, data is scarce and as survey response using traditional sampling methods is usually low, one of the biggest challenges is finding appropriate sampling strategies to obtain representative results. In order to increase survey response in hard-to-reach populations, new methods were developed. One of them is respondent-driven sampling (RDS), a network sampling technique that starts with a small convenience sample of the target population (“seeds”) which is asked to complete the survey. All participants should then invite a limited number of their contacts (“peer-recruited participants”) who are also members of the target population to participate in the survey. In Germany, however, RDS has hardly been used for sampling migrant populations. Therefore, we aimed to assess if respondent-driven sampling (RDS) is a better approach to recruit Syrian migrants for health research than random sampling via the population registry. Methods A cross-sectional study was conducted in Munich, Germany between April and June 2017 inviting adults (18+ years) born in Syria to answer an online questionnaire asking for sociodemographic and health-related information. The participants were recruited using two sampling strategies: random sampling via the population registry (PR) and respondent-driven sampling (RDS). The two study populations were compared to the total sample drawn from the population registry with respect to gender and citizenship. In addition, the two study populations were compared to each other regarding self-reported health status, healthcare utilization, lifestyle factors, social network size, and acculturation. Results Of 374 persons randomly drawn from the population registry, 49 individuals answered the questionnaire completely (response: 13.1%) while via RDS 195 participants were recruited by 16 seeds. More persons possessed German citizenship in the total PR sample (20.5%, 95% CI: 16.5–24.5%) and in the PR study population (28.6%, 95% CI: 15.5–41.7%) than in the RDS study population (0.5%, 95% CI: −0.1 to 1.1%). Participants recruited via the population registry were older, smoked less, reported more often to hold a university degree, and indicated a higher prevalence of chronic diseases, more frequent healthcare utilization, higher scores of acculturation as well as a larger social network compared to the study population obtained via RDS. Conclusions As expected, response was very low among the random sample drawn from the population registry while a larger number of participants were recruited via RDS using only 16 seeds. In addition, the two recruitment strategies led to study populations with substantially different characteristics indicating selection bias in either method. These findings provide valuable information for upcoming population-based studies investigating health-related aspects in migrants indicating that mixed sampling approaches combining various recruitment strategies may enhance representativeness.

Changes in attitudes, risky practices, and HIV and syphilis prevalence among female sex workers in Brazil from 2009 to 2016.

Background:The present study aims at investigating the progress made toward controlling the human immunodeficiency virus (HIV)/AIDS epidemic among female sex workers (FSW) from 2009 to 2016.Methods:The baseline of respondent-driven sampling (RDS) study among FSW was carried out in 2009, in 10 Brazilian municipalities. In 2016, information on FSW were collected in 12 municipalities. The analyses took into account the dependence among observations, resulting from the recruitment chains, and the unequal probabilities of selection, resulting from the different network sizes. We analyzed changes in attitudes and risky behavior practices as well as variations in HIV and syphilis prevalence based on the comparison of 95% confidence intervals for each estimate.Results:Information on 2523 (2009) and 4245 (2016) FSW were analyzed. Commercial sex debut shifted to younger ages: while in 2009 the proportion of women who started sex work under 18 years old was 28.3%, in 2016 this percentage rose to 38.3%. The proportion of FSW affiliated to a nongovernmental organization (NGO) in defense of their rights (14.0%), in 2009, decreased to 7.8%, in 2016, as well as the proportion of FSW who received counseling on sexually transmitted infections (STI) in the past 6 months, from 47.5% to 24.4%. Relevant improvements were found for HIV testing in the last 12 months (from 20.3% to 39.3%). The proportions of those who were never tested for syphilis dropped from 57.9% to 48.5%. However, an opposite decreasing trend was found for the Pap smear examination in the last 12 months, decreasing from 43.6% to 31.5%. Regular condom use with clients significantly increased in the period. Regarding HIV prevalence, the 5% level was sustained and no significant differences were found, but syphilis prevalence was found to be more than 3 times higher in 2016 (8.5%) than in 2009 (2.4%).Discussion:Many are the challenges to be faced in attempting to reverse the upward trend of syphilis among FSW in Brazil. Despite the progress in condom distribution free of charge, it is necessary to increase awareness campaigns, emphasize the use, reaffirm STI counseling, and reiterate the need of regular syphilis screening in this key population group.

