A Comparison of Results from Two Sampling Approaches in the South African National HIV Prevalence, Incidence and Behavior Survey, 2012

Abstract

Background : South Africa implements variations of second generation suveilance surveys to monitor human immunodeficiency virus (HIV) epidemic. Objective : This paper compares HIV estimates from two design variations: take all approach and sub-sampling approach to ascertain if any changes in HIV epidemic are due to methodological changes or inherent evolution of the epidemic. Methods : A multi-stage stratified cluster sample of 1000 census enumerator areas was implemented with 15 households systematically sampled within each census enumerator area. In each household, every member was invited to participate ( take all approach). To compare to the previous survey designs, a sub-sampling approach of at most four people from each household was implemented by randomly sampling one person from each age group: <2 years, 2 - 14 years, 15 to 24 years and 25 years and above. Results : HIV estimates were comparable with no systematic pattern. Prevalence estimates were slightly higher 12.2% [11.4% - 13.1%] in the take all compared to 11.6% [10.6% - 12.6%] in the sub-sampling approach. Estimates from sub-sampling approach were more variable. The design effects in the take all approach were also slightly higher than those obtained in the sub-sampling. The overall synthetic measure of homogeneity for both methods was ρ = 0.10. Conclusion : In conclusion, as the household size increases the number of people living with HIV in each household increase s thus increasing intraclass correlation. Similarity of resulting HIV estimates is re-assuring. However, the take all approach is more preferable than sub-sampling approach as it allows for detailed analyses of HIV data such as estimating discordance between sexual partners and parent-child pair.