Sputum induction versus gastric washing for the diagnosis of pulmonary mycobacterial disease

To the Editors: The diagnosis of pulmonary mycobacterial disease is based primarily on the isolation of mycobacteria in sputum specimens. The collection of at least three samples of spontaneously expectorated sputum on three different days is the standard diagnostic procedure for patients with suspected pulmonary tuberculosis and non-tuberculous mycobacterial lung disease 1, 2. For patients who are unable to expectorate, bronchial secretions, aspirated by fiberoptic bronchoscopy, or gastric washings (GWs) are collected 1, 3. These procedures require the patient to be hospitalised, are fastidious and unpleasant for the patient, and the yield of GWs for the diagnosis of pulmonary tuberculosis is considered to be rather low 3. Another option is sputum induction (SI) with nebulised hypertonic saline 4, 5. SI does not necessitate the patient to be hospitalised. However, it is a complicated procedure that requires trained staff and respiratory isolation conditions 4. The diagnostic value of this procedure is still debated: several studies have reported that sputum induction has a rather low diagnostic yield 6; other studies have found that SI compares favourably with GW and bronchoalveolar lavage in patients with suspected pulmonary tuberculosis 4. We therefore decided to conduct a prospective study to compare the diagnostic value of SI with that of GW in adult patients with suspected pulmonary mycobacterial disease. The study population was comprised of consecutive patients admitted to the Dept of Pulmonary Diseases of Ambroise Pare University Hospital (Boulogne, France) between January 2003 and March 2009 because of a clinical suspicion of pulmonary mycobacterial disease. The study was approved by the Ethics Committee for the Protection of Subjects Participating in Biomedical Research at our institution. Patients were included in the study if a spontaneously expectorated sputum sample could not be obtained or was insufficient in …