Does size really matter? A sensitivity analysis of number of seeds in a respondent-driven sampling study of gay, bisexual and other men who have sex with men in Vancouver, Canada

Evaluation of respondent-driven sampling in seven studies of people who use drugs from rural populations: findings from the Rural Opioid Initiative

BACKGROUND

Accurate prevalence estimates of drug use and its harms are important to characterize burden and develop interventions to reduce negative health outcomes and disparities. Lack of a sampling frame for marginalized/stigmatized populations, including persons who use drugs (PWUD) in rural settings, makes this challenging. Respondent-driven sampling (RDS) is frequently used to recruit PWUD. However, the validity of RDS-generated population-level prevalence estimates relies on assumptions that should be evaluated.

METHODS

RDS was used to recruit PWUD across seven Rural Opioid Initiative studies between 2018-2020. To evaluate RDS assumptions, we computed recruitment homophily and design effects, generated convergence and bottleneck plots, and tested for recruitment and degree differences. We compared sample proportions with three RDS-adjusted estimators (two variations of RDS-I and RDS-II) for five variables of interest (past 30-day use of heroin, fentanyl, and methamphetamine; past 6-month homelessness; and being positive for hepatitis C virus (HCV) antibody) using linear regression with robust confidence intervals. We compared regression estimates for the associations between HCV positive antibody status and (a) heroin use, (b) fentanyl use, and (c) age using RDS-1 and RDS-II probability weights and no weights using logistic and modified Poisson regression and random-effects meta-analyses.

RESULTS

Among 2,842 PWUD, median age was 34 years and 43% were female. Most participants (54%) reported opioids as their drug of choice, however regional differences were present (e.g., methamphetamine range: 4-52%). Many recruitment chains were not long enough to achieve sample equilibrium. Recruitment homophily was present for some variables. Differences with respect to recruitment and degree varied across studies. Prevalence estimates varied only slightly with different RDS weighting approaches, most confidence intervals overlapped. Variations in measures of association varied little based on weighting approach.

CONCLUSIONS

RDS was a useful recruitment tool for PWUD in rural settings. However, several violations of key RDS assumptions were observed which slightly impacts estimation of proportion although not associations.

Implementation of web-based respondent driven sampling in epidemiological studies

BACKGROUND

Respondent-driven sampling (RDS) is a peer chain-recruitment method for populations without a sampling frame or that are hard-to-reach. Although RDS is usually done face-to-face, the online version (WebRDS) has drawn a lot of attention as it has many potential benefits, despite this, to date there is no clear framework for its implementation. This article aims to provide guidance for researchers who want to recruit through a WebRDS.

METHODS

Description of the development phase: guidance is provided addressing aspects related to the formative research, the design of the questionnaire, the implementation of the coupon system using a free software and the diffusion plan, using as an example a web-based cross-sectional study conducted in Spain between April and June 2022 describing the working conditions and health status of homecare workers for dependent people.

RESULTS

The application of the survey: we discuss about the monitoring strategies throughout the recruitment process and potential problems along with proposed solutions.

CONCLUSIONS

Under certain conditions, it is possible to obtain a sample with recruitment performance similar to that of other RDS without the need for monetary incentives and using a free access software, considerably reducing costs and allowing its use to be extended to other research groups.

Examining differential success in recruitment using respondent driven sampling (RDS) in a multi-site study of gay, bisexual and other men who have sex with men

BACKGROUND

The Engage Study is a longitudinal biobehavioral cohort study of gay, bisexual and other men who have sex with men (GBM) in Toronto, Montreal, and Vancouver. Baseline data (2,449 participants) were collected from February 2017 - August 2019 using respondent-driven sampling (RDS). Recruitment in Montreal required fewer seeds, had a much shorter recruitment period, and recruited the largest sample.

METHODS

To better understand why RDS recruitment was more successful in Montreal compared to other sites, we conducted an analysis to examine RDS recruitment characteristics for GBM in each of the three study sites, explore demographic characteristics and measures of homophily, that is, the tendency of individuals to recruit other study participants who are like themselves, and compared motivations for study participation.

RESULTS

Montreal had the greatest proportion of participants over the age of 45 (29.1% in Montreal, 24.6% in Vancouver, and 21.0% in Toronto) and the highest homophily for this age group, but homophily was high across the three cities. Montreal also reported the lowest percentage of participants with an annual income greater or equal to $60,000 (7.9% in Montreal, 13.1% in Vancouver and 10.6% in Toronto), but homophily was similar across all three cities. The majority of participants indicated interest in sexual health and HIV as the main reason for participating (36.1% in Montreal, 34.7% in Vancouver, and 29.8% in Toronto). Financial interest as the main reason for participation was low (12.7% in Montreal, 10.6% in Vancouver, and 5.7% in Toronto).

