Respondent-driven sampling: Advantages and disadvantages from a sampling method

This article summarizes the main elements, advantages, and disadvantages of Respondent-driven Sampling (RDS). Some criticisms regarding the feasibility of the inherent assumptions, their point estimators, and the obtained variances are pointed out. This article also comments on the problems observed in the quality of reports. Surveys using RDS should be methodologically sound as they are being applied to define priorities in health programs and develop national and international policies for financing service delivery, among other uses. However, there is considerable potential for bias related to implementation and analytical errors. There is limited empirical evidence on how representative the results obtained by RDS are, and the quest to improve the methodology is still in progress. Nevertheless, to have confidence in RDS results, we must verify that the social structure of the networks conforms to the assumptions required by the theory, that the sampling assumptions are reasonably fulfilled, and that the quality of the report is optimal, particularly for methodological and analytical items.

HIV surveillance and research for migrant populations: a protocol integrating respondent-driven sampling, case finding, and medicolegal services for Venezuelans living in Colombia (Preprint)

BACKGROUND Epidemiologic research among migrant populations is limited by logistical, methodological, and ethical challenges, but necessary for informing public health and humanitarian programming. OBJECTIVE We describe a methodology to estimate HIV prevalence among Venezuelan migrants in Colombia. METHODS Respondent-driven sampling (RDS), a non-probability sampling method, was selected for attributes of reaching highly networked populations without sampling frames and analytic methods that permit estimation of population parameters. RDS was modified to permit electronic referral of peers via SMS and Whatsapp. Participants complete socio-behavioral surveys and rapid HIV and syphilis screening tests with confirmatory testing. HIV treatment is not available for migrants who have entered Colombia through irregular pathways; thus, medicolegal services integrated into post-test counseling provide staff lawyers and legal assistance to participants diagnosed with HIV or syphilis for sustained access to treatment through the national health system. Case finding is integrated into RDS to allow partner referral. The study is implemented by a local community-based organization providing HIV support services and related legal services for Venezuelans in Colombia. RESULTS Data collection launched in four cities in July and August 2021. As of November 2021, 3,105 of the target 6,100 participants were enrolled. CONCLUSIONS Tailored methods that combine community-led efforts with innovations in sampling and linkage to care can aid in advancing health research for migrant and displaced populations. Worldwide trends in displacement and migration underscore the value of improved methods for translation to humanitarian and public health programming.

The use of respondent‑driven sampling to assess febrile illness treatment-seeking behaviours among forest-goers in Cambodia and Vietnam

Background Countries in the Greater Mekong sub-region (GMS) aim to eliminate all forms of malaria by 2030. In Cambodia and Vietnam, forest-goers are at an increased risk of malaria. Universal access to prompt diagnosis and treatment is a core malaria intervention. This can only be achieved by understanding the healthcare-seeking behaviour among the most vulnerable groups and eliminating barriers to prompt and effective treatment. This study aimed to explore healthcare-seeking behaviours for febrile illness among populations at risk for malaria in Cambodia and Vietnam. Methods In 2019, researchers from Population Services International (PSI) conducted a population-based survey of forest-goers in Cambodia and Vietnam using respondent-driven sampling (RDS) In Cambodia two operational districts, Oral and Phnom Srouch in Kampong Speu Province were included in the study. In Vietnam, communes located within 15 km of the forest edge in Binh Phuoc and Gia Lai Provinces were selected. Adults who had spent at least one night per week or four nights per month in the forest over the previous three months were eligible for the study. Results Some 75% of forest-goers in Cambodia and 65% in Vietnam sought treatment for illness outside the home. In Cambodia, 39% sought treatment from the private sector, 32% from community health workers, and 24% from public health facilities. In Vietnam, 62% sought care from community facilities, 29.3% from the private sector, and 6.9% went to a public facility. Among forest-goers who sought care, 33% in Cambodia and 52% in Vietnam did so within 24 h. Conclusions This study is consistent with others that show that early diagnosis and treatment of malaria remains an obstacle to malaria elimination. This study also demonstrates that there are gaps in timeliness of care seeking among forest-goers. The findings from this study around provider preference and delays in treatment-seeking can be used to strengthen the design and targeting of malaria interventions and social and behaviour change strategies to accelerate malaria elimination in Cambodia and Vietnam.

Using large-scale respondent driven sampling to monitor the end of an HIV epidemic among persons who inject drugs in Hai Phong, Viet Nam

Aims To describe the use of large-scale respondent driven sampling (RDS) surveys to demonstrate the “end of an HIV epidemic” (HIV incidence < 0.5/100 person-years) among persons who inject drugs (PWID) in a middle-income country. Large sample sizes are needed to convincingly demonstrate very low incidence rates. Methods 4 large surveys (Ns approximately 1500 each) were conducted among PWID in Hai Phong, Vietnam in 2016–2019. Respondent driven sampling (RDS) with a modification to add snowball sampling was used for recruiting participants. HIV incidence was measured through recency testing, repeat participants across multiple surveys and in a cohort study of PWID recruited from the surveys. RDS analytics (time to equilibria and homophilies for major variables) were used to assess similarities/differences in RDS only versus RDS plus snowball recruiting. Characteristics were compared among respondents recruited through standard RDS recruitment versus through snowball sampling. An overall assessment of the robustness of RDS to modification was made when adding a snowball sampling recruitment. Results RDS recruiting was very efficient in the first 5 weeks of each survey with approximately 180 respondents recruited per week. Recruiting then slowed considerably, and snowball sampling (permitting an individual respondent to recruit large numbers of new respondents) was added to the existing RDS recruiting. This led to recruiting within 13–14 weeks of 1383, 1451, 1444 and 1268 respondents, close to the target of 1500 respondents/survey. Comparisons of participants recruited through standard RDS method and respondents recruited through snowball methods showed very few significant differences. RDS analytics (quickly reaching equilibria, low homophilies) were favorable for both RDS recruited and total numbers of participants in each survey. DRug use and Infections in ViEtnam (DRIVE) methods have now been officially adopted in other provinces. Conclusions RDS appears to be quite robust with respect to adding a modest number of participants recruited through snowball sampling. Large sample sizes can provide compelling evidence for “ending an HIV epidemic” to policy makers in a PWID population in a middle income country setting.

Exploração sexual de crianças e adolescentes em situação de rua no Sul do Brasil

Resumo O objetivo do estudo foi investigar a prevalência de exploração sexual entre crianças e adolescentes em situação de rua e as características associadas a este desfecho. Neste estudo transversal, conduzido nos municípios de Rio Grande e Porto Alegre-RS, os dados foram coletados por meio de entrevistas com os participantes, as quais foram conduzidas por entrevistadores treinados. O método de amostragem foi o Respondent-Driven Sampling (RDS) e as análises estatísticas foram conduzidas por meio da regressão de Poisson com ajuste robusto da variância. A amostra foi composta por 186 crianças e adolescentes com idades entre 10 e 17 anos, das quais 8% relataram ter tido experiência de exploração sexual. Ter idade entre 16 e 17 anos, ter sofrido relação sexual forçada e não ter vínculo escolar foram características independentemente associadas a este desfecho. Foi observada que a falta de vínculo escolar aumentou em 16 vezes a probabilidade de sofrer exploração sexual, sendo o principal fator de risco identificado neste estudo. Sugere-se que a inclusão e permanência das crianças e adolescentes em situação de rua no contexto escolar possa reduzir significativamente o risco de exploração sexual entre esta população.