Monday, October 31, 2011

Heterosexual HIV/AIDS Prevalent In Low Income Areas More than Rich

Heterosexual HIV/AIDS Prevalent In Low Income Areas More than Rich

Editor's Choice
Main Category: HIV / AIDS
Article Date: 12 Aug 2011 - 10:00 PDT

The review of a major national population HIV study has found that the HIV infection rate among low-income heterosexuals in 24 American cities with a high prevalence of AIDS is 10 to 20 times greater than in the general U.S. population.

    RDS - Recruitment of People with Small Injecting Networks

    AIDS Behav. 2011 Aug 27. [Epub ahead of print]
    Respondent-Driven Sampling and the Recruitment of People with Small Injecting Networks.
    Paquette D, Bryant J, de Wit J.
    SourceNational Centre in HIV Social Research, University of New South Wales, Webster Building, Sydney, NSW, 2052, Australia,

    Respondent-driven sampling (RDS) is a form of chain-referral sampling, similar to snowball sampling, which was developed to reach hidden populations such as people who inject drugs (PWID). RDS is said to reach members of a hidden population that may not be accessible through other sampling methods. However, less attention has been paid as to whether there are segments of the population that are more likely to be missed by RDS. This study examined the ability of RDS to capture people with small injecting networks. A study of PWID, using RDS, was conducted in 2009 in Sydney, Australia. The size of participants' injecting networks was examined by recruitment chain and wave. Participants' injecting network characteristics were compared to those of participants from a separate pharmacy-based study. A logistic regression analysis was conducted to examine the characteristics independently associated with having small injecting networks, using the combined RDS and pharmacy-based samples. In comparison with the pharmacy-recruited participants, RDS participants were almost 80% less likely to have small injecting networks, after adjusting for other variables. RDS participants were also more likely to have their injecting networks form a larger proportion of those in their social networks, and to have acquaintances as part of their injecting networks. Compared to those with larger injecting networks, individuals with small injecting networks were equally likely to engage in receptive sharing of injecting equipment, but less likely to have had contact with prevention services. These findings suggest that those with small injecting networks are an important group to recruit, and that RDS is less likely to capture these individuals.

    PMID: 21874352 [PubMed - as supplied by publisher]

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    HIV Risk Behaviours and their Relationship to Intimate Partner Violence (IPV) Among Men Who Have Multiple Female Sexual Partners in Cape Town, South Africa

    Authors: Townsend, Loraine1; Jewkes, Rachel2; Mathews, Catherine3; Johnston, Lisa4; Flisher, Alan5; Zembe, Yanga3; Chopra, Mickey6

    Source: AIDS and Behavior, Volume 15, Number 1, January 2011 , pp. 132-141(10)

    Publisher: Springer


    HIV/AIDS and intimate partner violence (IPV) are growing public health concerns in South Africa. Knowledge about adult men's perpetration of IPV and links between HIV risk behaviours and IPV is limited. Respondent driven sampling was used to recruit men who have multiple concurrent female sexual partners. Forty-one percent of the 428 recruited men had perpetrated IPV. Inconsistent condom use was associated with physical IPV; experiencing a symptom of a sexually transmitted infection and engaging in transactional sex were associated with physical and sexual IPV; problem alcohol use was associated with physical, and any IPV, but not sexual IPV; having five or more partners was associated with sexual IPV; perceptions of partners' infidelity were associated with physical and any IPV. HIV risk reduction interventions among men, especially those with multiple female sex partners, should incorporate strategies to change the underlying construction of masculinity that combines the anti-social and risky behaviours of IPV perpetration, inconsistent condom use, transactional sex and heavy alcohol consumption.

    Keywords: Concurrent sexual partnerships; HIV prevention; High risk heterosexual men; Intimate partner violence; Respondent driven sampling; South Africa

    Document Type: Research article

    DOI: 10.1007/s10461-010-9680-5

    Affiliations: 1: Health Systems Research Unit, Medical Research Council, P.O. Box 19070, Tygerberg 7505, Cape Town, South Africa, Email: 2: Gender and Health Research Unit, Medical Research Council, Pretoria, South Africa 3: Health Systems Research Unit, Medical Research Council, P.O. Box 19070, Tygerberg 7505, Cape Town, South Africa 4: School of Public Health and Tropical Medicine, Tulane University, New Orleans, LA, USA 5: Division of Child and Adolescent Psychiatry and Adolescent Health Research Unit, University of Cape Town, Cape Town, South Africa 6: United Nations Childrens Fund, New York, NY, USA

    Publication date: 2011-01-01

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    Yanga Zembe1, Loraine Townsend1, Cathy Mathews1, Mickey Chopra1, Anna
    Mia Ekstrom2, Anna Thorson2, Susanne Stromdahl2, Heidi O’Bra3
    1 Medical Research Council, Cape Town, South Africa
    2 IHCAR, Karolinska Institute, Sweden
    3 US Centers for Disease Control and Prevention/Global AIDS Program,
    Pretoria, South Africa.