HIV, HCV, HBV, and syphilis among transgender women from Brazil: Assessing different methods to adjust infection rates of a hard-to-reach, sparse population.

Different sampling strategies, analytic alternatives, and estimators have been proposed to better assess the characteristics of different hard-to-reach populations and their respective infection rates (as well as their sociodemographic characteristics, associated harms, and needs) in the context of studies based on respondent-driven sampling (RDS). Despite several methodological advances and hundreds of empirical studies implemented worldwide, some inchoate findings and methodological challenges remain. The in-depth assessment of the local structure of networks and the performance of the available estimators are particularly relevant when the target populations are sparse and highly stigmatized. In such populations, bottlenecks as well as other sources of biases (for instance, due to homophily and/or too sparse or fragmented groups of individuals) may be frequent, affecting the estimates.In the present study, data were derived from a cross-sectional, multicity RDS study, carried out in 12 Brazilian cities with transgender women (TGW). Overall, infection rates for HIV and syphilis were very high, with some variation between different cities. Notwithstanding, findings are of great concern, considering the fact that female TGW are not only very hard-to-reach but also face deeply-entrenched prejudice and have been out of the reach of most therapeutic and preventive programs and projects.We cross-compared findings adjusted using 2 estimators (the classic estimator usually known as estimator II, originally proposed by Volz and Heckathorn) and a brand new strategy to adjust data generated by RDS, partially based on Bayesian statistics, called for the sake of this paper, the RDS-B estimator. Adjusted prevalence was cross-compared with estimates generated by non-weighted analyses, using what has been called by us a naïve estimator or rough estimates.

Risk behavior score: a practical approach for assessing risk among men who have sex with men in Brazil

HIV/AIDS epidemic is not well controlled, and multiple sexual behavior factors help explain high rates of HIV infection among men who have sex with men (MSM). This article proposes to exam the use of a potential risk behavior score for HIV infection, based on the type and number of sexual partners, and condom use, and their associated factors in a sample of MSM in Brazil. A cross sectional RDS (Respondent Driven Sampling) study was performed among 3738 MSM aged 18+ years old from ten Brazilian cities. The risk behavior score was composed by the number of male partners and anal condom use in the last year with steady, casual, and commercial partners. Most participants were 25+ years old (58.1%), non-white (83.1%), and single (84.9%). Final weighted ordinal logistic model showed that age≤25 years old (p=0.037), homosexual or bisexual identity (p<0.001), sexual initiation before 15-year-old (p<0.001), having sex with men only in the last 12 months (p<0.001), frequent alcohol and illicit drug use (p<0.001), and use of local sites to meet sexual partners in the last month were independently associated with higher scores of risky behavior. Specific strategies should be developed aimed at the MSM population. Additionally, pre-exposed prophylaxis (Prep) should be considered for those at higher score as a strategy for reducing risk for HIV infection in this population.

Bisexual and Bidirectional: Assessing the Potential for HIV Bridging in Mozambique.

African men who have sex with men (MSM) frequently, and often concurrently, have female partners, raising concerns about HIV sexual bridging. We explored potential HIV transmission in Mozambique from and to female partners of MSM focusing on preferred anal sex role and circumcision status. Data collected in a respondent-driven sampling study of MSM in 2011 in Maputo and Beira. Men who had oral or anal sex with other men 12months prior completed a questionnaire and consented for HIV testing. Statistical analysis explored demographic/risk characteristics and associations among circumcision status, anal sex with men, sexual positions during anal sex with men and vaginal or anal sex with women. We identified 326 MSM in Maputo and 237 in Beira with both male and female partners 3months before the study. Of these, 20.8% in Maputo and 36.0% in Beira had any receptive anal sex with men 12months prior, including 895 unprotected sexual acts with males in Maputo and 692 in Beira. Uncircumcised and exclusively insertive males, 27.7% of the sample in Maputo and 33.6% in Beira, had the most unprotected sex with females: 1159 total acts in Maputo and 600 in Beira. Sexual bridging between MSM and women likely varies geographically and is probably bi-directional, occurring within a generalized epidemic where HIV prevalence is higher among reproductive-age women than MSM. Prevention strategies emphasizing correct and consistent condom use for all partners and circumcision for bisexual men should be considered.

