Toxoplasmic encephalitis in HIV-infected persons: Risk factors and trends

Objective: To evaluate the incidence of and risk factors for toxoplasmic encephalitis among HIV-infected persons. Design: Medical facility-based prospective medical record reviews of consecutive patients. Methods: We analysed data collected from January 1990 through August 1995 in more than 90 inpatient and,outpatient medical facilities in nine US cities. Incidence was calculated as cases per 100 person-years and risk ratios (RR) for annual incidence were calculated using proportional hazards regression while controlling for city, sex, race, age, county of birth, HIV exposure mode, and prior prescription of trimethoprim-sulfamethoxazole (TMP-SMX). Results: The incidence of TE was 4.0 cases per 100 person-years among persons with a CD4+ T-lymphocyte count of < 100x10(6)/l. In multivariate analysis, among the nine cities the annual incidence of toxoplasmosis was significantly lower only in Denver [RR, 0.3; 95% confidence interval (CI), 0.1-0.7; referent city, Seattle]. Persons prescribed TMP-SMX were half as likely to develop toxoplasmic encephalitis as those who were not (RR, 0.5; 95% CI, 0.4-0.7). Of the 4173 persons with AIDS (1987 Centers for Disease Control and Prevention definition) who died during the study period, 267 (6.4%) had toxoplasmic encephalitis in the course of HIV disease. Conclusions: Toxoplasmic encephalitis in HIV-infected persons varies by geographic area in the United States. TMP-SMX reduces the risk for toxoplasmic encephalitis.