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    The sensitivity of respondent-driven samplingXin Lu1, Linus Bengtsson2, Tom Britton3, Martin Camitz4, Beom Jun Kim5, Anna Thorson6, Fredrik Liljeros7Article first published online: 18 JUL 2011

    DOI: 10.1111/j.1467-985X.2011.00711.x

    Keywords:Directed network;Hidden population;Network;Respondent-driven sampling;Sampling;Sensitivity

    Summary. Researchers in many scientific fields make inferences from individuals to larger groups. For many groups, however, there is no list of members from which to draw a random sample. Respondent-driven sampling (RDS) is a relatively new sampling methodology that circumvents this difficulty by using the social networks of the groups under study. The RDS method has been shown to provide unbiased estimates of population proportions given certain conditions. The method is now widely used in human immunodeficiency virus related studies among high risk populations globally. We test the RDS methodology by simulating RDS studies on the social networks of a large Lesbian, gay, bisexual and transgender Web community. The robustness of the RDS method is tested by violating, one by one, the conditions under which the method provides unbiased estimates. Simulations indicate that the bias is large if networks are directed or respondents choose to invite people on the basis of characteristics that are correlated with the study outcomes. The bias and variance increase if participants invite close as opposed to more distant friends whereas sampling in denser networks sharply reduces variance. However, the RDS method shows strong resistance to sampling without replacement, low response rates and certain errors in the participants’ reporting of their network sizes, as well as the selection criteria of seeds. The effects of network structure and the number of seeds and coupons are also discussed.

    A novel application of respondent-driven sampling to evaluate effectiveness of a multi-level intervention using a cluster randomized trial: design of the DOST trial

    S.S. Solomon1, S.H. Mehta2, F. Sifakis2, A.K. Srikrishnan1, S. Solomon1, D.D. Celentano2

    1YRG Centre for AIDS Research and Education, Chennai, India, 2Johns Hopkins Bloomberg School of Public Health, Baltimore, United States

    The impact of voluntary, counseling and testing (VCT) on risk-behavior and linkage to care is well established. Despite widespread availability in India (>1000 VCT centers), utilization among most-at-risk-populations (e.g., men who have sex with men [MSM]) remains low. We propose a novel application of respondent-driven sampling (RDS) to implement and evaluate the effectiveness of multi-level intervention to increase VCT utilization among MSM in south India using a cluster-randomized trial design.

    We aim to evaluate the effectiveness of gay-friendly men's wellness centers (DOST Centers) on behavior change at the community-, network- and individual-levels in south India. Key challenges in the conduct of cluster-randomized trials are: 1) ensuring generalizability of the study population; 2) prevention of overlap between intervention and control clusters (contamination); and 3) evaluating impact at multiple levels.

    We propose to leverage an established sampling strategy for hidden populations (RDS) to address these challenges. First, cross-sectional RDS surveys will be conducted in intervention and control communities prior to and 2 years after the establishment of DOST centers to assess community-level effectiveness of the intervention. Through weighting, RDS estimates can approximate underlying population estimates. Second, we will use RDS network information from the baseline RDS to identify discrete communities for randomization and disseminate information on DOST centers. Running concurrent RDS samples will allow us to identify/eliminate overlap in real time; disseminating information through discrete networks will optimize network relationships. Third, the evaluation RDS will allow evaluation of network-level impact using RDS process indicators and individual-level impact by comparison of participants who did and did not visit DOST centers in intervention communities.

    We propose this novel application of RDS to address key challenges in the implementation of cluster-randomized trials and evaluation of intervention effectiveness. With increasing focus on implementation science, the DOST trial design can easily be adapted to other settings/populations.

    Possible increase in HIV and syphilis prevalence among men who have sex with men in Guangzhou, China: results from a respondent-driven sampling survey.

    Zhong F, Lin P, Xu H, Wang Y, Wang M, He Q, Fan L, Li Y, Wen F, Liang Y, Raymond HF, Zhao J.
    SourceGuangzhou Municipal Center for Disease Control and Prevention, 510080, Guangzhou, China.