Prevalence of Human Immunodeficiency Virus and Sexually Transmitted Infections Among Cisgender and Transgender Women Sex Workers in Greater Kuala Lumpur, Malaysia: Results From a Respondent-Driven Sampling Study.

Sex workers face a disproportionate burden of human immunodeficiency virus (HIV) and sexually transmitted infections (STI) worldwide. For cisgender women sex workers (CWSW), global HIV prevalence is over 10%, whereas transgender women sex workers (TWSW) face an HIV burden of 19% to 27%. We used respondent-driven sampling to recruit 492 sex workers, including CWSW (n = 299) and TWSW (n = 193) in Greater Kuala Lumpur, Malaysia. Participants completed an in-depth survey and were screened for HIV, syphilis, Chlamydia trachomatis, and Neisseria gonorrhoeae. Sample characteristics stratified by gender identity and interview site are presented. Bivariate analyses comparing CWSW and TWSW were conducted using independent samples t tests for continuous variables and χ tests for categorical variables. Pooled HIV prevalence was high (11.7%; 95% confidence interval [CI], 8.8-14.5), and was similar for CWSW (11.1%) and TWSW (12.4%). Rates of syphilis 25.5% (95% CI, 21.6-29.5), C. trachomatis (14.8%; 95% CI, 11.6-18.0) and N. gonorrhoeae (5.8%; 95% CI, 3.7-7.9) were also concerning. Both groups reported lifetime HIV testing (62.4%), but CWSW were less likely to have ever been HIV tested (54.5%) than TWSW (74.6%). Median time since last HIV test was 24 months. Previous screening for STI was low. Inconsistent condom use and drug use during sex work were not uncommon. High HIV and STI prevalence, coupled with infrequent HIV and STI screening, inconsistent condom use, and occupational drug use, underscore the need for expanded HIV and STI prevention, screening, and treatment efforts among CWSW and TWSW in Malaysia.

Social venue range and referral chain impact: Implications for the sampling of hidden communities.

BackgroundIt has been argued that the success of respondent-driven sampling (RDS) in generating unbiased estimates for epidemiologic outcomes depends on participants’ abilities to generate long referral chains. While this is thought to depend on the number of people participants know in the target population, this idea is rarely tested. Furthermore, little attention has been paid to the role of other aspects of social connectedness in recruitment, such as participants’ involvement in local clubs and venues.MethodsWe examine whether the recruitment potential of young Black men who have sex with men (YBMSM) depends on (1) their social network size and (2) their affiliations with a variety of sex venues across geographic areas. We analyze data from a 2014 RDS study of 598 YBMSM on the south side of Chicago.ResultsBoth a participant’s personal network size and the number of different types of sex venues with which he was affiliated were significantly positively associated with (1) the total number of recruits in the participant’s prospective referral chains and (2) the lengths of those chains. However, only venue affiliation remain significantly associated with recruitment potential in the multivariate model.ConclusionsThe success of RDS in generating valid samples may depend more on recruiting participants who are involved in multiple venues within the community (i.e., their affiliation networks) than on recruiting those who have large personal social networks.

Identification of Homophily and Preferential Recruitment in Respondent-Driven Sampling.

Respondent-driven sampling (RDS) is a link-tracing procedure used in epidemiologic research on hidden or hard-to-reach populations in which subjects recruit others via their social networks. Estimates from RDS studies may have poor statistical properties due to statistical dependence in sampled subjects' traits. Two distinct mechanisms account for dependence in an RDS study: homophily, the tendency for individuals to share social ties with others exhibiting similar characteristics, and preferential recruitment, in which recruiters do not recruit uniformly at random from their network alters. The different effects of network homophily and preferential recruitment in RDS studies have been a source of confusion and controversy in methodological and empirical research in epidemiology. In this work, we gave formal definitions of homophily and preferential recruitment and showed that neither is identified in typical RDS studies. We derived nonparametric identification regions for homophily and preferential recruitment and showed that these parameters were not identified unless the network took a degenerate form. The results indicated that claims of homophily or recruitment bias measured from empirical RDS studies may not be credible. We applied our identification results to a study involving both a network census and RDS on a population of injection drug users in Hartford, Connecticut (2012-2013).

