Clinic presentation delay and tuberculosis treatment outcomes in the Lake Victoria region of East Africa: A multi-site prospective cohort study.

In the Lake Victoria region of East Africa, little is known about delays between tuberculosis (TB) symptom onset and presentation at a clinic. Associations between clinic presentation delay and TB treatment outcomes are also poorly understood. In 2019, we abstracted data from routine TB treatment records for all adults (n = 776) initiating TB treatment in a 6-month period across 12 health facilities near Lake Victoria. We interviewed 301 cohort members and assessed whether they experienced a clinic presentation delay longer than 6 weeks. We investigated potential clinical and demographic correlates of clinic presentation delay and examined the association between clinic presentation delay and an unfavorable TB treatment outcome (death, loss to follow-up, or treatment failure). Clinic presentation delay was common, occurring among an estimated 54.7% (95% CI: 48.9%, 61.2%) of cohort members, though no specific correlates were identified. Clinic presentation delay was slightly associated with unfavorable TB treatment outcomes. The 180-day risk of an unfavorable outcome was 14.2% (95% CI: 8.0%, 20.4%) among those with clinic presentation delay, compared to 12.7% (95% CI: 5.1%, 20.3%) among those presenting earlier. Multi-level community-based interventions may be necessary to reduce clinic presentation delays in communities near Lake Victoria.

Geographic mobility and treatment outcomes among people in care for tuberculosis in the Lake Victoria region of East Africa: A multi-site prospective cohort study.

Geographic mobility may disrupt continuity of care and contribute to poor clinical outcomes among people receiving treatment for tuberculosis (TB). This may occur especially where health services are not well coordinated across international borders, particularly in lower and middle income country settings. In this work, we describe mobility and the relationship between mobility and unfavorable TB treatment outcomes (i.e., death, loss to follow-up, or treatment failure) among a cohort of adults who initiated TB treatment at one of 12 health facilities near Lake Victoria. We abstracted data from health facility records for all 776 adults initiating TB treatment during a 6-month period at the selected facilities in Kenya, Tanzania, and Uganda. We interviewed 301 cohort members to assess overnight travel outside one's residential district/sub-county. In our analyses, we estimated the proportion of cohort members traveling in 2 and 6 months following initiation of TB treatment, explored correlates of mobility, and examined the association between mobility and an unfavorable TB treatment outcome. We estimated that 40.7% (95% CI: 33.3%, 49.6%) of people on treatment for TB traveled overnight at least once in the 6 months following treatment initiation. Mobility was more common among people who worked in the fishing industry and among those with extra-pulmonary TB. Mobility was not strongly associated with other characteristics examined, however, suggesting that efforts to improve TB care for mobile populations should be broad ranging. We found that in this cohort, people who were mobile were not at increased risk of an unfavorable TB treatment outcome. Findings from this study can help inform development and implementation of mobility-competent health services for people with TB in East Africa.

Differences in Access to HIV Services and Risky Sexual Behaviors Among Malawian Women at Social Venues Who Do and Do Not Engage in Sex Work.

In the high HIV-burden country of Malawi, female sex workers (FSW) are one of the populations most profoundly affected by HIV. The Malawi Priorities for Local AIDS Control Efforts (PLACE) surveyed 1,004 self-identified FSW, 213 other FSW (OFSW), and 130 other high risk women (OHRW) at social venues. Analyses compared the three groups using survey-weighted log binomial regression models. Each group had a distinct pattern of usage and access to services: OFSW and FSW had greater access to condoms, while using a condom ever was greatest among FSW. Nearly all women knew where to get tested for HIV but very few used FSW drop-in centers. HIV prevalence was high in all three groups (35% FSW, 20% OFSW, 20% OHRW). Given these results, HIV services should be targeted to all women at social venues in Malawi, regardless of sex worker status to improve health outcomes and limit onward transmission of HIV.

Improving HIV outreach testing yield at cross-border venues in East Africa.

