Respondent-driven sampling to assess characteristics and estimate the number of injection drug users in Bangkok, Thailand

Population Size Estimation Using Multiple Respondent-Driven Sampling Surveys

Respondent-driven sampling (RDS) is commonly used to study hard-to-reach populations since traditional methods are unable to efficiently survey members due to the typically highly stigmatized nature of the population. The number of people in these populations is of primary global health and demographic interest and is usually hard to estimate. However, due to the nature of RDS, current methods of population size estimation are insufficient. We introduce a new method of estimating population size that uses concepts from capture-recapture methods while modeling RDS as a successive sampling process. We assess its statistical validity using information from the CDC's National HIV Behavioral Surveillance system in 2009 and 2012.

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

Background

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

Methods

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

Results

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

Conclusion

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

HIV Incidence and Risk Behaviours of People Who Inject Drugs in Bangkok, 1995-2012

BACKGROUND

Three consecutive prospective studies were conducted among people who inject drugs (PWID) from May 1995 through June 2012 in Bangkok, Thailand. We examined data from these studies to evaluate HIV incidence and explore trends in risk behaviours.

METHODS

We used data from a 1995-1998 cohort study, a 1999-2004 HIV vaccine trial, and a 2005-2012 HIV pre-exposure prophylaxis (PrEP) study to examine per-quarter trends in HIV incidence, using a restricted cubic spline function for time in a Poisson regression. We also examined temporal trends in HIV-associated risk behaviours.

FINDINGS

HIV incidence declined from 5.7 per 100 person-years during the cohort study, to 2.7 per 100 person-years in the vaccine trial, to 0.7 per 100 person-years among PrEP study placebo recipients. Incidence peaked at 12.1 per 100 person-years in 1996 and declined to < 1 per 100 person-years during 2005-2012. Reports of injecting drugs and sharing needles also declined from the cohort study to the PrEP study (p < 0.0001). Heroin was the most common drug injected during the cohort study and the vaccine trial, but stimulants (e.g., methamphetamine) and sedatives (e.g., midazolam) were injected more often during the PrEP study.

INTERPRETATION

HIV incidence among PWID declined during 2005-2012. Several factors likely contributed to the decline, including decreases in the frequency of injecting and sharing, improved access to HIV testing and antiretroviral therapy, and the use of PrEP. Expanding access to effective HIV prevention tools can hasten control of the HIV epidemic among PWID.

FUNDING

The Bangkok Metropolitan Administration and U.S. Centers for Disease Control and Prevention, Division of HIV/AIDS Prevention.

HIV, Hepatitis B and C among people who inject drugs: high prevalence of HIV and Hepatitis C RNA positive infections observed in Delhi, India

Background

India has large PWID (persons who inject drugs) population estimated at 177,000. PWIDs are at high risk for HIV, Hepatitis B (HBV) and Hepatitis C (HCV) infections. We report the prevalence of HIV, HBV and HCV infections and correlates of HIV-HCV co-infection among male PWIDs in Delhi.

Methods

3748 male PWIDs were recruited for a longitudinal HIV incidence study. Participants were tested for HBV and HCV infections at their first follow-up visit (FV1) using serum HBV-surface antigen, and HCV-antibody tests followed by HCV RNA PCR, respectively. All PWIDs who were HIV-negative at enrollment, were re-tested for HIV at FV1. Multinomial logistic regression was employed to identify predictors of HIV, HCV and HIV-HCV co-infection.

Results

Overall prevalence of HIV, HBV and HCV among 2,292 participants tested at FV1 was 25.9 %, 9.7 % and 53.7 %, respectively. 6.4 % of the participants had HIV mono-infection, 34.1 % had HCV mono-infection, and 19.6 % had HIV-HCV co-infection. 26 % of HIV-positive participants without HCV were HBsAg positive.

In the regression model, having practiced at least one risky injection in the past month (relative risk ratio (RRR): 1.38; 95 % CI: 1.01-1.89) and not knowing his own HIV status (RRR: 1.65, 95 % CI: 1.25-2.17) were independent predictors for HIV-HCV co-infection. Longer duration of drug injections was associated with a higher likelihood of HCV mono-infection (2–5 years RRR: 2.13; 6–10 years RRR: 2.74; ≥11 years RRR: 3.14) and HIV-HCV co-infection (2–5 years RRR: 5.14; 6–10 years RRR: 8.53; >11 years RRR: 8.03). Higher frequency of injection days/month was associated with a higher likelihood of HCV mono-infection (≤10 days/month RRR: 1.61; 11–20 days/month RRR: 3.15; 21–30 days/month RRR: 3.47) and HIV-HCV co-infections (≤10 days/month RRR: 2.26; 11–20 days/month RRR: 3.46; 21–30 days/month RRR: 4.83).

Conclusions

We report a high prevalence of HIV, HCV and HIV-HCV co-infection among male PWIDs in Delhi. A tenth of the participants were HBsAg positive. Targeted Intervention programs should make HBV/HCV testing, prevention and care more accessible for PWIDs.

High Mortality Among Non-HIV-Infected People Who Inject Drugs in Bangkok, Thailand, 2005-2012

OBJECTIVES

We examined the causes of hospitalization and death of people who inject drugs participating in the Bangkok Tenofovir Study, an HIV preexposure prophylaxis trial.