Epidemiology of HIV and hepatitis C infection among women who inject drugs in Northeast India: a respondent-driven sampling study.

Despite extensive research on HIV and hepatitis C (HCV) among people who inject drugs (PWID), there remains a gap in knowledge on the burden among women who inject drugs and their unique contexts and risk factors. This analysis compares HIV and HCV prevalence in female and male PWID and estimates injection and sexual risk correlates of prevalent HIV and HCV infection among women in Northeast India. Cross-sectional sample accrued using respondent-driven sampling. Seven cities in Northeast India, 2013. A total of 6457 adult PWID. Participants completed an interviewer-administered survey. HIV infection was diagnosed on-site and HCV antibody testing was performed on stored specimens. HIV and HCV prevalence estimates were stratified by gender. Among women, the association of risk correlates with HIV and HCV were estimated using multi-level logistic regression models. A total of 796 (15.9%) of the PWID were women, of whom 52.9% [95% confidence interval (CI)=49.3-56.5%] were HIV-infected and 22.3% (CI=19.9-24.7%) were HCV-infected. HIV and HCV prevalence among men was 17.4% (CI=16.9-24.7%) and 30.4% (CI=31.2-32.0%), respectively. Among women, correlates of HIV were widowhood [adjusted odds ratio (aOR) versus currently married=4.03, CI=2.13-7.60] and a higher number of life-time sexual partners (aOR ≥8 versus none=3.08, CI=1.07-8.86). Correlates of HCV were longer injection duration (aOR per 10 years=1.70, CI=1.25-2.27), injecting only heroin and a combination of drugs (aOR versus pharmaceuticals only=5.63, CI=1.68-18.9 and aOR=2.58, CI=1.60-4.16, respectively), sharing needles/syringes (aOR=2.46, CI=1.29-4.56) and a larger PWID network (aOR ≥51 versus 1-5=4.17, CI=2.43-7.17). Women who inject drugs in Northeast India have a high HIV prevalence, which was more than double their hepatitis C (HCV) prevalence, an opposite pattern than is observed typically among male PWID. HIV infection is associated with sexual risk factors while injection-related behaviors appear to drive HCV infection.

Unveiling of HIV dynamics among transgender women: a respondent-driven sampling study in Rio de Janeiro, Brazil

The burden of HIV in transgender women (transwomen) in Brazil remains unknown. We aimed to estimate HIV prevalence among transwomen in Rio de Janeiro and to identify predictors of newly diagnosed HIV infections. We recruited transwomen from Rio de Janeiro, Brazil, by respondent-driven sampling. Eligibility criteria were self-identification as transwomen, being 18 years of age or older, living in Rio de Janeiro or its metropolitan area, and having a valid peer recruitment coupon. We recruited 12 seed participants from social movements and formative focus groups who then used peer recruitment coupons to refer subsequent peers to the study. We categorised participants as HIV negative, known HIV infected, or newly diagnosed as HIV infected. We assessed predictors of newly diagnosed HIV infections by comparing newly diagnosed with HIV-negative participants. We derived population estimates with the Respondent-Driven Sampling II estimator. Between Aug 1, 2015, and Jan 29, 2016, we enrolled 345 eligible transwomen. 29·1% (95% CI 23·2-35·4) of participants had no previous HIV testing (adjusted from 60 participants), 31·2% (18·8-43·6) had HIV infections (adjusted from 141 participants), and 7·0% (0·0-15·9) were newly diagnosed as HIV infected (adjusted from 40 participants). We diagnosed syphilis in 28·9% (18·0-39·8) of participants, rectal chlamydia in 14·6% (5·4-23·8), and gonorrhoea in 13·5% (3·2-23·8). Newly diagnosed HIV infections were associated with black race (odds ratio 22·8 [95% CI 2·9-178·9]; p=0·003), travesti (34·1 [5·8-200·2]; p=0·0001) or transsexual woman (41·3 [6·3-271·2]; p=0·0001) gender identity, history of sex work (30·7 [3·5-267·3]; p=0·002), and history of sniffing cocaine (4·4 [1·4-14·1]; p=0·01). Our results suggest that transwomen bear the largest burden of HIV among any population at risk in Brazil. The high proportion of HIV diagnosis among young participants points to the need for tailored long-term health-care and prevention services to curb the HIV epidemic and improve the quality of life of transwomen in Brazil. Brazilian Research Council, National Institute of Allergy and Infectious Diseases, Brazilian Sexually Transmitted Disease/AIDS, and Viral Hepatitis Department of the Brazilian Ministry of Health.