OBJECTIVE: The aim of this study was to evaluate HIV testing yield under several candidate strategies for outreach testing at venues (i.e. places where people socialize and meet new sex partners) in East Africa cross-border areas. DESIGN: Population-based cross-sectional biobehavioural survey of people who had not been previously diagnosed with HIV found in venues. METHODS: We identified participants who would have been tested for HIV under each of 10 hypothetical outreach testing strategies and calculated the proportion who would have newly tested positive for HIV under each strategy. On the basis of this proportion, we calculated the 'number needed to test' (NNT) to identify one new case of HIV under each strategy. All estimates were obtained by applying survey sampling weights to account for the complex sampling design. RESULTS: If testing was performed at a random sample of venues, 35 people would need to be tested to identify one new case of HIV, but higher yield could be found by limiting testing to venues with specific characteristics. Strategies focusing on women had higher testing yield. Testing women employed by venues would result in highest yield of all strategies examined (NNT = 15), while testing men under age 24 would result in the lowest yield (NNT = 99). CONCLUSION: Quantitatively evaluating HIV testing strategies prior to implementation using survey data presents a new opportunity to refine and prioritize outreach testing strategies for the people and places most likely to result in high HIV testing yield.

Sex work, discrimination, drug use and violence: a pattern for HIV risk among transgender sex workers compared to MSM sex workers and other MSM in Guatemala.

The risk of HIV infection is higher among transgender women and cisgender men who have sex with men (MSM) compared to the general population due in part to social and contextual factors. This study aimed to determine the prevalence and association of alcohol and drug abuse, discrimination and violence among transgender sex workers compared to cisgender male sex workers and cisgender men who had not received money for sex in Guatemala City. In 2010, transgender women and cisgender men who had had sex with men or transgender women were recruited into a cross-sectional behavioural survey. Among transgender women, 86% received money for sex in the past year. Transgender sex workers were more likely to use drugs and binge drink, three times as likely to be discriminated against and eight times as likely to be forced to have sex compared to non-sex worker men. Male sex workers were twice as likely to use illicit drugs or experience physical violence and six times as likely to experience forced sex compared to non-sex worker men. Transgender and male sex workers would benefit from harm reduction for substance use, violence prevention, response and strategies to mitigate discrimination.

The burden of HIV among female sex workers, men who have sex with men and transgender women in Haiti: results from the 2016 Priorities for Local AIDS Control Efforts (PLACE) study.

INTRODUCTION: Despite the higher risk of HIV among female sex workers (FSWs), men who have sex with men (MSM) and transgender women (TGW), these populations are under-represented in the literature on HIV in Haiti. Here, we present the first nationally representative estimates of HIV prevalence and the first care and treatment cascade for FSWs, MSM and TGW in Haiti. We also examine the social determinants of HIV prevalence in these groups and estimate FSW and MSM population size in Haiti. METHODS: Data were collected between April 2016 and February 2017 throughout the 10 geographical departments of Haiti. The Priorities for Local AIDS Control Efforts (PLACE) method was used to: (1) recruit participants for a behavioural survey; (2) provide rapid testing, counselling and linkage to care for syphilis and HIV; and (3) measure viral load using dried blood spots for participants testing HIV positive. RESULTS: Study participants included 990 FSWs, 520 MSM and 109 TGW. HIV prevalence was estimated at 7.7% (95% CI 6.2%, 9.6%) among FSWs, 2.2% (0.9%, 5.3%) among MSM and 27.6% (5.0%, 73.5%) among TGW. Of participants who tested positive for syphilis, 17% of FSWs, 19% of MSM and 74% of TGW were co-infected with HIV. Economic instability and intimate partner violence (IPV) were significantly associated with HIV among MSM; food insecurity, economic instability and history of rape were significantly associated with HIV among TGW. Fewer than one-third of participants living with HIV knew their status, and more than a quarter of those who knew their status were not on treatment. While approximately four in five FSW and MSM participants on treatment for HIV were virally suppressed, viral suppression was less common among TGW participants at only 46%. CONCLUSIONS: This study demonstrates a need for targeted interventions to prevent and treat HIV among key populations in Haiti. Potential high-impact interventions may include venue-based, peer navigator-led outreach and testing for HIV and syphilis and improving screening and case management for structural violence and IPV. TGW are in urgent need of such interventions due to our observations of alarmingly high HIV prevalence and low frequency of HIV viral suppression among TGW.

