From the Guidelines
A QuantiFeron TB Plus result that is "intermediate" or "abnormal" typically indicates a possible Mycobacterium tuberculosis infection that requires further evaluation, and you should consult with a healthcare provider promptly for a complete assessment. This assessment will likely include a chest X-ray and physical examination to determine if you have active tuberculosis disease or latent tuberculosis infection (LTBI) 1. If diagnosed with LTBI, the standard treatment is isoniazid 300mg daily for 9 months, or a shorter regimen of isoniazid plus rifapentine weekly for 12 weeks, as these regimens have been shown to be effective in preventing the progression to active TB disease 1. Alternative regimens include rifampin 600mg daily for 4 months. Treatment is important because approximately 5-10% of people with LTBI will develop active TB disease if not treated, with higher risk in the first two years after infection 1. The QuantiFeron test measures immune response to TB proteins, and intermediate results can occur due to immunosuppression, recent TB exposure, or technical factors in the testing process 1. Regular follow-up during treatment is essential to monitor for medication side effects, particularly liver function.
Some key points to consider in the management of a patient with an intermediate or abnormal QuantiFeron TB Plus result include:
- The need for a comprehensive medical evaluation to rule out active TB disease before initiating treatment for LTBI 1
- The importance of considering the patient's epidemiologic and medical history, as well as other clinical information, when interpreting the QuantiFeron TB Plus result 1
- The potential for false-positive results, particularly in individuals with a low likelihood of M. tuberculosis infection 1
- The need for regular follow-up during treatment to monitor for medication side effects and to assess treatment efficacy 1
Overall, the management of a patient with an intermediate or abnormal QuantiFeron TB Plus result requires a thorough and individualized approach, taking into account the patient's unique clinical circumstances and medical history 1.
From the Research
Quantiferon TB Plus Results Intermediate Abnormal
- The QuantiFERON-TB Gold test is used to detect immune reactivity towards Mycobacterium tuberculosis 2, 3.
- Intermediate abnormal results on the QuantiFERON-TB Gold test may indicate a weakly positive response, which can be seen in individuals with immune-mediated diseases or pulmonary outpatients with suspected tuberculosis infection 3.
- A study found that 26% of all positive QuantiFERON-TB Gold test results were weakly positive, and repeated testing within ten weeks yielded negative reactivity in 69% of these patients 3.
- Predictive factors for indeterminate results on the QuantiFERON test include severe lymphopenia, chronic renal disease, autoimmune disease, and chronic lung disease 4.
- The QuantiFERON-TB Gold In-Tube assay has been used to measure interferon-γ response to mycobacterial antigens in adults with positive tuberculin skin test results, and results have shown that IFN-γ levels decline between baseline and the end of isoniazid preventive therapy or observation 5.
- The combined use of QuantiFERON-TB Gold assay and chest computed tomography has been found to be effective in differentiating between active TB, latent TB, and non-infected subjects in a contact investigation 6.