Prevalence and patterns of victimization and polyvictimization among female sex workers in Soweto, a South African township: a cross-sectional, respondent-driven sampling study

ABSTRACT Background: Female sex workers (FSWs) are disproportionately affected by violence from multiple partner categories. This increases their vulnerability to HIV. Objectives: To describe patterns of violence and polyvictimization among female SWs in Soweto. Methods: A respondent-driven sampling (RDS) recruitment methodology was used to enrol 508 Soweto-based FSWs using a survey instrument. Raw and RDS adjusted data were descriptively analysed, Spearman’s correlation and chi2 test of association were used to show associations. Polyvictimization patterns are shown within a modified Venn diagram. Results: The median age of FSWs in Soweto was 31 years, and most had an incomplete education (74.2%). The prevalence of exposure to physical/sexual intimate partner violence (IPV) in the past year was 53.8%, 46.8% by clients, and 18.5% by police. Past year prevalence of sexual/physical violence by any perpetrator category was 70.8% and lifetime exposure was 76.0%. Childhood sexual violence was reported by 44.3%. Lifetime non-partner rape was 55.5% and all rape exposure was 62.4%. As a result of engaging in sex work in the past year, 65.2% women had been discriminated against. Client, police, IPV, and childhood trauma were all significantly associated with one another, with IPV being the most common co-occurrence. Polyvictimization was seen in almost two-thirds of FSWs, and increased with exposure to discrimination. Conclusion: In Soweto, FSWs are exposed to high rates of violence in multiple forms across their lifetime. Our findings show that violence continues unabated into adulthood at levels far higher than in the general population and overall at higher levels than previously recorded among SWs in South Africa. We argue that violence against FSWs is rooted in discrimination. The disparate burden of violence on FSWs requires urgent interventions to proactively address and reframe the normalisation of violence against all women.

HIV testing and the care continuum among transgender women: population estimates from Rio de Janeiro, Brazil.

Introduction: Evidence suggests that, of all affected populations, transgender women (transwomen) may have the heaviest HIV burden worldwide. Little is known about HIV linkage and care outcomes for transwomen. We aimed to estimate population-level indicators of the HIV cascade of care continuum, and to evaluate factors associated with viral suppression among transwomen in Rio de Janeiro, Brazil. Methods: We conducted a respondent-driven sampling (RDS) study of transwomen from August 2015 to January 2016 in Rio de Janeiro, Brazil and collected data on linkage and access to care, antiretroviral treatment and performed HIV viral load testing. We derived population-based estimates of cascade indicators using sampling weights and conducted RDS-weighted logistic regression analyses to evaluate correlates of viral suppression (viral load ≤50 copies/mL). Results: Of the 345 transwomen included in the study, 89.2% (95% CI 55–100%) had been previously tested for HIV, 77.5% (95% CI 48.7–100%) had been previously diagnosed with HIV, 67.2% (95% CI 39.2–95.2) reported linkage to care, 62.2% (95% CI 35.4–88.9) were currently on ART and 35.4% (95% CI 9.5–61.4%) had an undetectable viral load. The final adjusted RDS-weighted logistic regression model for viral suppression indicated that those who self-identified as black (adjusted odds ratio [aOR] 0.06, 95% CI 0.01–0.53, p < 0.01), reported earning ≤U$160/month (aOR 0.11, 95% CI 0.16–0.87, p = 0.04) or reported unstable housing (aOR 0.08, 95% CI 0.01–0.43, p < 0.01) had significantly lower odds of viral suppression. Conclusions: Our cascade indicators for transwomen showed modest ART use and low viral suppression rates. Multi-level efforts including gender affirming care provision are urgently needed to decrease disparities in HIV clinical outcomes among transwomen and reduce secondary HIV transmission to their partners.