Programmatic Mapping: Providing Evidence for High Impact HIV Prevention Programs for Female Sex Workers.

Programmatic mapping (PM) is a rapid and efficient mechanism to develop size estimates of key populations including female sex workers (FSWs) and geolocate them at physical locations in a systematic and scientific manner. At the macro level, this information forms the basis for allocating program resources, setting performance targets, and assess coverage. At a micro level, PM data provide specific information on hot spots, estimates of FSWs at those spots, and hot spot typology and days and times of operation, all of which provides targeted service delivery strategies. This information can provide a reliable platform to plan HIV prevention and treatment services to considerable scale and intensity. Above all, the entire PM process requires deep involvement of FSWs, which increases community ownership of the data and can lead to an increased uptake of services. Despite a few limitations, the approach is versatile and can be used in varied country contexts to generate important information about sex work and its dynamics. In this paper, we describe experiences and lessons learned from using evidence generated from PM of FSWs in multiple countries to develop HIV prevention programs at scale.

How Can Programs Better Support Female Sex Workers to Avoid HIV Infection in Zimbabwe? A Prevention Cascade Analysis.

BACKGROUND: "HIV prevention cascades" have been proposed to support programs by identifying gaps in demand for, access to, and capability to adhere to HIV prevention tools, but there are few empirical examples to guide development. We apply a prevention cascade framework to examine prevention coverage and factors associated with condoms and/or PrEP adherence among female sex workers. SETTING: Seven sites across Zimbabwe. METHODS: Seven respondent-driven sampling surveys from the intervention sites of a pragmatic cluster-randomized trial in Zimbabwe in 2016 were analyzed, and 611/1439 women testing HIV-negative included. We operationalized key components of an HIV prevention cascade including demand, supply, and capability to adhere to 2 tools for HIV prevention: condoms and pre-exposure prophylaxis (PrEP). We used adjusted logistic regression to identify determinants of adherence to condoms and PrEP in turn, examining the effect of adherence to one tool on adherence to the other. RESULTS: There were 343/611, 54.7%, women reporting adherence to condoms and/or PrEP, leaving almost half uncovered. Although women were aware that condoms prevented HIV and reported good access to them, only 45·5% reported full adherence to condom use. For PrEP, a new technology, there were gaps along all 3 domains of demand, supply, and adherence. Alcohol use decreased adherence to PrEP and condoms. Younger and newer entrants to sex work were less likely to take PrEP every day. CONCLUSIONS: HIV prevention programming among female sex workers in Zimbabwe could consider increasing awareness of PrEP alongside supply, alcohol use interventions, and approaches to engaging younger women.

Reaching key populations through key venues: Insights from the Jamaica HIV Prevention Program.

