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Time location sampling: still relevant after all those years?

Time location sampling: still relevant after all those years? . Frits van Griensven, PhD, MPH Thailand MOPH – US CDC Collaboration and Division of HIV/AIDS Prevention US Centers for Disease Control and Prevention Global HIV/AIDS Surveillance Meeting, Bangkok, March 2 – 5, 2009.

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Time location sampling: still relevant after all those years?

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  1. Time location sampling: still relevant after all those years? Frits van Griensven, PhD, MPH Thailand MOPH – US CDC Collaboration and Division of HIV/AIDS Prevention US Centers for Disease Control and Prevention Global HIV/AIDS Surveillance Meeting, Bangkok, March 2 – 5, 2009

  2. Time location sampling is not that old and has always been useful

  3. The prevalence of HIV and associated risks among populations of men who have sex with men (MSM) in Thailand, 2003 - 2007

  4. Survey of HIV infection and risk behaviour among men who have sex with men, Vientiane, Lao PDR, 2007

  5. Field work

  6. Since there is no sampling frame for groups at behavioral risk for HIV infection, the generalizability and representativeness of TLS and RDS are unknownWe have no population parameters to compare our samples with

  7. TLS versus RDS TLS can be used if population is present at venues (internet may be considered a venue as well)TLS can be used when most persons at risk are not hidden and not hard to reach (MSM for instance can always find each other in large numbers) TLS may represent the population attending venuesTLS is a simple, but labor intensive, method good for tracking HIV prevalence trends among those at the highest riskTLS provides eligibility and response rates

  8. TLS versus RDS Statistical methods for TLS are well established -- cluster sampling of venue – time clustersTLS is not a convenient way of samplingTLS forces public health workers to identify, describe and map venues, and to interact sensitively with gatekeepers and members of the target population TLS is easy to integrate in sentinel surveillance systems and has a high degree of replicability

  9. TLS versus RDS RDS can be used if population is not immediately availableRDS can be used if persons at risk are hidden and hard to reachRDS may represent the population of interconnected recruits RDS is a complicated and labor intensive method for tracking HIV prevalence trends RDS may not provide reliable eligibility and response rates

  10. TLS versus RDS Statistical methods for RDS are not well established, e.g., continuing discussions about the magnitude of design-effectRDS is a convenient way of samplingRDS does not force public health workers to identify, describe and map venues, and interact sensitively with gatekeepers and members of the target population RDS is difficult to integrate in sentinel surveillance system of most developing countries and is difficult to replicate

  11. Conclusion TLS and RDS both have their strengths and weaknesses and one is not per definition better than the otherWhether one chooses TLS or RDS should depend of the specifics of the situation, e.g., population visible or not, academic institution or ministry, etc, etc

  12. Disclaimer "The findings and conclusions in this presentation are those of the author and do not necessarily represent the views of the US Centers for Disease Control and Prevention” Thank you

  13. Gay guides and maps are a valuable source for MSM venue identification

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