METHODS

The Bangkok Tenofovir Study was a randomized, double-blind, placebo-controlled trial conducted during 2005 to 2012 among 2413 people who inject drugs. We reviewed medical records to define the causes of hospitalization and death, examined participant characteristics and risk behaviors to determine predictors of death, and compared the participant mortality rate with the rate of the general population of Bangkok, Thailand.

RESULTS

Participants were followed an average of 4 years; 107 died: 22 (20.6%) from overdose, 13 (12.2%) from traffic accidents, and 12 (11.2%) from sepsis. In multivariable analysis, older age (40-59 years; P = .001), injecting drugs (P = .03), and injecting midazolam (P < .001) were associated with death. The standardized mortality ratio was 2.9.

CONCLUSIONS

People who injected drugs were nearly 3 times as likely to die as were those in the general population of Bangkok and injecting midazolam was independently associated with death. Drug overdose and traffic accidents were the most common causes of death, and their prevention should be public health priorities.

Diverse HIV epidemics among people who inject drugs in Thailand: evidence from respondent-driven sampling surveys in Bangkok and Chiang Mai

BACKGROUND

Thailand's long-standing HIV sero-sentinel surveillance system for people who inject drugs (PWID) is confined to those in methadone-based drug treatment clinics and representative data are scarce, especially outside of Bangkok.

METHODS

We conducted probability-based respondent-driven sampling (RDS) surveys in Bangkok (n=738) and Chiang Mai (n=309) to increase understanding of local HIV epidemics and to better inform the planning of evidence-based interventions.

RESULTS

PWID had different epidemiological profiles in these two cities. Overall HIV prevalence was higher in Bangkok (23.6% vs. 10.9%, p<0.001) but PWID in Bangkok are older and appear to have long-standing HIV infections. In Chiang Mai, HIV infections appear to be more recently acquired and PWID were younger and had higher levels of recent injecting and sexual risk behaviors with lower levels of intervention exposure. Methamphetamine was the predominant drug injected in both sites and polydrug use was common although levels and patterns of the specific drugs injected varied significantly between the sites. In multivariate analysis, recent midazolam injection was significantly associated with HIV infection in Chiang Mai (adjusted odds ratio=8.1; 95% confidence interval: 1.2-54.5) whereas in Bangkok HIV status was not associated with recent risk behaviors as infections had likely been acquired in the past.

CONCLUSION

PWID epidemics in Thailand are heterogeneous and driven by local factors. There is a need to customize intervention strategies for PWID in different settings and to integrate population-based survey methods such as RDS into routine surveillance to monitor the national response.

Using a 2-stage strategy with respondent-driven sampling to recruit a hard-to-reach population for a placebo microbicide gel clinical trial in Nellore, Andhra Pradesh (India)

Traditional recruitment methods for microbicide efficacy trials are labor intensive and may fail to reach high-risk hard-to-reach populations. We report duration of recruitment and lessons learned from a two-stage process to recruit female sex workers (FSWs) into a placebo microbicide trial, and examined characteristics associated with successful recruitment of peers who screened for and enrolled in the trial. FSWs were first recruited via respondent-driven sampling (RDS) to complete a survey and subsequently invited to screen for enrollment into a placebo microbicide trial taking place at a local clinic. It took 6 months to enroll 267 participants into the trial. Successful recruiters of peers who enrolled were more likely to have enrolled themselves (AOR 2.0, CI 1.3-2.9) and less likely to visit Nellore city (AOR 0.5, CI 0.3-0.9). Recruitment of FSWs via a two-stage recruitment strategy with RDS can be a good option for future clinical trials.

Readjustment of Urban Veterans: A Mental Health and Substance Use Profile of Iraq and Afghanistan Veterans in Higher Education

OBJECTIVE

To identify the prevalence of substance use and mental health problems among veterans and student service members/veterans (SSM/V) returning from Iraq and Afghanistan to New York City's low-income neighborhoods.

PARTICIPANTS

A sample of 122 veterans attending college and 116 veterans not enrolled recruited using respondent-driven sampling.

METHODS

Logistic regression analysis of variation in characteristics of those veterans attending college; linear regression examining effects of college attendance on life satisfaction.

RESULTS

Having a traumatic brain injury or disability was positively associated with college attendance. Being married, employed, or in college was predictive of overall life satisfaction. SSM/V were significantly less likely to screen positive for depression or drug use disorder. African American veterans were significantly less likely to attend college than white or Hispanic veterans.

CONCLUSION

Substance use and some mental health disorders do not preclude inner-city veterans from entering higher education. This study contributes to the sparse literature on African American veterans and SSM/V.

Lessons learned from a review of interventions for adolescent and young key populations in Asia Pacific and opportunities for programming

BACKGROUND

Over a third of new HIV infections globally are among 15-24 year-olds and over 20% among adolescents aged 10-19 years in Asia Pacific. The review was initiated to identify interventions in the region with demonstrated or potential impact for adolescent and young key populations (YKP) looking at the role of individual and structural factors in accessibility and delivery. The review is a component of a more comprehensive review undertaken by UNICEF and partners in the region.

METHODS

This was a desk review of over 1000 articles, and 37 were selected. Journal articles in PubMed, Cochrane Library, Cochrane DARE, EMBASE, PsycINFO, CINAHL, and Web of Science databases were searched for HIV intervention-related information for adolescent and YKP.

