Lung Function Decline According to Clinical Course in Nontuberculous Mycobacterial Lung Disease

Background There are few data regarding the impact of nontuberculous mycobacterial lung disease (NTM-LD) on lung function during the clinical course of disease. This study aimed to assess the impact of NTM-LD on lung function decline. Methods Treatment outcomes and spirometry data at diagnosis and at least three years later were obtained from 358 patients who were diagnosed with NTM-LD between January 1999 and November 2011 using the prospective NTM registry cohort. For analysis, patients were divided into three groups: those observed without treatment, those who had treatment success, and those in whom treatment failed. Results The treatment-failure group (n = 68) had a significantly more rapid decline in FEV₁ and FVC compared with the observation (n = 118) and treatment-success (n = 172) groups (–52.2, –30.8, and –28.2 mL/y, respectively; P = .023 for FEV₁ decline; –50.4, –28.8, and –26.0 mL/y, respectively; P = .002 for FVC decline). After adjusting for confounding factors, patients with treatment failure had greater FEV₁ and FVC declines than did those observed without treatment (adjusted P = .026 for FEV₁ decline; adjusted P = .022 for FVC decline) or those treated successfully (adjusted P = .004 for FEV₁ decline; adjusted P = .002 for FVC decline). Patients treated successfully had declines in FEV₁ and FVC similar to those in the observation group. Conclusions The change of lung function was variable over a median 5-year follow-up period. Treatment failure was associated with a substantial decline in lung function in NTM-LD.