From the Guidelines
A positive QuantiFeron-TB Gold test in a patient with Mycobacterium avium-intracellulare (MAI) infection is likely a false positive result, and clinicians should consider the possibility of concurrent latent tuberculosis infection or cross-reactivity between MAI and tuberculosis antigens. According to the guidelines for using the QuantiFeron-TB test for diagnosing latent Mycobacterium tuberculosis infection 1, the test is not recommended for the diagnosis of M. avium complex disease. Key points to consider in this scenario include:
- Cross-reactivity between MAI and tuberculosis antigens can lead to false positive QuantiFeron results
- Patients with confirmed MAI and a positive QuantiFeron test should be evaluated for concurrent latent tuberculosis infection, especially if they are at high risk
- Additional evaluation may include clinical history, chest imaging, and possibly sputum cultures for tuberculosis to distinguish between cross-reactivity and true co-infection
- Treatment decisions should be based on the complete clinical picture, with MAI infection typically requiring a multi-drug regimen including macrolides, ethambutol, and rifampin, and latent tuberculosis requiring different management, usually with isoniazid, rifampin, or other appropriate regimens. The approach to using QuantiFeron for initial screening, followed by QuantiFeron and TST 3 months after the end of the suspected exposure, has not been evaluated 1, highlighting the need for careful consideration of test results in the context of MAI infection.
From the Research
Quantiferon Positive in MAI
- The QuantiFERON-TB GOLD In-Tube test is used to detect infection with Mycobacterium tuberculosis, but it can also be positive in patients with Mycobacterium avium complex (MAI) disease 2.
- A study found that 11.3% of patients with MAI disease showed a positive response with QuantiFERON-TB GOLD In-Tube, and these patients were mostly elderly with a history of pulmonary tuberculosis 2.
- The test's positive response rate in MAI patients is not well understood, but it is thought to be related to the patient's immune response and history of tuberculosis infection 2.
- Other studies have focused on the treatment of MAI disease, including the use of antimycobacterial drugs such as clarithromycin, azithromycin, and rifabutin 3, 4, 5, 6.
- These studies have shown that combination therapy with multiple drugs is often effective in treating MAI disease, but the optimal treatment regimen is still being researched 3, 4, 5.