Analysis of induced sputum in the diagnosis of Pneumocystis carinii pneumonia

Sixty-two patients with possible AIDS-associated Pneumocystis carinii pneumonia (PCP) were studied to determine the diagnostic usefulness of sputum analysis and whether or not the results of sputum analysis are related to severity of disease. Induced sputum was stained with Gomori Methenamine silver and modified Wright Giemsa stains. Indicators of disease severity were: extent of chest roentgenographic infiltrate, serum lactic dehydrogenase activity, alveolar-arterial oxygen tension difference, and total blood lymphocyte count. All patients with sputum negative for Pneumocystis underwent bronchoscopy with bronchoalveolar lavage. Sputum analysis was 71% sensitive and 100% specific for the diagnosis of PCP. The negative predictive value of sputum analysis was 48%. There was no relationship between sputum results and the severity of PCP. This study led to the conclusions that sputum analysis is a sensitive, specific, rapid, and low-cost technique for the diagnosis of PCP, and that the sensitivity of sputum analysis for the detection of PCP is not affected by the severity of PCP.