Diagnosis of Pneumocystis carinii pneumonia in a population of HIV-positive drug users, with particular reference to sputum induction and fluorescent antibody techniques.

Between June 1990 and May 1991, 200 sputum inductions were examined by a fluorescent antibody test (FAT) for Pneumocystis carinii (PC). A total of 164 specimens were negative, 36 were positive and a further 20 inductions were unsuccessful. All patients with a positive result, seven of whom had normal chest X-rays and blood gas analyses, were treated for Pneumocystis carinii pneumonia (PCP) with symptomatic response. Two additional patients were diagnosed as PCP during the study period. No patient with a negative or unsuccessful result developed clinical PCP during that admission, although six did develop 10 episodes of PCP (FAT positive for PC on induced sputum samples) within 3 months of a negative result. Sputum induction was well tolerated by patients and not associated with adverse events. Sensitivity of FAT for PC was 95% and specificity was 100%. These results may in part be because most of the patients were injection drug users (IDUs) who often suffer from chronic productive cough, and also because sputum induction in all cases was supervised by an experienced physiotherapist.