Impact of pulmonary nontuberculous mycobacterial treatment on pulmonary function tests in patients with and without established obstructive lung disease

Abstract

There is relatively little data regarding pulmonary function test (PFT) findings and impact of treatment on PFT in pulmonary nontuberculous mycobacterial (pNTM) disease. We performed a retrospective study on pNTM patients. Clinical, radiographical, microbiological and PFT data were reviewed. Patients were divided into three groups based on pre-existing obstructive lung disease: (i) normal (no chronic obstructive pulmonary disease (COPD) or asthma); (ii) asthma; and (iii) COPD. We studied pre-treatment PFT and assessed for PFT changes after anti-mycobacterial therapy. A total of 96 patients fulfilled ATS disease criteria and had pre-treatment PFT (54 'normal', 18 asthma, 24 COPD). Most common causative NTM was Mycobacterium avium complex (76%), and radiographical disease type was nodular bronchiectasis (71%). Before therapy, all groups had PFT abnormalities, including obstruction, gas trapping and at least mildly low diffusion capacity of carbon monoxide (DLCO). Pre-treatment PFT abnormalities were more pronounced among patients with asthma and COPD. A total of 44 patients had >12 months anti-mycobacterial therapy and post-treatment PFT. There tended to be small and generally not statistically significant reductions in spirometry and DLCO in most groups. Among the nine asthmatic patients, there was a small reduction in residual volume (RV) (1.5% predicted, P = 0.01) and RV/total lung capacity (by 7% predicted, P = 0.06). Patients with pNTM have abnormal PFT, and treatment was not associated with substantial changes therein. Asthmatics may experience some improvements in gas trapping after NTM therapy, but because the sample size and the observed change were both small, this requires further investigation.