CONCLUSION

Taken together, although we found some differences in study demographic characteristics and homophily scores, we were unable to fully explain the different recruitment success based on the data available. Our study underlines the fact that success of RDS implementation may vary by unknown factors, and that researchers should be proactive and flexible to account for variability.

Nominal Versus Realized Costs of Recruiting and Retaining a National Sample of Sexual Minority Adolescents in the United States: Longitudinal Study

BACKGROUND

Web-based recruitment for research studies is becoming increasingly popular and necessary. When compared with the traditional methods of recruitment, these methods may enable researchers to reach more diverse participants in less time. Social media use is highly prevalent among adolescents, and the unique context of social media may be particularly important for the recruitment of sexual minority young people who would not be captured by traditional methods.

OBJECTIVE

This paper described the details of a national web-based study recruitment approach aimed at sexual minority adolescents across the United States, focusing on important details of this relatively novel approach, including cost, time efficiency, and retention outcomes.

METHODS

This study recruited sexual minority adolescents aged 14-17 years living in the United States through targeted advertisements on Facebook, Instagram, and YouTube and through respondent-driven sampling (RDS). Potential participants completed eligibility screening surveys and were automatically directed to a baseline survey if they were eligible. After baseline survey completion, additional data checks were implemented, and the remaining participants were contacted for recruitment into a longitudinal study (surveys every 6 months for 3 years).

RESULTS

Recruitment lasted 44 weeks, and 9843 participants accessed the initial screening survey, with 2732 (27.76%) meeting the eligibility criteria and completing the baseline survey. Of those, 2558 (93.63%) were determined to have provided nonfraudulent, usable study data and 1076 (39.39%) subsequently enrolled in the longitudinal study. Of the baseline sample, 79.05% (2022/2558) was recruited through Facebook and Instagram, 3.05% (78/2558) through YouTube, and 17.9% (458/2558) through RDS. The average cost of recruiting a participant into the study was US $12.98, but the recruitment cost varied by method or platform, with a realized cost of US $13 per participant on Facebook and Instagram, US $24 on YouTube, and US $10 through RDS. Participant differences (sex assigned at birth, race and ethnicity, sexual orientation, region, and urbanicity) were identified between platforms and methods both in terms of overall number of participants and cost per participant. Facebook and Instagram were the most time efficient (approximately 15 days to recruit 100 participants), whereas RDS was the least time efficient (approximately 70 days to recruit 100 participants). Participants recruited through YouTube were the most likely to be longitudinally retained, followed by Facebook and Instagram, and then RDS.

CONCLUSIONS

Large differences exist in study recruitment cost and efficiency when using social media and RDS. Demographic, region, and urbanicity differences in recruitment methods highlight the need for attention to demographic diversity when planning and implementing recruitment across platforms. Finally, it is more cost-effective to retain than recruit samples, and this study provided evidence that with thorough screening and data quality practices, social media recruitment can result in diverse, highly involved study populations.

Application of Bayesian networks to identify factors influencing acceptability of HIV pre-exposure prophylaxis in Guilin, China

Pre-exposure prophylaxis (PrEP) is an effective strategy to prevent uninfected individuals from contracting human immunodeficiency virus (HIV), however it must be acceptable to stakeholders in order to be effective. This study aimed to assess the acceptability of PrEP and related influencing factors. A cross-sectional survey was conducted among female sex workers (FSW), people who inject drugs (PWID), and men who have sex with men (MSM) using respondent driven sampling. Factors influencing PrEP acceptability were estimated using ordinal logistic regression and Bayesian networks. The survey included 765 eligible participants. The mean score of the perceived acceptability index was 3.9 (SD = 1.97). Multivariable logistic regression analysis revealed a higher acceptance of PrEP was associated with elder age, having other medical insurance, higher perceived utility of PrEP in facilitating prevention of HIV, higher perceived ease of use, higher perceived risk of increased risk behavior, higher perceived privacy problem in using PrEP, higher perceived comparative advantage over condom use, higher perceived comparative advantage of having sex when the urge arises, and higher perceived image of PrEP user as having sexual risky behavior, as public-minded and as health-conscious. The Bayesian network model showed perceived ease of use, perceived image of user as health-conscious, and perceived comparative advantage of having sex when the urge arises were directly associated with acceptability of PrEP. If these three factors were at a high level, 74.6% of the participants would have a high level of acceptability of PrEP. Effective education strategies to promote the acceptance of PrEP are needed. Implementation strategies should incorporate more inclusive messaging and build positive publicity for PrEP to reduce the stigma that PrEP use indicates risky behavior.

