The usefulness of induced sputum in the diagnosis of Pneumocystis carinii pneumonia in patients with the acquired immunodeficiency syndrome.

Thirty-two patients with or suspected of having the acquired immunodeficiency syndrome were evaluated for opportunistic lung infection using examination of sputum induced by inhalation of 3% saline. The specimens obtained were stained with Giemsa stain and examined for Pneumocystis carinii. Smears of sputum were also appropriately stained and examined for acid-fast organisms and fungi, as well as cultured for these organisms. Patients whose sputum did not contain P. carinii had bronchoscopy within 24 h of sputum induction. Twenty-five of the 32 patients were ultimately determined to have P. carinii pneumonia. Of these, 14 were detected by examination of sputum (sensitivity, 56%). Of 18 patients whose sputum did not contain P. carinii, 11 had the organism detected in specimens obtained by bronchoscopy (negative predictive value, 39%). There were no clinical features that identified patients more likely to have a positive sputum examination. No additional treatable lung pathogens appeared to be missed by sputum examination. In this select population, examination of induced sputum establishes the diagnosis of P. carinii pneumonia in a significant proportion of patients, thereby decreasing the need for more invasive procedures.