    A respondent-driven sampling survey was conducted to investigate HIV related serological and behavioral characteristics of men who have sex with men (MSM) in Guangzhou, China, and to identify associated factors potentially driving the epidemic. Respondent-Driven Sampling Analysis Tool and SPSS were used to generate adjusted estimates and to explore associated factors. Three hundred seventy-nine eligible participants were recruited. The adjusted prevalence of HIV and current syphilis infection are 5.2% and 17.5% respectively. 60.3% have unprotected anal sex in the past 6 months. Unprotected anal sex, having receptive anal sex and current syphilis infection are significant factors associated with HIV infection. The potential for a rapid rise of HIV and syphilis infections among MSM in Guangzhou exists. Targeted interventions with voluntary counseling and testing (VCT) and sexually transmitted infection (STI) services are needed to address the epidemic, with a focus on such subgroups as those of with current syphilis, and non-official Guangzhou residence status.

    Respondent-driven sampling to recruit MDMA users: A methodological assessment.

    Drug and Alcohol Dependence 78(2):147-157, May 2005. Jichuan Wang, Robert G. Carlson, Russel S. Falck, Harvey A. Siegal, Ahmmed Rahman, and Linna Li.

    Recruiting more representative samples of illicit drug users is a continuing challenge in substance abuse research. Respondent-driven sampling (RDS), a new form of chain-referral sampling, is designed to eliminate the bias caused by the non-random selection of the initial recruits and reduce other sources of bias, such as bias due to voluntarism and masking, that are usually associated with regular chain-referral sampling. This study assessed the application of RDS among young adult users of 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") and found that the sample compositions converged to equilibrium within a limited number of recruitment waves, independent of the characteristics of the initial "seed" recruits. The sample compositions approximated the theoretical equilibrium compositions, and were not significantly different from the estimated population compositions, except that white respondents were over-sampled and black respondents were under-sampled. The effect of voluntarism and masking on the sampling process was not significant. Though identifying productive seeds and improving the referral rate are significant challenges when implementing RDS, the results show that RDS is a flexible and robust sampling method with the potential to be widely used in studies of illicit drug-using populations.

    NIAAA Glossary Terms: illicit drug, AOD user, sample selection, sampling bias, research issue, MDMA, racial differences, White, Black, intervention referral, human study

    Respondent-driven sampling on the Thailand-Cambodia border. I. Can malaria cases be contained in mobile migrant workers?

    Submitted by patrick sampao on May 11, 2011 - 12:33
    Tags: Cambodiamalariamigrant workersThailand
    Author(s): Amnat Khamsiriwatchara, Piyaporn Wangroongsarb, Julie Thwing, James Eliades, Wichai Satimai, Charles Delacollette, Jaranit Kaewkungwal
    Reference: Malaria Journal 2011, 10:120 (10 May 2011)
    Access: Click here to go to the full article
    Contact email:

    Reliable information on mobility patterns of migrants is a crucial part of the strategy to contain the spread of artemisinin-resistant malaria parasites in South-East Asia, and may also be helpful to efforts to address other public health problems for migrants and members of host communities. In order to limit the spread of malarial drug resistance, the malaria prevention and control programme will need to devise strategies to reach cross-border and mobile migrant populations.

    The Respondent-driven sampling (RDS) method was used to survey migrant workers from Cambodia and Myanmar, both registered and undocumented, in three Thai provinces on the Thailand-Cambodia border in close proximity to areas with documented artemisinin-resistant malaria parasites. 1,719 participants (828 Cambodian and 891 Myanmar migrants) were recruited. Subpopulations of migrant workers were analysed using the Thailand Ministry of Health classification based on length of residence in Thailand of greater than six months (long-term, or M1) or less than six months (short-term, or M2). Key information collected on the structured questionnaire included patterns of mobility and migration, demographic characteristics, treatment-seeking behaviours, and knowledge, perceptions, and practices about malaria.

    Workers from Cambodia came from provinces across Cambodia, and 22% of Cambodian M1 and 72% of Cambodian M2 migrants had been in Cambodia in the last three months. Less than 6% returned with a frequency of greater than once per month. Of migrants from Cambodia, 32% of M1 and 68% of M2 were planning to return, and named provinces across Cambodia as their likely next destinations. Most workers from Myanmar came from Mon state (86%), had never returned to Myanmar (85%), and only 4% stated plans to return.

    Information on migratory patterns of migrants from Myanmar and Cambodia along the malaria endemic Thailand-Cambodian border within the artemisinin resistance containment zone will help target health interventions, including treatment follow-up and surveillance.

