Building a model for the differential diagnosis of non-tuberculous mycobacterial lung disease and pulmonary tuberculosis: A case-control study based on immunological and radiological features

Abstract

Background: Although the incidence of non-tuberculous mycobacterial pulmonary disease (NTM-PD) is increasing annually, it is easily misdiagnosed as pulmonary tuberculosis (PTB). This study aimed to screen and identify the immunological and radiological characteristics that differentiate NTM-PD from PTB and to construct a discriminatory diagnostic model for NTM-PD, providing new tools for its differential diagnosis.

Methods: Hospitalised patients diagnosed with NTM-PD or PTB between January 2019 and June 2023 were included in the study. Immunological and radiological characteristics were compared between the two groups. Based on the selected differential features, a logistic regression algorithm was used to construct a discriminatory diagnostic model for NTM-PD, and its diagnostic performance was preliminarily analysed.

Results: Patients with NTM-PD were significantly older than those with PTB and the tuberculosis-specific interferon-gamma release assay (TB-IGRA) positivity rate was significantly lower in the NTM-PD group. Moreover, the absolute counts of total T lymphocytes, CD4⁺ T lymphocytes, CD8⁺ T lymphocytes, NK cells, and B lymphocytes were significantly lower in patients with NTM-PD and PTB than in healthy controls. Additionally, patients with NTM-PD had a significantly lower absolute count of B lymphocytes than the PTB group. Radiological analysis revealed significant differences between patients with NTM-PD and PTB in terms of cavity wall thickness, bronchial dilation, lung consolidation, pulmonary nodule size, pulmonary emphysema, lung bullae, lymph node calcification, pleural effusion, mediastinal and hilar lymphadenopathy, and the tree-in-bud sign. Bronchial dilation was identified as the predominant risk factor of NTM-PD, whereas TB-IGRA positivity, lymph node calcification, pleural effusion, and mediastinal and hilar lymphadenopathies were protective factors. Based on this, we constructed a discriminatory diagnostic model for NTM-PD. Its receiver operating characteristic curve demonstrated good diagnostic performance, with an area under the curve of 0.938. At the maximum Youden index of 0.746, the sensitivity and specificity were 0.835 and 0.911, respectively.

Conclusions: Patients with NTM-PD and PTB exhibited impaired humoral and cellular immune functions as well as significant differences in radiological features. The constructed NTM-PD diagnostic model demonstrated good diagnostic performance. This study provides a new tool for the differential diagnosis of NTM-PD.

Keywords: Diagnostic model; Imaging features; Non-tuberculous mycobacterial pulmonary disease (NTM-PD); Pulmonary tuberculosis (PTB); Tuberculosis-specific interferon-gamma release assay (TB-IGRA).