Background: To identify non-tuberculous mycobacteria (NTM) infections in initially acid-fast bacilli (AFB) smear-positive patients more quickly and effectively, we attempted to establish a predictive model and validate it in clinical practice.Methods: A total of 125 AFB smear-positive patients with mycobacteriosis diagnosed in the Respiratory Department of Shanghai Pulmonary Hospital were retrospectively analyzed including 64 cases of NTM and 61 cases of pulmonary tuberculosis (PTB), to identify the clinical features distinguishing NTM from PTB patients. A bivariate regression was then set up to determine the independent predictive risk factors to NTM infections. A receiver operating characteristic (ROC) curve was used to determine the model's predictive discrimination. Finally, the model was veri ed both internally and externally for its predictive ability.Results: Compared with PTB, female patient, the symptom of hemoptysis, the exists of bronchiectasis, and negative test for QuantiFERON tuberculosis (QFT) were more common in NTM patients (78.1% vs.34.4%, 37.5% vs. 11.5%, 76.6% vs. 19.7%, 82.8% vs. 8.2%, respectively, P≤0.001). The lesions on chest high-resolution computed tomography (HRCT) in NTM patients were more commonly involved in the right middle lobe (87.5% vs. 52.5%, P<0.001) and left lingular lobe (71.9% vs. 50.8%, P=0.016), and cystic change was more commonly morphological alteration (32.8% vs. 8.2%, P=0.001). Binary regression analysis showed that female patient, the exists of bronchiectasis, negative test for QFT and right middle lobe lesion were independent risk factors for NTM in AFB smear-positive patients (P<0.05). A ROC curve combining the four risk factors showed a sensitivity and speci city of 85.9% and 93.4%, respectively, and the area under the curve (AUC) was 0.963. Moreover, internal validation and external validation of the later clinical data both con rmed the effectiveness of the model.
Conclusions:The predictive model would be useful for early differential diagnosis of NTM in initially AFB smear-positive patients.(AFB) smear, he/she is likely to be diagnosed with pulmonary tuberculosis (PTB) and undergo antituberculosis treatment. When species identi cation tests are unavailable or not conducted, patients are not suspected to have NTM infections until they are not susceptible to anti-tuberculosis drugs, often resulting in undesirable side effects and heavy nancial burdens [7,8]. Therefore, early differential diagnosis of NTM is particularly important in the clinical practice, which may have a signi cant impact on the prognosis of the disease.Although there have been many studies on the clinical characteristics of NTM, but few predictive models have been established, and most of them have to rely on the conventional culture results for diagnosis, the time required is about 4-8 weeks. In the present study, we retrospectively analyzed the clinical characteristics of AFB smear-positive patients with mycobacteriosis admitted to the Respiratory Department of Shanghai Pulmonary Hospital, in...