    Respondent Driven Sampling Blog

    Respondent Driven Sampling Blog has been setup for researchers using respondent driven sampling methods for their research projects. To create a platform to share their experience or needs to setup a research surveillance site and what systems to put in place to:

          • Recruit Participants
          • Invite Coupons
          • E-Invites
          • Screen Participants
          • Manage Research
          • Data Collection Methods
          • Electronic Questionnaires
          • Audio Questionnaires
          • Incentive Management
    There are many researchers who have used this method over the years since RDS was developed by Douglas Heckathorn more than a decade ago, in 1997, as part of a National Institute on Drug Abuse-funded HIV-prevention research project targeting drug injectors in several Connecticut cities. RDS served as the recruitment mechanism for an intervention design developed with Robert Broadhead termed "peer-driven intervention" (PDI). So we are putting together a database of RDS related publications as a reference tool for researchers. If you would like to share yours, please submit them to the Blog.

    Antiretroviral Drug Resistance in a Respondent-Driven Sample of HIV-Infected Men Who Have Sex With Men in Brazil

    Authors:Bermúdez-Aza, Elkin Hernan MD, MSc; Kerr, Ligia Regina Franco Sansigolo MD, PhD; Kendall, Carl PhD; Pinho, Adriana Araujo MSc; de Mello, Maeve Brito PhD; Mota, Rosa Salani MSc; Guimarães, Mark Drew Crosland PhD; Alencar, Cecilia Salete MSc; de Brito, Ana Maria PhD; Dourado, Ines Costa PhD; da Batista, Sonia Maria Batista MSc; Abreu, Fabiano BSc; de Oliveira, Lisangela Cristina MSc; de Souza Moraes, Adão MSc; Benzaken, Adele Schwartz MD, PhD; Merchan-Hamann, Edgar MD, PhD; de Freitas, Gisele Maria Brandão MD, MSc; McFarland, Willi MD, PhD; Albuquerque, Elizabeth PhD; Rutherford, George W MD, MSc; Sabino, Ester MD, PhD

    Background: There are few studies on HIV subtypes and primary and secondary antiretroviral drug resistance (ADR) in community-recruited samples in Brazil. We analyzed HIV clade diversity and prevalence of mutations associated with ADR in men who have sex with men in all five regions of Brazil.

    Methods: Using respondent-driven sampling, we recruited 3515 men who have sex with men in nine cities: 299 (9.5%) were HIV-positive; 143 subjects had adequate genotyping and epidemiologic data. Forty-four (30.8%) subjects were antiretroviral therapy-experienced (AE) and 99 (69.2%) antiretroviral therapy-naïve (AN). We sequenced the reverse transcriptase and protease regions of the virus and analyzed them for drug resistant mutations using World Health Organization guidelines.

    Results: The most common subtypes were B (81.8%), C (7.7%), and recombinant forms (6.9%). The overall prevalence of primary ADR resistance was 21.4% (i.e. among the AN) and secondary ADR was 35.8% (i.e. among the AE). The prevalence of resistance to protease inhibitors was 3.9% (AN) and 4.4% (AE); to nucleoside reverse transcriptase inhibitors 15.0% (AN) and 31.0% (AE) and to nonnucleoside reverse transcriptase inhibitors 5.5% (AN) and 13.2% (AE). The most common resistance mutation for nucleoside reverse transcriptase inhibitors was 184V (17 cases) and for nonnucleoside reverse transcriptase inhibitors 103N (16 cases).

    Conclusions: Our data suggest a high level of both primary and secondary ADR in men who have sex with men in Brazil. Additional studies are needed to identify the correlates and causes of antiretroviral therapy resistance to limit the development of resistance among those in care and the transmission of resistant strains in the wider epidemic.

    Network Model-Assisted Inference from Respondent-Driven Sampling Data

    Authors: Krista J. Gile, Mark S. Handcock

    (Submitted on 1 Aug 2011)

    Abstract: Respondent-Driven Sampling is a method to sample hard-to-reach human populations by link-tracing over their social networks. Beginning with a convenience sample, each person sampled is given a small number of uniquely identified coupons to distribute to other members of the target population, making them eligible for enrollment in the study. This can be an effective means to collect large diverse samples from many populations.

    Inference from such data requires specialized techniques for two reasons. Unlike in standard sampling designs, the sampling process is both partially beyond the control of the researcher, and partially implicitly defined. Therefore, it is not generally possible to directly compute the sampling weights necessary for traditional design-based inference. Any likelihood-based inference requires the modeling of the complex sampling process often beginning with a convenience sample. We introduce a model-assisted approach, resulting in a design-based estimator leveraging a working model for the structure of the population over which sampling is conducted.

