Rapid diagnosis of cryptococcal meningitis by microscopic examination of centrifuged cerebrospinal fluid sediment.

Abstract

The classic India ink test is positive in only half of cryptococcal meningitis cases, and reliable, rapid cryptococcal antigen (CRAG) testing requires technical expertise and facilities not always available. We therefore examined cerebrospinal fluid (CSF) sediment using May-Giemsa, periodic acid-Schiff, and Gram stains in 16 patients with cryptococcal meningitis. The India ink test was positive in seven patients (44%), while microscopic examination of sediment revealed cryptococci in 13 (81%); in six of these 13 the India ink test was negative. Both methods failed to detect the pathogen in the remaining three patients. CRAG testing in CSF was negative in two patients (one with acquired immunodeficiency syndrome, one with diabetes mellitus) whose India ink test also was negative while cryptococci were identified in their CSF sediment. No false positives occurred with CSF May-Giemsa staining in 27 cases of aseptic meningitis with negative cultures for Cryptococcus. In all, microscopic examination of centrifuged and stained CSF sediment proved more sensitive for rapid diagnosis of cryptococcal meningitis than the India ink method, and in two of our patients cryptococci were seen in centrifuged CSF sediment despite negative CRAG and India ink tests.