ORIGINAL PAPER Using Respondent-Driven Sampling Methodology for HIV Biological and Behavioral Surveillance in International Settings: A Systematic Review Mohsen Malekinejad Æ Lisa Grazina Johnston Æ Carl Kendall Æ Ligia Regina Franco Sansigolo Kerr Æ Marina Raven Rifkin Æ George W. Rutherford Published online: 17 June 2008 Ó Springer Science+Business Media, LLC 2008 Abstract To determine operational and analytical char- acteristics 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 C90% 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. Keywords HIV/AIDS Á Most at risk populations Á Respondent-driven sampling Á Biological and behavioral surveillance Introduction With 33.2 million people worldwide currently infected, and with 2.1 million deaths in 2007 alone, the HIV pandemic is one of the most significant public health challenges of the 21st century (UNAIDS 2007). In most countries, the HIV epidemic is driven by sub-populations at highest risk (termed ‘‘most-at-risk populations’’) for becoming infected with or transmitting HIV (UNAIDS/WHO Working Group on Glo- bal HIV/AIDS and STI Surveillance 2000). In two types of epidemic, low-level (prevalence of infection is\ 5% in most- at-risk populations) and concentrated (prevalence is [ 5% in most-at-risk populations but is not yet [ 1% in the general population) these most-at-risk populations include injecting drug users (IDUs), men who have sex with men (MSM), and sex workers (SWs) along with their sexual partners, as well as displaced populations, migrant workers, long-distance truck drivers, and youth (Mills et al. 2004). Even in gen- eralized epidemics, in which prevalence is [ 1% in pregnant women attending antenatal clinics, there is recognition that risk is not uniformly distributed within populations and is driven, at least initially, by most-at-risk populations that bridge HIV to the lower-risk general population (Chopra et al. 2007; Doherty et al. 2006; Gregson et al. 2002; Hal- perin and Epstein 2004). Accurate HIV data on incidence and prevalence and associated behavioral data from most-at-risk populations are M. Malekinejad School of Public Health, University of California, Berkeley, Berkeley, CA, USA M. Malekinejad (&) Á M. R. Rifkin Á G. W. Rutherford Global Health Sciences, University of California, San Francisco, 50 Beale Street, Suite 1200, San Francisco, CA 94105-1823, USA e-mail: mmalekinejad@psg.ucsf.edu L. G. Johnston Á C. Kendall School of Public Health and Tropical Medicine, Tulane University, New Orleans, LA, USA C. Kendall College of Health and Social Services, New Mexico State University, Las Cruces, NM, USA L. R. F. S. Kerr Faculty of Medicine, Federal University of Ceara ´, Fortaleza, Ceara ´, Brazil 123 AIDS Behav (2008) 12:S105–S130 DOI 10.1007/s10461-008-9421-1