INTRODUCTION: HIV prevention strategies often include outreach to female sex workers at social venues identified as places where people meet new sexual partners. Patrons and staff at these venues may include female sex workers, their clients, as well as others who have high rates of new sexual partnerships. Few studies have compared HIV/STI among venue-based and general populations, across types of venues, or by sub-group of the venue population. Program planners often assume that the prevalence of infection is highest among female sex workers and considerably lower among other people at these venues, but there are few empiric studies assessing the prevalence of infection by sex worker status and type of venue. METHODS: In 2011, we used the PLACE method to identify public venues where people meet new sexual partners across Jamaica. The study team visited all venues with reported sex work as well as a 10% random sample of other venues and subsequently interviewed and tested a probability sample of 991 venue patrons and workers for HIV and other STI. RESULTS: Community informants identified 1207 venues. All venues where sex work was reported (735 venues) and a random sample of the remainder (134 of 472) were selected for onsite visits. Of these, 585 were found and operational. At a stratified random sample of venues, survey teams interviewed and tested 717 women and 274 men. 394 women reported recent sex work and 211 of these women reported soliciting clients on the street. Women exchanging sex for money were more likely to be infected with HIV (5.4% vs 1.0%; OR = 5.6, 95% CI = 1.8,17.3) or syphilis (11.7% vs. 5.8%, OR = 2.2, 95% CI = 1.7,4,0) than other women, but not significantly more likely to be infected with gonorrhea (8.4% vs 7.8%; OR = 1.1,95% CI = 0.6,1.9), chlamydia (16.2% vs 21.6%;OR = 0.7,95% CI = 0.5,1.0) or trichomoniasis (23.0% vs 17.0%, OR = 1.5,95% CI = 0.9,2.2). Women at venues were more likely to report sex work and multiple partners than women interviewed in a 2008 national population-based household survey commissioned by the Ministry of Health. CONCLUSIONS: In Jamaica, although the highest HIV prevalence was among street-based sex workers, the risk of HIV and STI extends to men and women at high risk venues, even those who do not self-identify as sex workers. Findings confirm the appropriateness of outreach to all men and women at these venues.

Estimating Sizes of Key Populations at the National Level: Considerations for Study Design and Analysis.

BACKGROUND: National estimates of the sizes of key populations, including female sex workers, men who have sex with men, and transgender women are critical to inform national and international responses to the HIV pandemic. However, epidemiologic studies typically provide size estimates for only limited high priority geographic areas. This article illustrates a two-stage approach to obtain a national key population size estimate in the Dominican Republic using available estimates and publicly available contextual information. METHODS: Available estimates of key population size in priority areas were augmented with targeted additional data collection in other areas. To combine information from data collected at each stage, we used statistical methods for handling missing data, including inverse probability weights, multiple imputation, and augmented inverse probability weights. RESULTS: Using the augmented inverse probability weighting approach, which provides some protection against parametric model misspecification, we estimated that 3.7% (95% CI = 2.9, 4.7) of the total population of women in the Dominican Republic between the ages of 15 and 49 years were engaged in sex work, 1.2% (95% CI = 1.1, 1.3) of men aged 15-49 had sex with other men, and 0.19% (95% CI = 0.17, 0.21) of people assigned the male sex at birth were transgender. CONCLUSIONS: Viewing the size estimation of key populations as a missing data problem provides a framework for articulating and evaluating the assumptions necessary to obtain a national size estimate. In addition, this paradigm allows use of methods for missing data familiar to epidemiologists.

Achieving the first 90 for key populations in sub-Saharan Africa through venue-based outreach: challenges and opportunities for HIV prevention based on PLACE study findings from Malawi and Angola.

INTRODUCTION: Providing outreach HIV prevention services at venues (i.e. "hotspots") where people meet new sex partners can decrease barriers to HIV testing services (HTS) for key populations (KP) in sub-Saharan Africa (SSA). We offered venue-based HTS as part of bio-behavioural surveys conducted in urban Malawi and Angola to generate regional insights into KP programming gaps and identify opportunities to achieve the "first 90" for KP in SSA. METHODS: From October 2016 to March 2017, we identified and verified 1054 venues in Luanda and Benguela, Angola and Zomba, Malawi and conducted bio-behavioural surveys at 166 using the PLACE method. PLACE interviews community informants to systematically identify public venues where KP can be reached and conducts bio-behavioural surveys at a stratified random sample of venues. We present survey results using summary statistics and multivariable modified Poisson regression modelling to examine associations between receipt of outreach worker-delivered HIV/AIDS education and HTS uptake. We applied sampling weights to estimate numbers of HIV-positive KP unaware of their status at venues. RESULTS: We surveyed 959 female sex workers (FSW), 836 men who have sex with men (MSM), and 129 transgender women (TGW). An estimated 71% of HIV-positive KP surveyed were not previously aware of their HIV status, receiving a new HIV diagnosis through PLACE venue-based HTS. If venue-based HTS were implemented at all venues, 2022 HIV-positive KP (95% CI: 1649 to 2477) who do not know their status could be reached, including 1666 FSW (95% CI: 1397 to 1987), 274 MSM (95% CI: 160 to 374), and 82 TG (95% CI: 20 to 197). In multivariable analyses, FSW, MSM, and TGW who received outreach worker-delivered HIV/AIDS education were 3.15 (95% CI: 1.99 to 5.01), 3.12 (95% CI: 2.17 to 4.48), and 1.80 (95% CI: 0.67 to 4.87) times as likely, respectively, as those who did not to have undergone HTS within the last six months. Among verified venues, <=68% offered any on-site HIV prevention services. CONCLUSIONS: Availability of HTS and other HIV prevention services was limited at venues. HIV prevention can be delivered at venues, which can increase HTS uptake and HIV diagnosis among individuals not previously aware of their status. Delivering venue-based HTS may represent an effective strategy to reach the "first 90" for KP in SSA.

