Detection of cryptococcal antigen in bronchoalveolar lavage fluid: a prospective study of diagnostic utility

Cryptococcal pneumonia is associated with significant morbidity and mortality in immunocompromised patients. We examined the utility of screening bronchoalveolar lavage (BAL) fluid for cryptococcal antigen. In a pilot study, we found that cryptococcal antigen was always positive in unprocessed BAL specimens of seven patients with cryptococcal pneumonia and negative in 44 patients with other granulomatous diseases who acted as the control subjects. A prospective study was done of 220 immunocompromised patients (188 with human immunodeficiency virus infection, 32 with other causes of immunosuppression) undergoing BAL for fever and pulmonary symptoms. The eventual diagnosis of cryptococcal pneumonia was made in eight patients. All eight patients had a cryptococcal antigen titer greater than or equal to 1:8. There were four patients without cryptococcal pneumonia who had cryptococcal antigen titers of 1:8, there were none with higher titers. For a titer of cryptococcal antigen titer of greater than or equal to 1:8, there was 100% sensitivity, 98% specificity, a positive predictive value of 67%, and a negative predictive value of 100%. The measurement of cryptococcal antigen in the BAL can be a rapid, simple way to make a diagnosis of cryptococcal pneumonia in immunosuppressed patients with pneumonia.