Predictive risk factors of treatment-refractory Mycobacterium avium complex lung disease

<bold>Background:</bold> <italic>Mycobacterium avium</italic> complex (MAC) lung disease is a chronic, progressive, and potentially life-threatening infection. Some cases with MAC lung disease are refractory to standard guideline-based therapy (GBT), and sputum cultures are persistently positive for acid-fast bacilli. Although early identification of treatment-refractory MAC lung disease is crucial, its predictive factors have not been fully explored. <bold>Objective:</bold> The aim of this study was to identify predictive risk factors for treatment-refractory MAC lung disease. <bold>Methods:</bold> We retrospectively reviewed 296 consecutive patients with MAC lung disease who were diagnosed between 2006 to 2020 at our institution, and enrolled 160 patients received initial GBT. Treatment-refractory MAC lung disease was defined as cases with culture positivity after at least 6 months of initial GBT, and we assessed these incidence and predictive factors. <bold>Results:</bold> Of the 160 patients, median age was 67 years old, female were 74%, and mean body mass index (BMI) was 19.4 ± 2.4 kg/m². Nodular/bronchiectatic and fibrocavitary types on computed tomography were 82% and 15%, respectively, and no macrolide-resistant MAC was observed. Twenty-four patients (15%) were treatment-refractory MAC lung disease, and they had significantly lower BMI, a higher frequency of fibrocavitary type, and tended to have lower survival rate than without treatment-refractory. Multivariate logistic regression analysis adjusted for age and sex revealed that low BMI was an independent risk factor for predicting treatment-refractory MAC lung disease (Odds ratio 0.646, p = 0.009). <bold>Conclusions:</bold> Low BMI is a predictive factor for treatment-refractory MAC lung disease.