What factors help differentiate non-tuberculous mycobacterial disease from tuberculosis in patients?

Non-tuberculous mycobacterial (NTM) lung disease can look very similar to pulmonary tuberculosis (TB) on symptoms and chest imaging, but the treatments are completely different. Doctors use a combination of patient history, lab tests, and CT scan features to tell them apart. Key clues include older age, certain underlying lung conditions, and a negative TB blood test (IGRA).

What the research says

Several studies have identified factors that help distinguish NTM lung disease from TB. A 2024 study found that patients with NTM were more likely to have diabetes, bronchiectasis, chronic obstructive pulmonary disease (COPD), and lung cavities on CT scans compared to TB patients ⁹. Another study from 2023 reported that NTM patients were significantly older and had a lower rate of positive TB-IGRA (a blood test for TB infection) ¹⁰. The same study also found that NTM patients had lower absolute counts of B lymphocytes, a type of immune cell ¹⁰. A 2025 study added that symptoms like cough with sputum and hemoptysis (coughing up blood), as well as CT findings of thin-walled cavities and centrilobular nodules, were more common in NTM, while bronchiectasis and diabetes were again confirmed as risk factors ¹¹. Importantly, the 2025 study developed a diagnostic model that achieved 82.5% sensitivity and 85.5% specificity in distinguishing NTM from TB ¹¹.

What to ask your doctor

• Could my age and any history of bronchiectasis, COPD, or diabetes make NTM more likely than TB?
• Should I have a TB-IGRA (interferon-gamma release assay) blood test to help rule out TB?
• Would a high-resolution CT scan of my chest help look for thin-walled cavities or other NTM-specific patterns?
• If my sputum culture grows mycobacteria, will the lab do species identification to confirm NTM versus TB?
• Are there any immune system tests, like lymphocyte counts, that could support the diagnosis?