Virological suppression among gay, bisexual, and other men who have sex with men living with HIV in Vancouver, Canada: A longitudinal cohort study from 2012-2017

INTRODUCTION

In 2010, British Columbia (BC) implemented HIV Treatment as Prevention (TasP) as policy. We examined trends in virologic suppression and determinants of significant viremia among a prospective biobehavioural cohort of men who have sex with men (gbMSM) in Vancouver from 2012-2017.

METHODS

Respondent-driven sampling was used to recruit sexually active gbMSM (≥16 years) who completed biannual study visits with a computer-assisted self-interview and clinical CD4 and viral load (VL) testing. We linked participant data with the BC HIV Drug Treatment Program to obtain antiretroviral dispensing and VL data. We conducted a trend analysis of VL suppression using univariable generalized estimating equation (GEE) multi-level modelling and multivariable GEE to identify factors associated with episodes of VL ≥200 copies/mL.

RESULTS

Of 774 participants, 223 were living with HIV at baseline and 16 were diagnosed during follow-up (n = 239). We observed a significant trend towards reduced levels of unsuppressed VL (>200 copies/mL) from 22% (07/2012-12/2012) to 12% (07/2016-12/2016) (OR:0.87; 95%CI:0.83-0.91 for each 6-month period). Among those with at least one follow-up visit, (n = 178, median follow-up = 3.2 years, median age = 46.9 years), younger age (aOR:0.97; 95%CI:0.94-0.99, per year), ecstasy use (aOR:1.69; 95%CI:1.13-2.53), crystal methamphetamine use (aOR:1.71; 95%CI:1.18-2.48), seeking sex via websites (aOR:1.46; 95%CI:1.01-2.12), and lower HIV treatment optimism (aOR:0.94; 95%CI:0.90-0.97) were associated with episodes of elevated viremia.

CONCLUSIONS

During a period when TasP policy was actively promoted, we observed a significant trend towards reduced levels of unsuppressed VL. Continued efforts should promote HIV treatment optimism and engagement, especially among younger gbMSM and those who use ecstasy and crystal methamphetamine.

HIV prevalence and associated factors among female sex workers in Ethiopia, east Africa: A cross-sectional study using a respondent-driven sampling technique

BACKGROUND

HIV acquisition among Female Sex Workers (FSWs) is 30 times higher than the acquisition rate among females in the respective general population. A higher HIV burden in FSWs challenges the prevention and control of the virus in other population groups. However, there is inadequate evidence on the burden of HIV among FSWs in Ethiopia. This study was conducted to assess the extent of HIV and associated factors among FSWs in the country.

METHODS

This was a cross-sectional study that involved a total of 6,085 FSWs. The participants were selected using a respondent-driven sampling technique (RDS). FSWs who lived at the study sites for at least a month before the study time were considered eligible for recruitment. The study was conducted from January 01 to June 30, 2020 in 16 cities across Ethiopia. A mixed-effect logistic regression model was applied to determine factors associated with HIV positivity.

FINDINGS

The pooled HIV prevalence among FSWs in this study was 18·7% (95% CI: 17·8, 19·7) with considerable variation across cities. The highest HIV prevalence was observed in Bahir Dar city, 28·2% (95% CI: 23·9, 33.0) and the lowest was seen in Shashemene city, 14.0% (95% CI: 10·2, 18·9). The odds of HIV positivity in FSWs was associated with being older than 35 years of age (AOR = 8·1; 95% CI: 6·1, 10·3), reactive for Treponema Pallidum (AOR = 2·6; 95% CI: 1·0, 3·4), being widowed (OR = 2·2; 95% CI: 1·6, 2·9), not able to read and write (OR = 2·0; 95% CI: 1·5, 2·4), incidence of condom breakage (OR = 1·5; 95% CI: 1·2, 1·7) and having a history of STIs (OR = 1·3; 95% CI: 1·1, 1·6).

INTERPRETATION

One in five FSWs was HIV positive. HIV prevalence was higher in the older age groups and in those who were positive for Treponema Pallidum (Syphilis). The findings indicated the importance of strengthening HIV prevention and control in FSWs to achieve the national goal to eliminate HIV by 2030.

FUNDING

The study was supported by The Ethiopian Ministry of Health through the Federal HIV/AIDS Prevention and Control Office.

