A prospective study of criteria for the diagnosis of toxoplasmic encephalitis in 186 AIDS patients. The BIOTOXO Study Group.

ABSTRACT

OBJECTIVE: To define the factors associated with diagnosis of toxoplasmic encephalitis (TE) in AIDS patients; and to establish a rational procedure for the clinician faced with a decision concerning empiric antitoxoplasma therapy. DESIGN: A 15-month prospective multicentre cohort study in France. METHODS: One hundred and eighty-six consecutive HIV-positive inpatients undergoing empiric antitoxoplasma therapy for a first episode of presumed TE were monitored. The clinician's initial estimation of the probability of response to antitoxoplasma therapy was recorded. In addition, a validation committee classified cases as TE or non-TE. RESULTS: Among the 186 patients, the following variables were significantly more frequent in TE (n = 113) than non-TE (n = 73) patients fever (59% versus 40%). headache (55% versus 33%), seizures (22% versus 11%), suggestive lesions on the brain scan (98% versus 76%), positive Toxoplasma serology (97% versus 71%). Median CD4+ lymphocyte count was significantly higher in TE than in non-TE (27 x 10(6)/l versus 11 x 10(6)/l). The rate of TE in patients on systemic antiprotozoal prophylaxis at entry was 43% as compared with 75% in patients without previous prophylaxis. Pre-therapy estimation of response to empiric therapy was highly correlated with final diagnosis. Multivariate logistic regression analysis showed that the following variables contributed independently to the diagnosis of TE clinician's estimation of response to treatment at entry > 75%; absence of systemic antiprotozoal prophylaxis; seizures; headache; suggestive lesions on CT or MRI brain scan; and positive Toxoplasma serology. CONCLUSIONS: A linear logistic model is proposed which uses significant variables, which are readily available. This model gives good accuracy to classify suspected cases of TE.