The AIDS incubation period in the UK estimated from a national register of HIV seroconverters

Abstract

Objectives: To monitor changes in the distribution of time intervals from HIV seroconversion to the onset of AIDS and to death and to describe factors associated with the length of these intervals, through a national register of persons with estimated dates of HIV seroconversion.Design and methods: Clinicians caring for HIV-positive individuals and laboratories performing HIV testing throughout the UK were asked to identify all persons aged 16 years or over with a history of a negative HIV antibody test within 3 years of their first positive test, including those who had died, transferred to other centres or who had become lost to follow-up. Baseline and follow-up information collected annually includes: sex, ethnic group, likely route for HIV transmission, latest CD4 count, details of antiretroviral therapy and prophylaxis for opportunistic infections, AIDS-defining events and vital status.Results: The analysis in this report was censored at 31 December 1994 and includes 961 individuals with verified previous negative antibody tests. Within 10 years of seroconversion, we estimate the probability of progressing to AIDS to be 60.2% [95% confidence intervals (Cl), 52.1-68.3] and of death from any cause to be 48.1% (95% Cl, 40.1-56.1%). Older age at seroconversion was found to be associated with faster progression to AIDS (P = 0.008) as well as shorter survival (P = 0.001). No evidence of a change in the incubation period nor of a survival benefit was observed by calendar time from 1983 to 1994.Conclusions: Preliminary results from the UK Register confirm the strong influence of age on disease progression in line with findings from a number of studies. The Register has succeeded in accruing information on a large number of seroconverters, and will continue to monitor the clinical course of HIV disease, including persons infected in the 1990s. This is important as a number of clinical trials have recently reported an improvement in survival for persons on multiple drug regimens, the long-term impact of which can only be monitored through observational studies. (C) 1998 Lippincott-Raven Publishers.