In many countries access to some populations most at risk of contracting
HIV is limited. Thus conventional sampling methods cannot be utilized for studying
various aspects of the epidemic among those populations. Respondent-Driven
Sampling (RDS) and Time-Location Sampling (TLS) methods are developed during
the recent years to allow having more accurate and more generalizable estimates on the
characteristics of the participants. RDS uses the links in the social network of
participants for recruitment of new ones and TLS uses the places where the potential
participants usually gather. Both methods have assumptions and limitations which
should be considered when applying them to different groups and situations. Prior
formative research may provide invaluable information on some factors which may
influence the researchers’ choice for using these methods including cost, time,
feasibility and coverage of target population. This may also help in guiding
development of public health interventions to mitigate the risks. Some statistical
software is available for analysing data gathered from samples together with some
modifications and tricks to decrease bias.
Keywords: Bias, Epidemic, HIV, Location, Population, Respondent, Risk,
Sampling, Selection, Snowball.