RESULTS AND DISCUSSION

Findings showed that except for low levels of risk perception, most individual decisions regarding safe behavior and testing uptake were mediated by structural factors. Critical enablers such as design and delivery of services, peer education, and condom policies were associated with the uptake of high-impact interventions. Synergistic development interventions such as sexuality education, rights-based enforcement of antitrafficking laws, and addressing violence and abuse could increase safer behaviors.

CONCLUSIONS

Although structural factors play a key role in access and uptake of HIV prevention services for adolescent and YKP, further qualitative research is needed to understand and mitigate the drivers of vulnerability and constructed perceptions of risk.

Risk behaviors and risk factors for HIV infection among participants in the Bangkok tenofovir study, an HIV pre-exposure prophylaxis trial among people who inject drugs

INTRODUCTION

HIV spread rapidly among people who inject drugs in Bangkok in the late 1980s. In recent years, changes in drug use and HIV-associated risk behaviors have been reported. We examined data from the Bangkok Tenofovir Study, an HIV pre-exposure prophylaxis trial conducted among people who inject drugs, to assess participant risk behavior and drug use, and to identify risk factors for HIV infection.

METHODS

The Bangkok Tenofovir Study was a randomized, double-blind, placebo-controlled trial. HIV status was assessed monthly and risk behavior every 3 months. We used generalized estimating equations logistic regression to model trends of injecting, needle sharing, drugs injected, incarceration, and sexual activity reported at follow-up visits; and proportional hazards models to evaluate demographic characteristics, sexual activities, incarceration, drug injection practices, and drugs injected during follow-up as predictors of HIV infection.

RESULTS

The proportion of participants injecting drugs, sharing needles, and reporting sex with more than one partner declined during follow-up (p<0.001). Among participants who reported injecting at enrollment, 801 (53.2%) injected methamphetamine, 559 (37.1%) midazolam, and 527 (35.0%) heroin. In multivariable analysis, young age (i.e., 20-29 years) (p = 0.02), sharing needles (p<0.001), and incarceration in prison (p = 0.002) were associated with incident HIV infection. Participants reporting sex with an opposite sex partner, live-in partner, casual partner, or men reporting sex with male partners were not at a significantly higher risk of HIV infection compared to those who did not report these behaviors.

CONCLUSION

Reports of HIV-associated risk behavior declined significantly during the trial. Young age, needle sharing, and incarceration were independently associated with HIV infection. Sexual activity was not associated with HIV infection, suggesting that the reduction in HIV incidence among participants taking daily oral tenofovir compared to those taking placebo was due to a decrease in parenteral HIV transmission.

Substance use over the military-veteran life course: an analysis of a sample of OEF/OIF veterans returning to low-income predominately minority communities

This paper presents an overview of substance use patterns of recent veterans returning to low-income predominately minority communities over four periods of the military-veteran career. Respondent driven sampling (RDS) was used so that unbiased estimates could be obtained for the characteristics of the target population. The majority of participants had used marijuana but no other illegal drugs. In the military, marijuana use was substantially lower and alcohol was the drug of choice; the majority were binge drinkers and nearly half were heavy drinkers. While deployed, alcohol and marijuana use were both lower, though some participants (6%) initiated the misuse of prescription painkillers. After separating from the military and returning to civilian life, heavy drinking was much lower, marijuana use increased, and some veterans misused prescription painkillers (7%). Further research based on these data will examine these distinct periods of substance use, contexts of use, related substance and mental health problems, treatment use and avoidance, and civilian reintegration.

Biomedical HIV prevention research and epidemic control in Thailand: two sides of the same coin

For a country with a moderate adult HIV prevalence of just over 1% in 2012, Thailand is widely perceived as having made some extraordinary contributions to the global management of the HIV/AIDS pandemic. It has been promoted as a model of effective HIV control and applauded for its leadership in providing access to antiretroviral treatment. Thailand has also received international recognition for its contribution to biomedical HIV prevention research, which is generally perceived as exceptional. In this paper, Thailand's global role model function as an example of effective HIV/AIDS control and high-quality biomedical HIV prevention research is re-evaluated against the background of currently available data and more recent insights. The results indicate that Thailand's initial response in raising the level of the political significance of HIV/AIDS was indeed extraordinary, which probably prevented a much larger epidemic from occurring. However, this response transpired in unusual extraconstitutional circumstances and its effectiveness declined once the country returned to political normalcy. Available data confirm the country's more than exceptional contribution to biomedical HIV prevention research. Thailand has made a huge contribution to the global management and control of the HIV/AIDS pandemic.

Incorporating the service multiplier method in respondent-driven sampling surveys to estimate the size of hidden and hard-to-reach populations: case studies from around the world

BACKGROUND

Estimating the sizes of populations at highest risk for HIV is essential for developing and monitoring effective HIV prevention and treatment programs. We provide several country examples of how service multiplier methods have been used in respondent-driven sampling surveys and provide guidance on how to maximize this method's use.

METHODS

Population size estimates were conducted in 4 countries (Mauritius- intravenous drug users [IDU] and female sex workers [FSW]; Papua New Guinea-FSW and men who have sex with men [MSM]; Thailand-IDU; United States-IDU) using adjusted proportions of population members reporting attending a service, project or study listed in a respondent-driven sampling survey, and the estimated total number of population members who visited one of the listed services, projects, or studies collected from the providers.

