Efficacy of three sputum specimens for the diagnosis of Mycobacterium avium complex pulmonary disease

Abstract

Background In Mycobacterium avium complex pulmonary disease (MAC-PD), diagnosis requires a positive culture from at least two separate expectorated sputum specimens. The optimal number of sputum examinations remains unclear. Objective This study sought to elucidate the diagnostic yield of acid-fast bacilli in MAC-PD using 3 sputum specimens and to clarify the clinical characteristics of patients with MAC-PD diagnosed using 3 sputum specimens. Furthermore, we investigated the correlation between increased number of sputum specimens and diagnostic yield. Methods We reviewed the medical records of 139 patients with MAC-PD diagnosed at Toho University Omori Medical Center for whom at least three sputum specimens were examined before treatment from November 2014 through June 2021. Patients were classified into the 3-sputum diagnosed and the non-3 sputum diagnosed groups based on diagnostic procedure; clinical and radiological characteristics were compared. We also assessed diagnostic yield with the increased number of sputum specimens. Results Diagnostic yield with 3 sputum specimens was 16.5% (23/139). The 3-sputum diagnosed group had a lower body mass index [18.6(17–19.5) vs. 19.5(18–21.5); p = 0.014], and higher chest CT score [9(6.5–13) vs. 6(4–9); p = 0.011] including cavitary lesions (39.1% vs. 19%; p = 0.037) compared with the non-3 sputum diagnosed group. When the number of sputum specimens was increased to 6, the diagnostic yield increased to 23.7% (33/139). Conclusion Diagnostic yield with 3 sputum specimens was 16.5%. Patients diagnosed using 3 sputum specimens had more severe chest CT findings including cavitary lesions. Increasing the number of sputum specimens to 6 improved diagnostic yield by 7.2%.

Diagnostic Usefulness of Liquid Culture Medium for Mycobacterium avium-intracellulare Complex Lung Disease: A Single-Centre, Retrospective Study

“…Urabe et al reported the usefulness of three sputum specimens in 139 patients with the diagnosis of MAC-LD [ 14 ]. They used OC only and reported that only 16.5% (23/139 patients) of patients were diagnosed by three sputum examinations and 81.3% (113/139) required bronchoscopy.…”

Is It Time to Say Goodbye to Sputum?

“…As per the latest American Thoracic Society (ATS)/ European Respiratory Society (ERS)/ European Society of Clinical Microbiology and Infectious Diseases (ESCMID)/ Infectious Diseases Society of America (IDSA) clinical practice guideline on the treatment of nontuberculous mycobacterial pulmonary disease ( 4 ), the diagnosis of MAC pulmonary disease requires at least two positive sputum cultures (or one positive sample from a lavage or biopsy). Even for the most prolific sputum producer, this process may take several weeks, but many people struggle to produce samples at all ( 5 , 6 ). For these patients, it is normally recommended that they proceed to bronchoscopy (or biopsy), but this can be an unpleasant and invasive procedure, and not all patients are suitable.…”