The role of venues in structuring HIV, sexually transmitted infections, and risk networks among men who have sex with men.

BACKGROUND: Venues form part of the sampling frame for time-location sampling, an approach often used for HIV surveillance. While sampling location is often regarded as a nuisance factor, venues may play a central role in structuring risk networks. We investigated individual reports of risk behaviors and infections among men who have sex with men (MSM) attending different venues to examine structuring of HIV risk behaviors. However, teasing apart 'risky people' from 'risky places' is difficult, as individuals cannot be randomized to attend different venues. However, we can emulate this statistically using marginal structural models, which inversely weight individuals according to their estimated probability of attending the venue. METHODS: We conducted a cross-sectional survey of 609 MSM patrons of 14 bars in San Diego, California, recruited using the Priorities for Local AIDS Control Efforts (PLACE) methodology, which consists of a multi-level identification and assessment of venues for HIV risk through population surveys. RESULTS AND DISCUSSION: Venues differed by many factors, including participants' reported age, ethnicity, number of lifetime male partners, past sexually transmitted infection (STI), and HIV status. In multivariable marginal structural models, venues demonstrated structuring of HIV+ status, past STI, and methamphetamine use, independently of individual-level characteristics. CONCLUSIONS: Studies using time-location sampling should consider venue as an important covariate, and the use of marginal structural models may help to identify risky venues. This may assist in widespread, economically feasible and sustainable targeted surveillance and prevention. A more mechanistic understanding of how 'risky venues' emerge and structure risk is needed.

The Where and How for Reaching Transgender Women and Men Who Have Sex with Men with HIV Prevention Services in Guatemala.

This study aims to describe the transgender women and men who have sex with men (MSM) missed through venue-based sampling and illustrate how data on venues can be used to prioritize service delivery. Respondent-driven sampling (RDS) and time-location sampling (TLS) were used concurrently in 2010 for behavioral surveillance among MSM and transgender women in Guatemala City. RDS recruits who did not frequent venues (n = 106) were compared to TLS recruits (n = 609). TLS participants recruited at different types of venues were compared. RDS recruits who did not frequent venues were less educated, less likely to identify as gay, more likely to have concurrent partners and female sexual partners. Participants recruited at NGOs, saunas, hotels, streets and parks had more partners, were more likely to receive money for sex or have concurrent partners. Prevention programs for MSM and transgender women should characterize social venues and people that frequent them and improve service coverage through venues and social networks.

HIV Drug Resistance Surveillance Among Jamaican Men Who Have Sex with Men Should Be Prioritized for Reducing HIV Transmission.