RESULTS

The median population size estimates were 8866 for IDU and 667 for FSW in Mauritius. Median point estimates for FSW were 4190 in Port Moresby and 8712 in Goroka, Papua New Guinea, and 2,126 for MSM in Port Moresby and 4200 for IDU in Bangkok, Thailand. Median estimates for IDU were 1050 in Chiang Mai, Thailand, and 15,789 in 2005 and 15,554 in 2009 in San Francisco.

CONCLUSION

Our estimates for almost all groups in each country fall within the range of other regional and national estimates, indicating that the service multiplier method, assuming all assumptions are met, can produce informative estimates. We suggest using multiple multipliers whenever possible, garnering program data from the widest possible range of services, projects, and studies. A median of several estimates is likely more robust to potential biases than a single estimate.

Drug-related harm among people who inject drugs in Thailand: summary findings from the Mitsampan Community Research Project

Background

For decades, Thailand has experienced high rates of illicit drug use and related harms. In response, the Thai government has relied on drug law enforcement to address this problem. Despite these efforts, high rates of drug use persist, and Thailand has been contending with an enduring epidemic of human immunodeficiency virus (HIV) among people who inject drugs (IDU).

Methods

In response to concerns regarding drug-related harm in Thailand and a lack of research focused on the experiences and needs of Thai IDU, the Mitsampan Community Research Project was launched in 2008. The project involved administering surveys capturing a range of behavioral and other data to community-recruited IDU in Bangkok in 2008 and 2009.

Results

In total, 468 IDU in Bangkok were enrolled in the project. Results revealed high rates of midazolam injection, non-fatal overdose and incarceration. Syringe sharing remained widespread among this population, driven primarily by problems with access to syringes and methamphetamine injection. As well, reports of police abuse were common and found to be associated with high-risk behavior. Problems with access to evidence-based drug treatment and HIV prevention programs were also documented. Although compulsory drug detention centers are widely used in Thailand, data suggested that these centers have little impact on drug use behaviors among IDU in Bangkok.

Conclusions

The findings from this project highlight many ongoing health and social problems related to illicit drug use and drug policies in Bangkok. They also suggest that the emphasis on criminal justice approaches has resulted in human rights violations at the hands of police, and harms associated with compulsory drug detention and incarceration. Collectively, the findings indicate the urgent need for the implementation of evidence-based policies and programs in this setting.

The effect of exposures to policing on syringe sharing among people who inject drugs in Bangkok, Thailand

While intensive drug law enforcement is recognized as a social-structural driver of HIV epidemics among people who inject drugs (IDU), few studies have investigated the effects of direct encounters with police, particularly in Asian settings. Using multivariate log-binomial regression, we examined the relationship between syringe sharing and exposures to two types of policing practices among IDU in Bangkok, Thailand: having been beaten by police and having been tested for illicit drugs by police. Between July and October 2011, 435 IDU participated in the study, with 75 (17.2 %) participants reporting syringe sharing in the past 6 months. In multivariate analyses, exposures to the two types of policing practices had an independent effect on syringe sharing, with experiencing both practices showing the greatest effect. These findings highlight the importance of addressing the policy and social environment surrounding IDU as a means of HIV prevention.

High uptake of HIV testing in a cohort of male injection drug users in Delhi, India: prevalence and correlates of HIV infection

We report baseline findings from a longitudinal cohort study to examine HIV incidence, high-risk injection and sexual behaviors of 3,792 male injection drug users (IDUs) in Delhi. The majority (95.4 %) accepted HIV testing; HIV prevalence was 21.9 %. In multivariate analysis, belonging to states adjacent to Delhi (AOR: 1.23; 95 % CI: 1.07-1.52), earning INR 500-1,500 (AOR: 2.38; 95 % CI: 1.43-3.96); duration of drug use 2-5 years (AOR: 2.02; 95 % CI: 1.09-3.73), 6-10 years (AOR: 2.81; 95 % CI: 1.55-5.11), ≥11 years (AOR: 3.35; 95 % CI: 1.84-6.11); prior HIV testing (AOR: 1.60; 95 % CI: 1.35-1.91), self-reported risky-injection behavior (AOR: 1.60; 95 % CI: 1.33-1.92), and utilization of harm-reduction services (AOR: 1.32; 95 % CI: 1.11-1.58) were positively associated with HIV infection. Alcohol use ≤2 times/week (AOR: 0.67; 95 % CI: 0.55-0.82) or ≥3 times/week (AOR: 0.74; 95 % CI: 0.54-1.01), unit increase in age (AOR: 0.99; 95 % CI: 0.98-1.00), ≥7 years of schooling (AOR: 0.82; 95 % CI: 0.66-1.02) and unsafe sex with any female partner (AOR: 0.69; 95 % CI: 0.55-0.86) were negatively associated with HIV infection. HIV prevalence remains high among male IDUs in Delhi. HIV prevention programs should include comprehensive package of services for IDUs.

