Prognostic indicators for AIDS and infectious disease death in HIV- infected injection drug users: Plasma viral load and CD4⁺ cell count

Context. Plasma human immunodeficiency virus type 1 (HIV-1) viral load and CD4⁺ cell count are used to predict prognosis of persons infected with HIV. However, whether combining these markers improves prognostic accuracy and whether they predict prognosis for injection drug users (IDUs) and nonwhite persons infected with HIV has not been extensively investigated. Objective. To evaluate plasma viral load and CD4⁺ cell count as prognostic indicators for the acquired immunodeficiency syndrome (AIDS) and infectious disease deaths. Design. Cohort study initiated in 1988 and 1989 with follow- up for up to 7.9 years. Participants. Injection drug users infected with HIV recruited from the community in Baltimore, Md. Main Outcome Measures. Plasma HIV-1 RNA and CD4⁺ cell count measured at baseline compared with time to first clinical AIDS diagnosis and death due to an Infectious disease. Results. Of 522 subjects, 96% were African American, 80% were male, 96% injected drugs within the past 6 months, and the median age was 33 years. A total of 146 cases of AIDS and 119 infectious disease deaths were seen during a median follow-up period of 6.4 years. Time-fixed baseline levels of viral load and CD4⁺ cell count were independent predictors of progression to AIDS and infectious disease deaths, but in proportional hazards models, viral load had better predictive value than CD4⁺ cell count. Kaplan-Meier analysis of time to AIDS and to infectious disease deaths by viral load (<500, 500-9999, 10 000-29 999, ≤30 000 copies/mL) at 3 levels of CD4⁺ call count (<0.20, 0.20-0.49, and ≤0.50 x 10⁹/L [<200, 200-499, and ≤500/μL]) was reduced to a 5-stage classification scheme using a backward stepwise regression procedure. The 5-year cumulative probabilities for AIDS and infectious disease deaths ranged from 0% and 0%, respectively, for group I (viral load, <500 copies/mL; CD4⁺ cell count, 0.50x 10⁹/L) to 81.2% and 76.1% respectively, for group V (viral load, ≤10 000 copies/mL; CD4⁺ cell count, 0.20x10⁹/L). Conclusions. In this study, plasma HIV-1 viral load independently and in combination with CD4⁺ cell count measurements provided powerful prognostic information for progression to AIDS and death caused by infectious disease in a population of predominantly African American IDUs. Combining categories of both markers provided a simple method for prognostically staging HIV disease.