Differential Survival of Patients With AIDS According to the 1987 and 1993 CDC Case Definitions

OBJECTIVE: To evaluate the impact of the 1993 Centers for Disease Control and Prevention (CDC) revised classification system for human immunodeficiency virus and expanded surveillance case definition for acquired immunodeficiency syndrome (AIDS) on the number of cases and on survival of patients with AIDS. DESIGN: Retrospective analysis of data from a prospective cohort study of patients treated with zidovudine. PATIENTS: A total of 3515 patients enrolled in the Italian National Registry of Zidovudine-Treated Patients between July 1987 and December 1991 were analyzed. MAIN OUTCOME MEASURES: Numbers and survival probability estimates (using the Kaplan-Meier method) for patients satisfying the 1993 CDC case definition compared with patients fulfilling the 1987 CDC classification. Multiple regression analysis was also used to analyze the combined effect of independent variables on survival. RESULTS: According to the new classification system, the number of AIDS cases in the study population would increase by 188%. While the median survival of patients meeting the 1987 definition was 24 months, at the end of 57 months 53% of patients meeting the 1993 definition were still alive. Among the patients meeting the laboratory criteria for AIDS diagnosis using the new definition (CD4+ lymphocyte count < 0.20 x 10(9)/L 200/microL), the presence of an AIDS-defining illness was a strong independent predictor of death. CONCLUSIONS: The application of the new definition results in a considerable increase in the number of cases. Survival for patients classified according to the 1993 definition is much longer than for those classified with the 1987 definition. Clinical status plays a major role in predicting survival outcome among patients whose CD4+ lymphocyte counts meet the new case definition.