Prescription opioid initiation, correlates, and consequences among a sample of OEF/OIF military personnel

Prescription opioid (PO) misuse represents a major health risk for many service members and veterans. This paper examines the pathways to misuse among a sample of U.S. veterans who recently returned from Iraq and Afghanistan to low-income, predominately minority sections of New York City. Recreational PO misuse was not common on deployment. Most PO misusers initiated use subsequent to PO use for pain management, an iatrogenic pathway. However, most PO users did not misuse them. Veterans that misused POs were more likely to have other reintegration problems including drug and alcohol use disorders, traumatic brain injury (TBI), unemployment, and homelessness.

Substance use and other mental health disorders among veterans returning to the inner city: prevalence, correlates, and rates of unmet treatment need

Estimates of substance use and other mental health disorders of veterans (N = 269) who returned to predominantly low-income minority New York City neighborhoods between 2009 and 2012 are presented. Although prevalences of posttraumatic stress disorder, traumatic brain injury, and depression clustered around 20%, the estimated prevalence rates of alcohol use disorder, drug use disorder, and substance use disorder were 28%, 18%, and 32%, respectively. Only about 40% of veterans with any diagnosed disorder received some form of treatment. For alcohol use disorder, the estimate of unmet treatment need was 84%, which is particularly worrisome given that excessive alcohol use was the greatest substance use problem.

Beyond indicators: advances in global HIV monitoring and evaluation during the PEPFAR era

Monitoring and evaluation (M&E) is fundamental to global HIV program implementation and has been a cornerstone of the President's Emergency Plan for AIDS Relief (PEPFAR). Rapid results were crucial to demonstrating feasibility and scalability of HIV care and treatment services early in PEPFAR. When national HIV M&E systems were nascent, the rapid influx of funds and the emergency expansion of HIV services contributed to the development of uncoordinated "parallel" information systems to serve donor demands for information. Close collaboration of PEPFAR with multilateral and national partners improved harmonization of indicators, standards, methods, tools, and reports. Concurrent PEPFAR investments in surveillance, surveys, program monitoring, health information systems, and human capacity development began to show signs of progress toward sustainable country-owned systems. Awareness of the need for and usefulness of data increased, far beyond discussions of indicators and reporting. Emphasis has turned toward ensuring the quality of data and using available data to improve the quality of care. Assessing progress toward an AIDS-free generation requires that the global community can measure the reduction of new HIV infections in children and adults and monitor the coverage, quality, and outcomes of highly efficacious interventions in combination. Building national M&E systems requires sustained efforts over long periods of time with effective leadership and coordination. PEPFAR, in close collaboration with its global and national partners, is well positioned to transform the successes and challenges associated with early rapid scale-up into future opportunities for sustainable, cost-effective, country-owned programs and systems.

Enrollment characteristics and risk behaviors of injection drug users participating in the Bangkok Tenofovir Study, Thailand

Background

The Bangkok Tenofovir Study was launched in 2005 to determine if pre-exposure prophylaxis with tenofovir will reduce the risk of HIV infection among injecting drug users (IDUs). We describe recruitment, screening, enrollment, and baseline characteristics of study participants and contrast risk behavior of Tenofovir Study participants with participants in the 1999–2003 AIDSVAX B/E Vaccine Trial.

Methods

The Bangkok Tenofovir Study is an ongoing, phase-3, randomized, double-blind, placebo-controlled, HIV pre-exposure prophylaxis trial of daily oral tenofovir. The Tenofovir Study and the Vaccine Trial were conducted among IDUs at 17 drug-treatment clinics in Bangkok. Tenofovir Study sample size was based on HIV incidence in the Vaccine Trial. Standardized questionnaires were used to collect demographic, risk behavior, and incarceration data. The Tenofovir Study is registered with ClinicalTrials.gov, number-NCT00119106.

Results

From June 2005 through July 2010, 4094 IDUs were screened and 2413 enrolled in the Bangkok Tenofovir Study. The median age of enrolled participants was 31 years (range, 20–59), 80% were male, and 63% reported they injected drugs during the 3 months before enrollment. Among those who injected, 53% injected methamphetamine, 37% midazolam, and 35% heroin. Tenofovir Study participants were less likely to inject drugs, inject daily, or share needles (all, p<0.001) than Vaccine Trial participants.

Discussion

The Bangkok Tenofovir Study has been successfully launched and is fully enrolled. Study participants are significantly less likely to report injecting drugs and sharing needles than participants in the 1999–2003 AIDSVAX B/E Vaccine Trial suggesting HIV incidence will be lower than expected. In response, the Bangkok Tenofovir Study enrollment was increased from 1600 to 2400 and the study design was changed from a defined 1-year follow-up period to an endpoint-driven design. Trial results demonstrating whether or not daily oral tenofovir reduces the risk of HIV infection among IDUs are expected in 2012.

