Analysis of disease progression from clinical observations of US Air Force active duty members infected with the human immunodeficiency virus: distribution of AIDS survival time from interval-censored observations

Abstract

A non-parametric estimator of the AIDS survival time (after developing AIDS) is computed for the AIDS data set from the US Air Force (USAF). Survival times are unobservable. They are censored by the screening mechanism. The Armstrong Laboratory's Epidemiologic Research Division maintains data on over 954 active duty US Air Force (USAF) individuals who tested positive for human immunodeficiency virus (HIV) antibodies. Many have been clinically evaluated seven times since 1986. The HIV-positive individual is classified in seven stages of the disease complex as time progresses. Exact times of transition from one stage to the next are unknown. It is known that transition occurred between two consecutive evaluations. The aim of this study is to analyse distributions of the times that individuals spend in each stage of the HIV disease complex. We will discuss methods used to obtain non-parametric estimators of the distribution of times that individuals spend in stage 6. Finally, it is hoped to model the median time spent in each stage of the disease. This, along with incidence and separation data, will allow the prediction of the impact of HIV disease on USAF individuals and medical care systems.