Summarizing methods for estimating population size for key populations: a global scoping review for human immunodeficiency virus research

BACKGROUND

Estimating the population sizes of key populations(people who inject drugs, men who have sex with men, transgender persons, and commercial sex workers) is critical for understanding the overall Human Immunodeficiency Virus burden. This scoping review aims to synthesize existing methods for population size estimation among key populations, and provide recommendations for future application of the existing methods.

METHODS

Relevant studies published from 1st January 2000 to 4th August 2020 and related to key population size estimation were retrieved and 120 of 688 studies were assessed. After reading the full texts, 81 studies were further excluded. Therefore, 39 studies were included in this scoping review. Estimation methods included five digital methods, one in-person method, and four hybrid methods.

FINDING

We summarized and organized the methods for population size estimateion into the following five categories: methods based on independent samples (including capture-recapture method and multiplier method), methods based on population counting (including Delphi method and mapping method), methods based on the official report (including workbook method), methods based on social network (including respondent-driven sampling method and network scale-up method) and methods based on data-driven technologies (Bayesian estimation method, Stochastic simulation method, and Laska, Meisner, and Siegel estimation method). Thirty-six (92%) articles were published after 2010 and 23 (59%) used multiple methods. Among the articles published after 2010, 11 in high-income countries and 28 in low-income countries. A total of 10 estimated the size of commercial sex workers, 14 focused on men who have sex with men, and 10 focused on people who inject drugs.

CONCLUSIONS

There was no gold standard for population size estimation. Among 120 studies that were related to population size estimation of key populations, the most commonly used population estimation method is the multiplier method (26/120 studies). Every method has its strengths and biases. In recent years, novel methods based on data-driven technologies such as Bayesian estimation have been developed and applied in many surveys.

Project BESPOKE (Integrated Bio-Behavioral Assessment of HIV and STI Among Young Tertiary Student Men Who Have Sex With Men in Nairobi, Kenya): A Respondent-Driven Sampling Survey Protocol

Introduction: Globally, men who have sex with men (MSM) are a key population for the human immunodeficiency virus (HIV) epidemic. Among MSM, young men who have sex with men (YMSM) are disproportionately affected by HIV and other sexually transmitted infections (STI). However, there is a dearth of research and interventions targeting HIV/STI prevention among YMSM. In Kenya, there is paucity of knowledge on the burden of HIV/STI and related factors among YMSM, including tertiary student men who have sex with men (TSMSM). The barriers TSMSM experience in accessing and utilizing health services in their learning institutions have seldom been explored. In the context of healthcare providers (HCP) working in tertiary institutions, little is known about their knowledge, attitudes, and practices toward providing services to TSMSM. Methods: The aims of the study are to: estimate prevalence and correlates of HIV/STI among TSMSM; estimate population size of TSMSM; explore experiences of TSMSM with access and utilization of health services; and assess HCP knowledge of, attitudes toward, and practices in provision of services to TSMSM. A mixed-methods approach will be used in three phases: Phase I-formative qualitative research will be conducted to understand TSMSM social networks, select "seeds", and explore strategies for implementing a respondent-driven sampling (RDS) survey. Interviews will be conducted with at least three staff who work in community based/non-governmental organizations (CBO/NGO) that serve MSM and at least 10 TSMSM. Phase II-an integrated bio-behavioral assessment (IBBA) will be conducted, where 200 TSMSM recruited by RDS will be offered HIV/STI testing, complete a behavioral survey, and provide information for population size estimation (PSE). Phase III-in-depth interviews will be held with 20 TSMSM selected from 200 TSMSM in phase II, to explore their experiences with access and utilization of healthcare services. Focus group discussions (FGD) will be conducted with HCP working in tertiary institutions to assess their knowledge of, attitudes toward, and practices in providing services to TSMSM. Data collection started in September 2020 and is expected to end by September 2021. Discussion: Findings from this study will be useful in informing HIV/STI prevention programming for TSMSM, by policy makers such the Kenyan ministries of health and education, tertiary education institutions, service providers, advocacy groups, and other interested stakeholders.

Undetectable or Unknown? A Longitudinal Event-Level Analysis of Disclosure of HIV Serostatus and Undetectability Among Gay, Bisexual, and Other Men Who have Sex with Men (gbMSM) in Metro Vancouver

