Tuberculosis and AIDS: a retrospective, longitudinal, multicentre study of Italian AIDS patients. Italian group for the study of tuberculosis and AIDS (GISTA).

We report the results of a retrospective, longitudinal, multicentre study which estimated the cumulative incidence of tuberculosis in patients who eventually develop AIDS, investigated the characteristics of AIDS patients in relation to the development of tuberculosis, and endeavoured to determine the degree of HIV-induced immunosuppression at which tuberculosis occurs. The Infectious Disease Units of 23 hospitals located in 11 of the 20 regions of Italy participated in this study. We investigated 1691 patients with AIDS diagnosed in 1988 and 1989 and reported to the National AIDS Registry by participating units before the end of December 1990. By that time M. tuberculosis had been cultured from 193 patients (11.4%). Compared with intravenous drug users (the largest HIV transmission category), only homosexual men had a statistically significant lower risk of tuberculosis (relative risk = 0.65; 95% confidence interval 0.43-0.99). The median count of CD4+ lymphocytes at the time tuberculosis was diagnosed was 82/mm3 (range 1-752); only four patients (2.1%) had CD4+ lymphocyte counts of more than 500/mm3, and 36 (18.7%) of over 200/mm3. We conclude that in Italy the proportion of AIDS patients who develop tuberculosis is higher than in other industrialised countries and differences in the incidence of tuberculosis among various HIV-transmission categories are less marked than in other western countries. Tuberculosis associated with HIV infection may occur in those with widely differing CD4+ counts, although the risk increases consistently in proportion to the degree of immunosuppression.