Objective: To characterize the progression to HIV-1 disease among injecting drug users (IDU) according to laboratory markers.
Design: Prospective study of cohort of HIV-1-seroprevalent IDU, with case-comparison component.
Methods: Different laboratory markers were examined as predictors of progression to HIV-1-associated diseases including AIDS in a cohort of 318 HIV-1-infected IDU. The cohort was enrolled from a methadone treatment program in the Bronx, New York, USA. The independent utility of non-CD4 cell markers was evaluated after adjustment for the association of low CD4 lymphocyte count with AIDS risk. Clinical events in the natural history of HIV-1 were related to changes in levels of two variables related to duration of infection, CD4 lymphocyte count and serum beta 2-microglobulin (beta 2M) concentration.
Results: On univariate analysis, AIDS incidence measured from baseline increased with declining CD4 lymphocyte number and percentage, increasing serum beta 2M level, low platelet count, low leukocyte count and p24 antigenemia. Among HIV-1-related outcomes prior to any AIDS diagnosis, the relative risk of pyogenic bacterial infections conferred by these markers was similar to the relative risk of AIDS. For all HIV-1 outcomes, the elevated risk encountered at CD4 lymphocyte number < or = 200 x 10(6)/l was entirely due to the high risk at < or = 150 x 10(6)/l. On multivariate analysis, control for CD4 lymphocyte count eliminated the association of any other marker with increased AIDS hazard. HIV-1-related outcomes tended to occur in this order: multiple constitutional symptoms, oral candidiasis, pyogenic bacterial infections and AIDS.
Conclusions: In HIV-1-infected IDU, several laboratory markers may predict AIDS when analyzed individually. These are not, however, independently related to increased AIDS risk after adjustment for low CD4 lymphocyte count. A CD4 count < or = 150 x 10(6)/l is more strongly related to immediate risk of adverse outcome than a count of 200 x 10(6)/l. A progressive series of clinical events is associated with markers of duration of HIV-1 infection, prior to and including AIDS diagnosis.