The effect of the 1993 European revision of the AIDS case definition in Italy: Implications for modelling the HIV epidemic

Objectives: To evaluate the effect of the 1993 European AIDS definition on reducing pre-AIDS mortality and to what degree an earlier diagnosis can be made. Design: Prospective observational study. Methods: All patients diagnosed between January 1993 and December 1994 and reported to the National AIDS Registry from four Italian regions, who met only the new criteria for the 1993 case definition (AIDS-1993) were studied. Follow-up of patients who did not eventually meet the 1987 definition (AIDS-1987), or had not died from other causes (pre-AIDS-1987 death), was censored at the last available clinical visit before 1 April 1996. We analysed the data using Kaplan-Meier nonparametric survival analysis and Cox proportional hazards model. Results: A total of 74 (4.1%) individuals met only the new criteria. Of these, 49 (62.2%) were men, 42 (56.8%) had pulmonary tuberculosis, 22 (29.7%) had recurrent bacterial pneumonia, and 10 (13.5%) had cervical cancer. During followup, 35 (45.3%) individuals developed an AIDS-1987 disease, and 10 (13.5%) died without fulfilling the AIDS-1987 definition. Pre-AIDS-1987 death accounted for 22.2% (10 out of 45) of the subsequent outcomes observed prior to 1 April 1996. Using Kaplan-Meier technique, we estimated that after 9.8 months 50% of these individuals were diagnosed with AIDS-1987 disease, or died without such a diagnosis. Individuals with lower CD4+ count at the time of the AIDS-1993 diagnosis progressed more rapidly to AIDS-1987 than those with a higher count. In contrast, pre-AIDS-1987 mortality was strongly associated with injecting drug use, whereas no association was found with CD4+ count. Conclusions: Approximately 50% of individuals with one of the three new AIDS-defining diseases will develop an AIDS-1987 disease or will die within 1 year. Time from AIDS-1993 to AIDS-1987 disease is strongly associated with CD4+ count at diagnosis. AIDS-1993 diagnosis reduced the pre-AIDS-1987 mortality in injecting drug users. Furthermore, approximately 20% of individuals diagnosed with AIDS-1993 disease are expected to die without developing an AIDS-1987 disease. These data should be useful for correcting the AIDS incidence curve in Europe for the effect of the changes in the AIDS definition.