Bridging populations-sexual risk behaviors and HIV prevalence in clients and partners of female sex workers, Bangkok, Thailand 2007

The aim of this study is to estimate HIV prevalence and assess sexual behaviors in a high-risk and difficult-to-reach population of clients of female sex workers (FSWs). A modified variation of respondent-driven sampling was conducted among FSWs in Bangkok, where FSWs recruited 3 FSW peers, 1 client, and 1 nonpaying partner. After informed consent was obtained, participants completed a questionnaire, were HIV-tested, and were asked to return for results. Analyses were weighted to control for the design of the survey. Among 540 FSWs, 188 (35%) recruited 1 client, and 88 (16%) recruited 1 nonpaying partner. Clients' median age was 38 years. HIV prevalence was 20% and was associated with younger age at first sexual experience [relative risk (RR) = 3.10, 95% confidence interval (CI) 1.16-8.24] and condom use during last sexual encounter with regular partner (RR = 3.97, 95% CI 1.09-14.61). Median age of nonpaying partners was 34 years, and HIV prevalence was 15.1%. There were 56 discordant FSW-client pairs and 14 discordant FSW-nonpaying partner pairs. Condom use was relatively high among discordant FSW-client pairs (90.1%) compared to discordant FSW-nonpaying partner pairs (18.7%). Results suggest that sexual partners of FSWs have a high HIV prevalence and can be a bridge for HIV transmission to other populations. Findings also highlight the importance of initiating surveillance and targeted programs for FSW partners, and demonstrate a recruitment method for hard-to-reach populations.

Methamphetamine injection and syringe sharing among a community-recruited sample of injection drug users in Bangkok, Thailand

BACKGROUND

The recent growth in methamphetamine use internationally has raised concerns about the relationship between methamphetamine use and HIV infection. However, the risks associated with methamphetamine injection have not been fully described, particularly outside of Western countries. Therefore, we sought to examine the relationship between methamphetamine injection and syringe sharing among injection drug users (IDU) in Bangkok, Thailand.

METHODS

Using bivariate statistics and multivariate logistic regression, we examined the prevalence of methamphetamine injection and the relationship between more than weekly methamphetamine injection and syringe sharing among a community-recruited sample of IDU participating in the Mitsampan Community Research Project in Bangkok.

RESULTS

During June and July 2009, 311 IDU participated in this study, including 91 (29.3%) women. In total, 114 (36.7%) participants reported having injected methamphetamine ("yaba") twice or more per week in the past six months. In multivariate analyses, after adjustment for potential social, demographic and behavioral confounders, syringe sharing remained independently associated with injecting methamphetamine more than once per week (adjusted odds ratio=2.86, 95% confidence interval: 1.59-5.15).

CONCLUSIONS

Over one-third of a community-recruited sample of Thai IDU reported more than weekly injection of methamphetamine, and methamphetamine injection was independently associated with syringe sharing. Essential HIV prevention services targeting IDU, such as syringe exchange and evidence-based addiction treatment, should be included in interventional efforts to address methamphetamine use in Thailand.

Measuring the incidence, prevalence and genetic relatedness of hepatitis C infections among a community recruited sample of injecting drug users, using dried blood spots

Monitoring hepatitis C virus (HCV) infection among injecting drug users (IDUs) in the community is complicated by difficulties in obtaining biological specimens and biases in recruitment and follow-up. This study examined the utility of dried blood spot (DBS) specimens from IDUs recruited using respondent-driven sampling (RDS). Active IDUs underwent a computer-assisted interview and provided a DBS sample, tested for HCV antibody (anti-HCV) and HCV-RNA. HCV incidence was estimated from the proportion of anti-HCV-negative subjects found HCV-RNA-positive and estimates of the duration of this state. Results were adjusted according to RDS derived sample weights. HCV-RNA testing was performed on 288 DBS samples; 173 were anti-HCV-positive (54% weighted), of which 70 (42%, 95%CI 34-50% weighted) were RNA-negative indicating cleared infection. Among the 115 anti-HCV-negatives, 14 were RNA-positive suggesting an incidence of 38-47 per 100pyrs. Incident infections were younger than anti-HCV-negative and prevalent infections: 25 vs. 29 and 34, respectively. Incidence was highest among individuals with poor needle exchange coverage. One hundred and fourteen were genotyped (60 1a, 46 3a): a cluster of 14 had homology of >98.5% including 10 incident infections. Public health surveillance of HCV among IDUs could be enhanced through the collection of DBS samples with appropriate recruitment approaches. DBS allow differentiation between individuals with cleared infections, ongoing infection and those recently infected. They also enable virus characterization at genotype and nucleotide level. This would allow surveillance to inform development of harm reduction interventions, and the international evidence base for these.

Cannabis Dependence and Peer Selection in Social Networks of Frequent Users

In a Dutch longitudinal study on the dynamics of cannabis dependence, at baseline 600 frequent cannabis users (? 3 days cannabis use per week in past 12 months) aged 18–30 years were interviewed. Nearly half of all participants (42%) met DSM-IV criteria for cannabis dependence in the 12 months prior to the interview. Participants were recruited by respondent-driven sampling; referrals were understood as proxy for social networks to explore peer associations and social exclusion. Analyses revealed that networks of frequent cannabis users were mostly heterogeneous. Cannabis dependence did not emerge as a main selector. However, within segments of networks some clustering of cannabis dependence (indicating differential inclusion), sex and ethnicity was found. Methodological questions are discussed regarding the applicability of respondent-driven sampling in noninjecting, nonmarginalized drug users. The study's limitations are noted.

