Frequency of pulmonary tuberculosis in patients undergoing sputum induction for diagnosis of suspected Pneumocystis carinii pneumonia.

Abstract

To determine the frequency of pulmonary tuberculosis (TB) in patients with suspected Pneumocystis carinii pneumonia (PCP). Prospective study of sputum specimens from subjects undergoing diagnostic sputum induction for PCP and medical chart review. University hospital in the Bronx, New York City. A total of 373 consecutive adults with induced sputum specimens adequate for acid-fast smear and mycobacterial culture. Direct immunofluorescence for PCP, acid-fast stain, and mycobacterial culture of all induced sputum specimens. Determination of demographic characteristics, HIV risk factors, and HIV serological status. Clinical and radiographic findings of patients with TB. Proven symptomatic HIV infection was present in 251 of the 373 (67%) patients prior to sputum induction. PCP was detected in 136 out of 519 (26%) specimens, Mycobacterium tuberculosis in 10 (1.9%) specimens from nine patients. Smear was positive for acid-fast bacilli in nine (1.7%), of which seven (78%) grew M. tuberculosis and two (22%) M. avium complex. Pulmonary TB was found in nine of the 373 (2.4%) patients [95% confidence intervals (CI), 1.1-4.6]. Smears were positive for acid-fast bacilli in seven out of 10 (70%) specimens with M. tuberculosis compared with two out of 65 (3%) with other mycobacteria (P < 0.0001). Of 66 specimens that grew mycobacteria despite negative acid-fast smears, three (4.5%) were M. tuberculosis (95% CI, 0-13.3). Of the nine patients with TB, six had prior known TB, chest radiographs atypical for PCP, or both; two others had positive acid-fast smears. Only a single patient (0.27%; 95% CI, 0-0.79) had pulmonary TB, which remained unsuspected after acid-fast smear of induced sputum. Pulmonary TB occasionally occurs in patients with suspected PCP and in most cases is suggested by medical history, clinical findings, or acid-fast stain of induced sputum.