Academic journal article Bulletin of the World Health Organization

HIV Testing in National Population-Based Surveys: Experience from the Demographic and Health Surveys/Depistage Du VIH Dans le Cadre Des Enquetes Nationales En Population : Experience Fournie Par Les Enquetes Demographiques et De sante/Pruebas De Deteccion del VIH En Encuestas Nacionales De Base Poblacional: Experiencia De Las Encuestas Sobre Demografia Y Salud

Academic journal article Bulletin of the World Health Organization

HIV Testing in National Population-Based Surveys: Experience from the Demographic and Health Surveys/Depistage Du VIH Dans le Cadre Des Enquetes Nationales En Population : Experience Fournie Par Les Enquetes Demographiques et De sante/Pruebas De Deteccion del VIH En Encuestas Nacionales De Base Poblacional: Experiencia De Las Encuestas Sobre Demografia Y Salud

Article excerpt

Introduction

Reliable data on the spread of human immunodeficiency virus (HIV) and its risk factors in the general population are essential for an effective response to the epidemic and its consequences. In countries with generalized epidemics, national estimates of HIV prevalence and trends in the adult population are generally derived indirectly from HIV surveillance among pregnant women attending selected antenatal clinics. (1-4)

Facilitated by biomedical progress, such as the use of dried blood spot (DBS) samples on filter paper for HIV testing, the collection and testing of blood samples has become feasible in large-scale national surveys. In recent years, the Demographic and Health Surveys (DHS) programme has become a major source of data on HIV prevalence in many countries. Since 2001, 12 countries have completed a DHS or similar survey that has included HIV testing and more than a dozen are in various stages of implementation. The DHS are primarily health interviews with questions on maternal and child health, family planning, nutrition and related issues, but increasingly they include collection of other biological and clinical data such as anthropometric measurements and testing for anaemia. The surveys also include an acquired immunodeficiency syndrome (AIDS) module. In some countries, the survey has exclusively focused on the collection of information on HIV/AIDS (AIDS Indicator Survey).

This article describes the methods used in DHS to collect nationally representative data on HIV prevalence. Results from the first eight national surveys during 2001-04 are presented and evaluated for bias due to non-response. The potential role of national population-based surveys in national systems for HIV surveillance is discussed.

Methods

General survey methodology

The DHS programme has conducted more than 200 national household surveys in more than 70 developing countries worldwide since 1984. The challenges in designing and implementing DHS in developing countries, as well as the lessons learned from more than 20 years of experience, are discussed elsewhere. (5) It is well recognized that all aspects of survey planning and implementation, such as sample design, developing and field-testing survey instruments, training of survey personnel, and careful supervision of data collection and processing, are critical in collecting high-quality data in such surveys. (6)

Of particular importance for the interpretation of the results on HIV prevalence from the surveys is the sampling methodology. The DHS selects random sample clusters from a national sampling frame, usually from the national population census. Within the selected clusters, a full listing of all households is made before the survey and a systematic random sample of households is taken. During the main fieldwork, eligible women and men, usually aged 15-49 and 15-59 years, respectively, are selected for HIV testing. An individual is only considered absent after three callback visits.

To obtain reliable national estimates of HIV prevalence disaggregated by sex and urban versus rural residence, a representative sample of at least 3000 households is required. If, on average, there is one eligible male and one eligible female in each sample household and if 10% of those eligible do not participate in the survey, this yields a final sample of approximately 5400 tested adults. For a population with an estimated HIV prevalence of 5%, such a sample would provide a 95% confidence interval of 4.3-5.7% at the national level. Larger sample sizes are required if the prevalence of HIV is lower or if further disaggregation of HIV estimates is desired.

Specimen collection

In most surveys, HIV testing is done using DBS samples of capillary blood from a finger prick, collected on special filter paper. The only exceptions are the 2002 Dominican Republic DHS, which used oral mucosal transudate, and the 2001-02 Zambia DHS and the 2004-05 Uganda HIV/AIDS Sero-Behavioural Survey where venous blood was used (data from Uganda not yet available). …

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