ESTIMATION OF CURRENT HUMAN-IMMUNODEFICIENCY-VIRUS INCIDENCE RATES FROM A CROSS-SECTIONAL SURVEY USING EARLY DIAGNOSTIC-TESTS

In sharp contrast to the considerable worldwide epidemiologic data ava ilable on acquired immunodeficiency syndrome incidence and human immun odeficiency virus (HIV) seroprevalence, there is relatively little inf ormation about current levels of HIV incidence rates. The authors sugg est a novel approach for estimating current HIV incidence rates based on a single cross-sectional survey and on an epidemiologic model, The approach is based on diagnostic tests for HIV p24 antigen to identify individuals in the preantibody or window period (time between exposure to HIV and appearance of detectable HIV antibodies), Individuals in t he preantibody period are likely to have been infected very recently b ecause the duration of the preantibody period is relatively short, The authors report data on the duration of p24 antigenemia prior to HIV s eroconversion. This duration together with the prevalence of p24 antig enemia obtained from a cross-sectional survey are used in an epidemiol ogic model to estimate current incidence rates, This approach of estim ating incidence rates may be especially useful in developing countries and high-risk populations in which it is difficult to follow cohorts to identify seroconverters, and in the design of vaccine efficacy stud ies in which current incidence rates are crucial for calculating sampl e sizes.