Implementation of respondent-driven sampling among female sex workers in Brazil, 2009

Female sex workers are known in Brazil and elsewhere in the world as one of the most-at-risk populations for risk of HIV infection, due to their social vulnerability and factors related to their work. However, the use of conventional sampling strategies in studies on most-at-risk subgroups for HIV is generally problematic, since such subgroups are small in size and are associated with stigmatized behaviors and/or illegal activities. In 1997, a probabilistic sampling technique was proposed for hard-to-reach populations, called Respondent-Driven Sampling (RDS). The method is considered a variant of chain sampling and allows the statistical estimation of target variables. This article describes some assumptions of RDS and all the implementation stages in a study of 2,523 female sex workers in 10 Brazilian cities. RDS proved appropriate for recruiting sex workers, allowing the selection of a probabilistic sample and the collection of previously missing information on this group in Brazil.

Prevalence of HIV/HCV/HBV infections and drug-related risk behaviours amongst IDUs recruited through peer-driven sampling in Iran

BACKGROUND

The control of blood-borne infections including HIV and hepatitis C (HCV) amongst injecting drug users (IDUs) is a challenge for health authorities in Iran. Hence, more reliable estimates of the levels of blood-borne infections and their associated factors are critically needed.

METHODS

Active IDUs were recruited using peer-driven sampling in a bio-behavioural survey in 2008. Over 8 weeks, data were collected from adults living in a city in Isfahan Province who had injected drugs in the past month. Participants provided a whole blood sample and answered questions on sexual and drug-related risk characteristics. Participants were provided post-test counselling and a non-monetary incentive for their participation. Excluding two inactive cases, the initial recruits resulted in 2-8 waves of recruitment.

RESULTS

Overall, 118 IDUs including three females participated. The estimated population proportions of HIV, hepatitis B, and HCV infections were 0.7% (95% CI, 0.6-2.3), 0.7% (95% CI, 0.1-2.1), and 59.4% (95% CI, 47.4-68.7), respectively. Responses indicated that 31% (95% CI, 20-44.5) of the IDUs ever shared a needle/syringe for drug injection, and 77% (95% CI, 65-84) had ever injected an addictive solution marketed widely as Temgesic. Multivariate analyses revealed that the high prevalence of HCV infection amongst IDUs is associated with the lifetime duration of drug injection (AOR, 1.17; 95% CI, 1.01-1.34) and with having injected Temgesic (AOR, 4.73; 95% CI, 1.52-14.69).

CONCLUSION

Our experience in Iran indicates that IDUs can be recruited effectively in a bio-behavioural survey through peer-driven sampling and using only a single primary incentive. The high prevalence of HCV associated with injecting Temgesic is important evidence for harm-reduction policies in Iran.

Evaluating respondent-driven sampling in a major metropolitan area: Comparing injection drug users in the 2005 Seattle area national HIV behavioral surveillance system survey with participants in the RAVEN and Kiwi studies

PURPOSE

To empirically evaluate respondent-driven sampling (RDS) recruitment methods, which have been proposed as an advantageous means of surveying hidden populations.

METHODS

The National HIV Behavioral Surveillance system used RDS to recruit 370 injection drug users (IDU) in the Seattle area in 2005 (NHBS-IDU1). We compared the NHBS-IDU1 estimates of participants' area of residence, age, race, sex, and drug most frequently injected to corresponding data from two previous surveys, the RAVEN and Kiwi Studies, and to persons newly diagnosed with HIV/AIDS and reported from 2001 through 2005.

RESULTS

The NHBS-IDU1 population was estimated to be more likely to reside in downtown Seattle (52%) than participants in the other data sources (22%-25%), be older than 50 years of age (29% vs. 5%-10%), and report multiple races (12% vs. 3%-5%). The NHBS-IDU1 population resembled persons using the downtown needle exchange in age and race distribution. An examination of cross-group recruitment frequencies in NHBS-IDU1 suggested barriers to recruitment across different areas of residence, races, and drugs most frequently injected.

CONCLUSIONS

The substantial differences in age and area of residence between NHBS-IDU1 and the other data sources suggest that RDS may not have accessed the full universe of Seattle area injection networks. Further empirical data are needed to guide the evaluation of RDS-generated samples.

High rates of midazolam injection among drug users in Bangkok, Thailand

Background

Reports from Thailand suggest that a growing number of people who inject drugs (IDU) are now injecting midazolam, a legal benzodiazepine with potent amnestic and ventilatory depressant effects. We therefore sought to examine midazolam injection among a community-recruited sample of Thai IDU.

Methods

We examined the prevalence and correlates of midazolam injection among 252 IDU participating in the Mitsampan Community Research Project, Bangkok, using multivariate logistic regression. We also examined the use of midazolam in combination with other drugs.

Results

252 IDU participated in this study, including 66 (26.2%) women. In total, 170 (67.5%) participants reported ever having injected midazolam, and 144 (57.1%) reported daily midazolam injection in the past six months. In multivariate analyses, a history of midazolam injection was independently associated with using drugs in combination (adjusted odds ratio [AOR] = 5.86; 95% confidence interval [CI]: 2.96-11.60), younger age (AOR = 0.43; 95%CI: 0.22-0.83), having a history of methadone treatment (AOR = 3.12, 95%CI: 1.55-6.90), and binge drug use (AOR = 2.25, 95%CI: 1.09-4.63). The drugs most commonly used in combination with midazolam were heroin (72.3%) and yaba (methamphetamine) (30.5%).

