Laboratory markers and the risk of developing HIV-1 disease among injecting drug users.

Objective: To characterize the progression to HIV-1 disease among injection drug users (IDU) according to laboratory markers. D 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(2)M) concentration. Results: On univariate analysis, AIDS incidence measured from baseline increased with declining CD4 lymphocyte number and percentage, increasing serum beta(2)M 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 less than or equal to 200 x 10(6)/l was entirely due to the high risk at less than or equal to 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 of 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 less than or equal to 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.