We examined temporal trends and factors associated with reporting partner's serostatus and viral load among a sample of gay, bisexual and other men who have sex with men (gbMSM) in Vancouver, Canada. Participants were recruited using respondent-driven sampling and we collected prospective cohort data from 09/2014 to 02/2017 using a computer-assisted questionnaire and nurse-administered STI/HIV testing. Our study included 481 participants reporting on 3780 sexual events. Among HIV-negative/unknown gbMSM we found a trend towards decreased proportions of sexual events reporting an unknown HIV-status partner (42-19%; p =  < 0.001) and found increased proportions among gbMSM living with HIV (11-27%; p = 0.043). More participants living with HIV reported sex with undetectable partners, compared to HIV-negative/unknown participants (14.8% versus 5%). Our multivariable model found that compared with unknown status partners, undetectable partners were older, were from longer sexual relationships and were more likely to engage in condomless anal sex. Findings indicate that HIV-negative gbMSM seem more aware of the serostatus of their partners over time, but knowledge of partners' viral load over time was not significant. Further research should assess the degree to which new campaigns such as Undetectable = Untransmittable (U = U) are associated with discussions about HIV disclosure and viral load status.

Implementing Respondent-Driven Sampling to Recruit Women Who Exchange Sex in New York City: Factors Associated with Recruitment and Lessons Learned

Respondent-driven sampling (RDS) relies on productive peer recruitment to capture hidden populations. Domestic studies have identified characteristics of productive recruitment among RDS samples of men who have sex with men and persons who use drugs, but not of women who exchange sex, a group vulnerable to HIV infection. We examined sociodemographic-, behavioral-, exchange-sex-, and protocol-related factors associated with recruitment among seeds (n = 25) and peers (n = 297) in the 2016 New York City National HIV Behavioral Surveillance Study cycle focused on women who exchange sex. Recruiter productivity was significantly associated with not having been recently incarcerated, lower rate of HIV testing, and larger exchange sex networks among seeds, and with HIV-prevention services usage among peers. We describe challenges and lessons learned from implementing RDS in this population. Our study identifies seed characteristics and protocol improvements researchers can utilize when implementing future RDS studies among women who exchange sex.

A Longitudinal Examination of Factors Associated with Network Bridging Among YMSM: Implications for HIV Prevention

Social-environmental factors may be associated with social network stability, which has implications for HIV acquisition. However, the link between social-environmental factors, network composition and HIV risk has not been examined previously among a city-population based sample of young Black men who have sex with Men (YBMSM). Respondent driven sampling was used to recruit a cohort of 618 YMBSM. Respondents were evaluated at baseline, 9 and 18 months beginning June 2013. A logistic regression model was used to assess the relationship between bridging (i.e. having non-redundant contacts in one's network, indicating network instability) and social-environmental factors and HIV risk factors between respondents, and a conditional logit model was used to assess these relationships within respondents over time. Bridging was associated with adverse social-environmental factors and higher HIV risk, indicating that bridging may be on the explanatory pathway. Future studies should assess the extent to which network stability factors mitigate HIV risk.

HIV Testing Among a Representative Community Sample of Gay, Bisexual, and Other Men Who Have Sex with Men in Vancouver, Canada

Earlier HIV diagnosis allows for improved treatment outcomes and secondary prevention. It is recommended that all individuals know their HIV status and that those at higher risk test more frequently. Using a representative community sample of gay, bisexual, and other men who have sex with men (GBMSM), we aimed to: (1) determine the proportion of GBMSM who have tested in the past 2 years, (2) determine reasons for testing and never having tested, and (3) explore correlates of testing. Of 535 eligible participants, 80.0% reported having had an HIV test in the past 2 years, most commonly as part of a regular testing schedule. The most common reason for not testing was low perceived HIV risk. Bisexual and older GBMSM, as well as those who lived outside of Vancouver, were less likely to have tested in the past 2 years. Rapid point-of-care testing may help improve testing rates and was shown to effectively engage some hard-to-reach GBMSM (e.g., those who had not tested for other STIs) in this sample.

Seroadaptive Strategies of Vancouver Gay and Bisexual Men in a Treatment as Prevention Environment

British Columbia's treatment as prevention policy has provided free access to highly active antiretroviral therapy (HAART) to all HIV-positive provincial residents since 1996. One outcome is an increase in HIV-positive gay and bisexual men (GBM) with suppressed viral loads. Previous cross-sectional analyses indicated that some Vancouver GBM now recognize condomless anal sex with men on HAART who report a suppressed viral load as a seroadaptive strategy. To test the hypothesis that this new strategy, termed viral load sorting (VLS), is recognized and used among by GBM in the Momentum Health Study, we analyzed longitudinal data for HIV-negative/unknown (n = 556) and HIV-positive (n = 218) serostatus participants. Analyses indicated that both groups reported VLS, and that serostatus and Treatment Optimism Scale scores were significant determinants in frequency and use. Results exemplify the medicalization of sex and Rogers' Diffusion Of Preventative Innovations Model, and they have important implications for HIV research and GBM sexual decision-making.