Characterization of non-tuberculous mycobacterial pulmonary disease and pulmonary tuberculosis in patients with AFB smear-positive sputum: A retrospective comparative study.

Background: Distinguishing nontuberculous mycobacteria pulmonary disease (NTM-PD) from pulmonary tuberculosis (PTB) is a challenge especially in patients with positive sputum smear of acid-fast bacilli (AFB). This study aimed to compare and identify the clinical characteristics between the two diseases among patients with positive sputum AFB.

Methods: From February 2017 through March 2021, patients with positive sputum AFB were reviewed in two hospitals of China. Among them, clinical data of NTM-PD and PTB patients was collected and compared.

Results: 76 cases of NTM-PD and 92 cases of PTB were included in our study. When compared with PTB, NTM-PD patients were older (59.2 ± 11.4 vs 44.2 ± 19.5 years, P < 0.001) and manifested more hemoptysis and dyspnea (28.9 % vs 14.1 %, P < 0.05; 48.7 % vs 17.4 %, P < 0.001 respectively). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) for Xpert were 85.9 %, 96.1 %, 96.3 %, 84.9 %, respectively, compared to 94.2 %, 81.1 %, 83.1 %, 93.5 %, respectively for T-spot in diagnosing PTB. In radiological features, NTM-PD affected more lobes (4.53 ± 0.89 vs 3.61 ± 1.41, P < 0.001) and showed more consolidation (50 % vs 32.6 %, P < 0.05), destroyed lung (22.7 % vs 9.8 %, P < 0.05), honeycomb lung (26.7 % vs 6.5 %, P < 0.001) but less nodules (80.3 % vs 95.7 %, P < 0.05), tree-in-bud sign (49.3 % vs 87 %, P < 0.001), and satellite nodules (14.5 % vs 90.2 %, P < 0.001) than PTB. Age (odds ratio [OR], 1.043; 95 % confidence interval [CI], 1.018-1.069, P < 0.05), hemoptysis (OR, 3.552; 95%CI, 1.421-8.729, P < 0.05), and dyspnea (OR, 2.631; 95%CI, 1.151-6.016, P < 0.05) were independently correlated with NTM infection.

Conclusions: NTM-PD and PTB share similar clinical manifestations. Among them, advanced age, hemoptysis, and dyspnea are the independent predictors for NTM infection. Xpert is an efficiency analysis in discriminating between NTM-PD and PTB in patients with positive sputum AFB.