Time-space, venue-based sampling of migrant populations

Background: Developing interventions for early detection and treatment of diseases among high-risk groups, such as migrants,immigrants, and refugees requires high-quality data on prevalence of behaviors, health conditions, and health outcomes. Projects that use probability sampling methods, such as household surveys of these populations are important.Probabilitysampling of these populations is challenging;unknown sampling frames and distributions. Time-space sampling (TSS) (also known as time-location sampling or as venue-based sampling) is a probability-based sampling method of defined populations congregating at specific locations and times. Methods: We describe TSS in terms of procedures, advantages, and disadvantages of TSS and build on the collective TSS experience with hidden non-migrant populations, particularly persons at risk for infection with blood-borne pathogens and sexually transmitted infections. We highlight factors that can enhance successful application of TSS in three different sampling phases (pre-sampling, during sampling, and post-sampling) of migrant populations. Results: TSS can be used for sampling migrant populations for whom it is difficult to construct a sampling frame of individual members. Few studies have used TSS with migrant populations. The decision to use TSS with migrant populations depends on population characteristics and on project goals and resources because these features influence the ability of TSS to produce valid and generalizable study results. Conclusion: Proper planning, monitoring, and evaluation of TSS procedures, analysis of sampling-related variables, and attention to specific considerations (e.g., logistical, regulatory, legal, and ethical) can enhance TSS selection of representative samples of migrant,immigrant, and refugee populations.