Studying dynamics of the HIV epidemic: population-based data compared with sentinel surveillance in Zambia.
OBJECTIVE
To establish population-based HIV survey data in selected populations, and to assess the validity of extrapolation from HIV sentinel surveillance amongst antenatal clinic attenders (ANC) to the general population.


METHODS
In a population survey, adults aged > or = 15 years were selected by stratified random cluster sampling (n = 4195). The survey was carried out in catchment populations of clinics used for national HIV surveillance. The methodology allows detailed comparisons of HIV infection patterns to be made in two areas (urban and rural). Whereas the sentinel surveillance used serum-based HIV testing, the population survey used saliva (93.5% consented to provide a saliva sample).


RESULTS
Surveillance of ANC tended to underestimate the overall HIV prevalence of the general population, but differences were not statistically significant. In the urban area, the adjusted overall HIV prevalence rate of ANC (aged 15-39 years) was 24.4% [95% confidence interval (CI), 20.9-28.0] compared with 26.0% (95% CI, 23.4-28.6) in the general population. The respective rural estimates were 12.5% (95% CI, 9.3-15.6) versus 16.4% (95% CI, 12.1-20.6). Age-specific prevalence rates showed ANC to overestimate infection in teenagers (aged 15-19 years), whereas in the reverse direction of those aged > or = 30 years. Teenagers analysed by single year of age revealed both ANC and women in the general population with about the same steep increase in prevalence by age, but the former at consistently higher rates. Extrapolations might be biased substantially due to the higher pregnancy rates amongst uninfected individuals.


CONCLUSIONS
ANC-based data might draw a rather distorted picture of current dynamics of the HIV epidemic. Even though representing an obvious oversimplification, extrapolations of overall prevalence rates may correlate with that of the general population.
Institute of Community Medicine, University of Tromsø, Norway.
K
K
Fylkesnes
Z
Z
Ndhlovu
K
K
Kasumba
R
R
Mubanga Musonda
M
M
Sichone
D015492:AIDS Serodiagnosis; D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D004196:Disease Outbreaks; D004522:Educational Status; D005260:Female; D006678:HIV; D015658:HIV Infections / Q000453:epidemiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000453:epidemiology*; D011295:Prenatal Care / Q000706:statistics & numerical data; D015995:Prevalence; D015203:Reproducibility of Results; D012424:Rural Population; D012463:Saliva / Q000821:virology; D012494:Sampling Studies; D018571:Sentinel Surveillance; D017678:Sex Distribution; D014505:Urban Population; D015024:Zambia / Q000453:epidemiology