    We demonstrate that the new estimator has improved performance compared to existing estimators and is able to adjust for the bias induced by the selection of the initial sample. We present sensitivity analyses for unknown population sizes and the misspecification of the working network model. We develop a bootstrap procedure to compute measures of uncertainty. We apply the method to the estimation of HIV prevalence in a population of injecting drug users (IDU) in the Ukraine, and show how it can be extended to include application-specific information.

    Comments: 38 pages, 11 figures, under review. Includes supplemental materials

    Subjects: Methodology (stat.ME)

    Cite as: arXiv:1108.0298v1 [stat.ME]

    Putting Respondent-Driven Sampling on the Map: Insights from Rio de Janeiro, Brazil

    Putting Respondent-Driven Sampling on the Map: Insights from Rio de Janeiro, Brazil

    Toledo, Lidiane MPH; Codeço, Cláudia T PhD; Bertoni, Neilane MPH; Albuquerque, Elizabeth MPH; Malta, Monica MPH, PhD; Bastos, Francisco I MD, PhD; on behalf of the Brazilian Multicity Study Group on Drug Misuse


    Background: Hard-to-reach populations with high background infection rates for HIV are particularly relevant in countries with restricted HIV epidemics, such as Brazil, where the very dynamics of the epidemic depends on the bridges between those populations and the general population. Respondent-driven sampling (RDS) has been one of the key strategies to assess such populations and inform policy making.

    Objectives: To geocode and visualize an RDS-based study on 605 heavy drug users, conducted in Rio de Janeiro, in 2009.

    Methods: The location and characteristics of the residence of interviewees were collected by an Audio Computer-Assisted Self Interview (ACASI) survey, supplemented by additional information. Place of residence was geocoded and depicted as network graphs and thematic maps.

    Results: The geographic distribution of the interviewees was found to be very heterogeneous. The recruiting chains progressed slowly during the successive waves toward neighborhoods far from the initial geographic axis. Despite the undeniable progress toward a broader geographic scope as the study proceeded through 11 successive waves, some key geographic areas were excluded.

    Conclusions: In the context of a large and complex urban area, plagued by structural violence and with a lively drug scene, the study made evident network bottlenecks. Either secondary to its relatively small sample size, structural constraints, or a combination of both, such bottlenecks represent a formidable challenge for RDS or other network-based methods as applied to urban settings with characteristics similar to Rio de Janeiro.

    read more
    Respondent Driven Sampling Blog has been setup for researchers using respondent driven sampling methods for their research projects. To create a platform to share their experience or needs to setup a research surveillance site and what systems to put in place to:
          • Recruit Participants
          • Barcode Invite Coupon Generator
          • E-Invites
          • Screen Participants
          • Manage Research
          • Data Collection Methods
          • Electronic Questionnaires
          • Audio Questionnaires
          • Incentive Management
    There are many researchers who have used this method over the years since RDS was developed by Douglas Heckathorn more than a decade ago, in 1997, as part of a National Institute on Drug Abuse-funded HIV-prevention research project targeting drug injectors in several Connecticut cities. RDS served as the recruitment mechanism for an intervention design developed with Robert Broadhead termed "peer-driven intervention" (PDI). So we are putting together a database of RDS related publications as a reference tool for researchers. If you would like to share yours, please submit them to the Blog. for more information on a site management system.

    Thursday, August 19, 2010

    Respondent Driven Sampling

    I have set up this blog site to connect with researchers using respondent driven sampling (RDS). It is a forum for researchers who use the RDS method to discuss issues and challenges around setting up a study site to recruit participants and to collect the data. Having managed a RDS research site I found the method used to capture the data time consuming and prone to errors as the number of participants increased. This led to the development of  BRYANT Research Systems.

    Since 2008 we have worked to develop tools to simplify the setting up of respondent driven sampling (RDS) research sites to ensure integrity of the data captured. The system is web-based and provides the ability for a researcher to manage the data and performance of the research site online. All data collected is RDSAT compatible.

    We have created a unique automated serial numbering system. The system helps to simplify eligibility screening of participants and links a social network via the serial number. The system prints or e-mails the invitation coupons with a serial number and allows the number to be scanned into the data base to capture the required data for your research.
    Features of the BRYANT System:
    Capture Participants
    Print Serial Number
    E-mail Serial Number
    Screen Eligibility
    Electronic Questionnaires
    Audio Questionnaires
    Incentive Management
    Data Capturing
    Data Management
    Off Site Monitoring