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Diagnostic Yield of Sputum, Induced Sputum, and Bronchoscopy after Radiologic Tuberculosis Screening

Pneumology, Kantonsspital St. Gallen, St. Gallen; Hospital Saint Loup, Pompaples; University Hospital Basel, Basel; Swiss Federal Office of Public Health; Swiss Lung Association, Bern; Tuberculosis Consultant Services, Kirchlindach; and Kantonsspital Münsterlingen, Münsterlingen, Switzerland

Correspondence and requests for reprints should be addressed to Otto D. Schoch, M.D., F.C.C.P., Pneumology, Kantonsspital St. Gallen, CH-9007 St. Gallen, Switzerland. E-mail: otto.schoch{at}kssg.ch

Rationale: To assess feasibility and yield of diagnostic procedures after active case finding for tuberculosis with radiologic screening at the three main entry points for asylum seekers to Switzerland.

Method: Prospective multicenter study on the value of symptoms, spontaneous and induced sputum, and bronchoscopy for the confirmation of tuberculosis in radiologically selected cases.

Results: Among 101 asylum seekers examined, spontaneous sputum was collected "on the spot" in 83 and yielded 7 (54%) of 13 smear-positive and 13 (39%) of 33 culture-positive cases. Morning sputum, collected in 84, yielded 8 (62%) and 16 (49%), and the two spontaneous sputa combined 9 (69%) and 20 (61%), respectively. Two additional induced sputa, collected in 91 persons, yielded no additional smear-positive, but yielded seven culture-positive cases (yield, 82%). Bronchoscopy, performed in 87 of 92 sputum smear–negative cases, yielded four additional smear-positive and six culture-positive cases. Culture confirmation was independently and significantly predicted by obtaining a specimen using bronchoscopy (adjusted odds ratio, 11.0; 95% confidence interval, 1.9–62) and a prior decision to treat (adjusted odds ratio, 3.0; confidence interval, 1.1–8.1).

Conclusion: Radiographic anomalies compatible with tuberculosis found during screening are a poor guide to initiation of treatment. Respiratory and systemic symptoms correlated weakly with culture confirmation of tuberculosis. All radiologically selected cases must be examined with on-the-spot and early-morning sputum, regardless of symptoms. If both specimens are smear negative, the yield is increased by bronchoscopy and, to a lesser extent, by two samples of induced sputum. The examination of any single specimen has a low yield of 36 to 63% and is insufficient to exclude active tuberculosis.

Key Words: tuberculosis, pulmonary • immigrants • mass chest X-ray

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject The examination of respiratory specimens to confirm suspected TB is standard of care. However, after radiologic TB case finding, the yields of on-the-spot spontaneous and induced sputum, morning sputum, and bronchoscopy have not been determined. What This Study Adds to the Field Radiographic abnormalities consistent with tuberculosis and found during screening are a poor indicator of the need for treatment. The addition of sputum testing and bronchoscopy improve diagnostic yield for tuberculosis.

 

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