Reconciling Survey and Surveillance-based Estimates

17-18 February 2003
Technical Consultation
Organized by Tropical Diseases Research Centre (Ndola, Zambia), UNAIDS and WHO
Lusaka, Zambia



The estimation of the number of people infected with HIV in countries, regions and globally is an important process for purposes of advocacy, programme planning and evaluation. National estimates of prevalence in countries with generalized epidemics are based on data generated by surveillance systems that focus on pregnant women who attend a selected number of sentinel antenatal clinics. UNAIDS/WHO, in close consultation with the countries, use a six-step method to obtain estimates of HIV prevalence for men and women, and an increasing number of countries have adopted these methods to develop national estimates. The major assumption is that prevalence among pregnant women is a good approximation of prevalence among the adult population (age 15-49), based on direct comparisons of adult population and antenatal clinic HIV prevalence in the same communities.

Recently, several countries have conducted national population-based surveys that include HIV testing and more countries are planning to do so in the near future. Technological developments, such as the use of blood-spotted filter paper or oral mucosal transudate for sample collection, have facilitated the collection of biological data in household surveys. Concerns about the accuracy of national estimates of adult female and male HIV prevalence based on data generated by antenatal clinic based surveillance systems have stimulated the public health demand for more representative data on HIV prevalence for the whole population. This consultation will review results and estimates of adult prevalence of HIV from three recent national surveys and compare the finding to those based on sentinel surveillance systems.


  • To share the methods, results and issues related to recent population-based surveys with HIV data collection, including sampling methods and laboratory procedures
  • To present comparisons of HIV prevalence estimates from national surveys and from antenatal clinic based surveillance, in defined geographical entities (e.g. in rural versus urban areas, in provinces, in specific antenatal clinics and their catchment areas)
  • To present results from further analysis with regard to non-response
  • To discuss how surveys can be used to improve national surveillance system based estimates of HIV prevalence


UNAIDS/WHO Estimates: how are they made?

Comparison of prevalence among ANC clinic attenders and the general population in selected small-area population-based studies

Mali: issues arising from the national population-based survey

South Africa: issues arising from the comparison of national DHS and data from the surveillance results

Zimbabwe: issues arising from the comparison of national DHS and data from the surveillance results

Working groups (illustrative questions):

  • How to deal with non-response issues?
  • What laboratory procedures are most suitable for surveys and surveillance?
  • Can survey data be used to adjust ANC clinic based estimates?
  • How can surveys best be integrated in surveillance systems?
  • How can the design of national surveys be improved to provide better surveillance data?