Conclusion

We observed a high rate of midazolam injection among Thai IDU. Midazolam injection was strongly associated with polysubstance use and binge drug use, and was most commonly used in combination with both opiates and methamphetamines. Our findings suggest that midazolam injection has become increasingly common within Thailand. Evidence-based approaches for reducing harms associated with midazolam injection are needed.

Meth/amphetamine use and associated HIV: Implications for global policy and public health

Amphetamine type stimulants (ATS) have become the focus of increasing attention worldwide. There are understandable concerns over potential harms including the transmission of HIV. However, there have been no previous global reviews of the extent to which these drugs are injected or levels of HIV among users. A comprehensive search of the international peer-reviewed and grey literature was undertaken. Multiple electronic databases were searched and documents and datasets were provided by UN agencies and key experts from around the world in response to requests for information on the epidemiology of use. Amphetamine or methamphetamine (meth/amphetamine, M/A) use was documented in 110 countries, and injection in 60 of those. Use may be more prevalent in East and South East Asia, North America, South Africa, New Zealand, Australia and a number of European countries. In countries where the crystalline form is available, evidence suggests users are more likely to smoke or inject the drug; in such countries, higher levels of dependence may be occurring. Equivocal evidence exists as to whether people who inject M/A are at differing risk of HIV infection than other drug injectors; few countries document HIV prevalence/incidence among M/A injectors. High risk sexual behaviour among M/A users may contribute to increased risk of HIV infection, but available evidence is not sufficient to determine if the association is causal. A range of possible responses to M/A use and harm are discussed, ranging from supply and precursor control, to demand and harm reduction. Evidence suggests that complex issues surround M/A, requiring novel and sophisticated approaches, which have not yet been met with sufficient investment of time or resources to address them. Significant levels of M/A in many countries require a response to reduce harms that in many cases remain poorly understood. More active models of engagement with M/A users and provision of services that meet their specific needs are required.

Drug use patterns among Thai illicit drug injectors amidst increased police presence

Thailand has traditionally pursued an aggressive enforcement-based anti-illicit drug policy in an effort to make the country "drug-free." In light of this ongoing approach, we sought to assess impacts of enforcement on drug use behaviors among a cohort of injection drug users (IDU) in Thailand. We examined drug use patterns among IDU participating in a cross-sectional study conducted in Bangkok (n = 252). Participants were asked to provide data regarding patterns of drug use in the previous six months, including types of drugs consumed, method of consumption, frequency of use, and weekly income spent on drugs. We also conducted bivariate analyses to identify a possible effect of a reported increase in police presence on measures of drug use and related risk behaviors among study participants. One hundred fifty-five (61.5%) individuals reported injection heroin use and 132 (52.4%) individuals reported injection midazolam use at least daily in the past six months. Additionally, 86 (34.1%) individuals reported at least daily injection Yaba and Ice (i.e., methamphetamine) use. Participants in our study reported high levels of illicit drug use, including the injection of both illicit and licit drugs. In bivariate analyses, no association between increased police presence and drug use behaviors was observed. These findings demonstrate high ongoing rates of drug injecting in Thailand despite reports of increased levels of strict enforcement and enforcement-related violence, and raise questions regarding the merits of this approach.

Prevalence of hepatitis B, tetanus, hepatitis A, human immunodeficiency virus and feasibility of vaccine delivery among injecting drug users in Bangkok, Thailand, 2003-2005

OBJECTIVES

To estimate the prevalence of hepatitis B virus (HBV), tetanus, hepatitis A virus (HAV) and human immunodeficiency virus (HIV) in injecting drug users (IDUs), risk factors associated with infection and the feasibility of HBV vaccine delivery in HBV seronegatives.

METHODS

Cross-sectional seroprevalence survey of 1535 IDUs recruited from 17 Bangkok Metropolitan Administration (BMA) methadone clinics and HBV vaccination of seronegatives.

RESULTS

Prevalence of antibody to HBV, tetanus, HAV and HIV was 87.8%, 68.1%, 60.2% and 35.9%, respectively. Prevalence of HBV and HAV increased with increasing age; prevalence of tetanus decreased with increasing age. Being HIV seropositive was related inversely to income and being tetanus seronegative. Of the 189 HBV seronegative IDUs, 81.0% completed the vaccine series. IDUs with HIV had a 6.5-fold odds of vaccine non-response.

CONCLUSIONS

These data underscore the need for, and feasibility of, vaccine delivery in this population and support targeting efforts at high-risk age groups.

Using respondent-driven sampling methodology for HIV biological and behavioral surveillance in international settings: a systematic review

To determine operational and analytical characteristics of respondent-driven sampling (RDS) in international settings and to explore factors that may affect recruitment of most-at-risk populations using RDS, we reviewed HIV biological and behavioral surveillance studies that used this method outside of the United States. We identified 123 eligible studies, 59 from Europe, 40 from Asia and the Pacific, 14 from Latin America, seven from Africa and three from Oceania. Studies collectively recruited 32,298 participants between 2003 and 2007; 53% of studies were conducted among injecting drug users, which generally had faster recruitment compared with studies among sex workers. All but 13 studies reached > or = 90% of their intended sample size, and six studies failed to reach equilibrium for key variables. This review has shown that RDS is an effective technique, when designed and implemented appropriately, to sample most-at-risk populations for HIV biological and behavioral surveys.