The prevalence of human immunodeficiency virus type 1 (HIV-1) is highest among men who have sex with men (MSM) in Jamaica but no genotypic data are available on the virus strains that are responsible for the epidemic among this key population. HIV-1 polymerase (pol) genes from 65 MSM were sequenced and used to predict drug resistance mutations. An HIV drug resistance prevalence of 28% (minimum 13%) was observed among this cohort, with the most frequent mutations conferring resistance to efavirenz, nevirapine, and lamivudine. Phylogenetic analysis of the sequences revealed 10 times the number of linked HIV infections among this cohort than respondent reporting. HIV treatment and prevention efforts in Jamaica could benefit significantly from Pol genotyping of the HIV strains infecting socially vulnerable MSM prior to initiating antiretroviral therapy (ART), as this would guide suppressive ART and unearth HIV transmission clusters to enable more effective delivery of treatment and prevention programs.

Understanding the high prevalence of HIV and other sexually transmitted infections among socio-economically vulnerable men who have sex with men in Jamaica.

OBJECTIVES: This study estimates HIV prevalence among men who have sex with men (MSM) in Jamaica and explores social determinants of HIV infection among MSM. DESIGN: An island-wide cross-sectional survey of MSM recruited by peer referral and outreach was conducted in 2011. A structured questionnaire was administered and HIV/STI tests done. We compared three groups: MSM who accepted cash for sex within the past 3 months (MSM SW), MSM who did not accept cash for sex (MSM non-SW), and MSM with adverse life events (ever raped, jailed, homeless, victim of violence or low literacy). RESULTS: HIV prevalence among 449 MSM was 31.4%, MSM SW 41.1%, MSM with adverse life events 38.5%, 17 transgender MSM (52.9%), and MSM non-SW without adverse events 21.0%. HIV prevalence increased with age and number of adverse life events (test for trend P < 0.001), as did STI prevalence (P = 0.03). HIV incidence was 6.7 cases/100 person-years (95% CI: 3.74, 12.19). HIV prevalence was highest among MSM reporting high-risk sex; MSM SW who had been raped (65.0%), had a STI (61.2%) and who self identified as female (55.6%). Significant risk factors for HIV infection common to all 3 subgroups were participation in both receptive and insertive anal intercourse, high-risk sex, and history of a STI. Perception of no or little risk, always using a condom, and being bisexual were protective. CONCLUSION: HIV prevalence was high among MSM SW and MSM with adverse life events. Given the characteristics of the sample, HIV prevalence among MSM in Jamaica is probably in the range of 20%. The study illustrates the importance of social vulnerability in driving the HIV epidemic. Programs to empower young MSM, reduce social vulnerability and other structural barriers including stigma and discrimination against MSM are critical to reduce HIV transmission.

"Do you think your main partner has other sex partners?" A simple question provides insight into sexual risk in Jamaica.

To estimate the association between a simple measure of sexual partner concurrency and sexually transmitted infection (STI) we conducted a cross-sectional population-based household survey (n = 1795) and targeted surveys of people at venues where people meet sexual partners (n = 1580) to ask about sexual behaviour. Persons interviewed at venues were tested for HIV, gonorrhoea, chlamydia, and trichomoniasis. We compared the association between STI and reporting a partner had other partners. More women than men reported their main partner had other partners. Thirteen percent of all women in the population-based survey and 14.4% in the targeted survey reported having one partner in the past 12 months and that partner had additional partners. STI prevalence was significantly associated with reporting a partner had other partners (36.8% vs. 30.2%; prevalence ratio [PR] 1.2; 95% confidence interval [CI] 1.1, 1.4). Construction of complete sexual networks is costly and not routinely feasible. We recommend adding a question to cross-sectional surveys used to monitor sexual behaviour about whether the respondent believes his or her partner has other sexual partners. Although subject to bias, the question was useful in Jamaica to identify a group of women with only one sexual partner at increased risk of infection.

Brief non-commercial sexual encounters among patrons of entertainment venues in Liuzhou, China.

