The AIDS epidemic in India: a new method for estimating current human immunodeficiency virus (HIV) incidence rates

Abstract

Human immunodeficiency virus (HIV) incidence rates in India were estimated using a new method that accounts for follow-up bias. Follow-up bias arises in epidemiologic cohort studies when the incidence rate among individuals who do and do not return for follow-up are different. The new method combines data on the prevalence of p24 antigenemia among all those initially screened together with the longitudinal follow-up data on the subset of patients who returned for follow-up. Using these methods, the current HIV incidence rate among patients attending sexually transmitted disease clinics in Pune, India, was 18.6% per year. It was found that follow-up bias can cause significant underestimation in HIV incidence rates, perhaps by as much as 60%. These incidence estimates, together with other HIV seroprevalence studies, suggest the HIV epidemic in India is growing rapidly.

PIP: Follow-up bias develops in epidemiologic cohort studies when the incidence rate among individuals who do and do not return for follow-up differ. The authors estimated the rates of HIV incidence in India using a new method which accounts for follow-up bias. This new method combines data on the prevalence of p24 antigenemia among all individuals initially screened together with the longitudinal follow-up data on the subset of patients who return for follow-up. The current annual rate of HIV incidence among patients attending sexually transmitted disease clinics in Pune, India, was found to be 18.6%. The study found that follow-up bias can lead to significant underestimation in HIV incidence rates, perhaps by as much as 60%. These incidence estimates, together with findings from other HIV seroprevalence studies, suggest that the HIV epidemic in India is growing rapidly.