Validation of the proposed World Health Organization staging system for HIV disease and infection in a cohort of intravenous drug users

Objective: To assess the prognostic utility of the clinical criteria of the World Health Organization's (WHO) proposed staging system for HIV disease and infection in a cohort of intravenous drug users (IVDU) from the ALIVE study. Methods: All study subjects known to be HIV-seropositive were included in this analysis. Subjects were classified as WHO clinical stage 1, 2, or 3 at their initial seropositive evaluation. Product-limit estimates and Cox proportional hazard models were used to compare time of progression to AIDS (stage 4) for the first three clinical stages. Results: Of the original cohort of 2921 IVDU in the ALIVE study, 694 were known to be HIV-positive by January 1992. At the time of their index visit, 49% of the cohort were WHO clinical stage 1, 10% stage 2 and 41% were stage 3. Demographic characteristics of the three groups were similar. Product-limit estimates for progression to AIDS over a 3-year period were 6.5% (SE, 1.5%), 10.4% (SE, 4.1%) and 17.1% (SE, 2.5%) for clinical stages 1, 2, and 3, respectively (log-rank P=0.003). In a proportional hazards model adjusting for race, age, sex and injection status within 6 months prior to enrollment, the hazard for progression to AIDS was 1.51 [95% confidence interval (CI), 0.60-3.77] and 2.39 (95% CI, 1.40-4.08) for stages 2 and 3, respectively, relative to stage 1. Conclusion: This study, in a population of IVDU, supports the utility of the WHO staging system in predicting progression from HIV seropositivity to AIDS on the basis of clinical signs and symptoms.