Brief non-commercial sexual encounters among patrons of social venues are increasing in China, but whether these encounters increase syphilis risk is unknown. We surveyed and tested 797 men and women at randomly selected social venues in urban Liuzhou and three surrounding counties. The percent reporting recent non-commercial one-time sex ranged from 14.5% of county women to 24.8% of urban men. 2.4% of men and 3.7% of women had a positive rapid syphilis test. Men reporting non-commercial one-time sex were significantly more likely to have a positive rapid syphilis test than other men (7.4 vs. 0.9%). Among women, commercial sex was more strongly associated with syphilis than non-commercial one-time sex (6.0 vs. 0.7%). Recent one-time sex was common and associated with syphilis among men. Venue-based HIV/STI prevention methods may be warranted among persons who do not engage in commercial sex, but frequently engage in one-time sex.

Exploring venue-associated risk: a comparison of multiple partnerships and syphilis infection among women working at entertainment and service venues.

The re-emerging syphilis epidemic in China is documented among sex workers, but little is known about STI risk among the broader group of women who work at entertainment and service venues, many of whom do not self-identify as sex workers. In 2009 in Liuzhou, China, community informants identified venues where people meet sexual partners. Characteristics of a stratified random sample of venues were collected during venue visits. Female staff at 42 venues were interviewed and tested for syphilis. The results showed that venue characteristics, worker behaviors, and syphilis prevalence differed by venue type. Service venue workers had more sexual partners, were more likely to report sex work, and more likely to have a positive syphilis test than entertainment venue workers (prevalence ratio: 5.4; 95% CI 1.4-20.6). To conclude, risk of syphilis differs by venue type and is higher at service venues, even among women who do not report commercial sex.

From coitus to concurrency: sexual partnership characteristics and risk behaviors of 15-19 year old men recruited from urban venues in Tanzania.

Understanding the uptake and patterns of sexual partnerships of adolescent males reveals their risky behaviors that could persist into adulthood. Using venue-based sampling, we surveyed 671 male youth ages 15-19 from an urban Tanzanian neighborhood about their sexual partnerships during the past 6 months. The proportion of males who had ever had sex increased with age (21 % at age 15; 70 % at age 17; 94 % at age 19), as did the proportion who engaged in concurrency (5 % at age 15; 28 % at age 17; 44 % at age 19). Attendance at ≥2 social venues per day and meeting a sexual partner at a venue was associated with concurrency. Concurrency was associated with alcohol consumption before sex among 18-19 year olds and with not being in school among 15-17 year olds. We find that concurrency becomes normative over male adolescence. Venue-based sampling may reach youth vulnerable to developing risky sexual partnership patterns.

A comparison of respondent-driven and venue-based sampling of female sex workers in Liuzhou, China.

OBJECTIVES: To compare two methods for sampling female sex workers (FSWs) for bio-behavioural surveillance. We compared the populations of sex workers recruited by the venue-based Priorities for Local AIDS Control Efforts (PLACE) method and a concurrently implemented network-based sampling method, respondent-driven sampling (RDS), in Liuzhou, China. METHODS: For the PLACE protocol, all female workers at a stratified random sample of venues identified as places where people meet new sexual partners were interviewed and tested for syphilis. Female workers who reported sex work in the past 4 weeks were categorised as FSWs. RDS used peer recruitment and chain referral to obtain a sample of FSWs. Data were collected between October 2009 and January 2010. We compared the socio-demographic characteristics and the percentage with a positive syphilis test of FSWs recruited by PLACE and RDS. RESULTS: The prevalence of a positive syphilis test was 24% among FSWs recruited by PLACE and 8.5% among those recruited by RDS and tested (prevalence ratio 3.3; 95% CI 1.5 to 7.2). Socio-demographic characteristics (age, residence and monthly income) also varied by sampling method. PLACE recruited fewer FSWs than RDS (161 vs 583), was more labour-intensive and had difficulty gaining access to some venues. RDS was more likely to recruit from areas near the RDS office and from large low prevalence entertainment venues. CONCLUSIONS: Surveillance protocols using different sampling methods can obtain different estimates of prevalence and population characteristics. Venue-based and network-based methods each have strengths and limitations reflecting differences in design and assumptions. We recommend that more research be conducted on measuring bias in bio-behavioural surveillance.