From the Guidelines
Repeat QuantiFERON Testing for TB Monitoring
Repeat QuantiFERON testing is not generally necessary for monitoring tuberculosis (TB) in individuals who have already tested positive, as it does not provide additional information on treatment response or disease activity 1.
Exceptions and Considerations
However, there are exceptions where repeat testing may be considered, such as in individuals with recent contact with persons who have infectious TB, where a negative QuantiFERON result should be confirmed with a repeat test performed 8-10 weeks after the end of exposure 1. Additionally, for individuals at high risk of TB exposure, such as those traveling to or working in areas with high TB prevalence, yearly testing for latent TB (including QuantiFERON) may be recommended 1.
Diagnostic Approach
In cases where repeat testing is necessary, a different diagnostic approach, such as the tuberculin skin test (TST) or a repeat QuantiFERON test with a different antigen preparation, may be used to minimize the risk of false-negative results 1. Clinical evaluation, chest radiographs, and sputum smear microscopy or culture should be used to monitor TB treatment response, rather than relying solely on QuantiFERON test results.
Frequency of Testing
The QuantiFERON test should not be repeated more frequently than every 3 months, and only when clinically indicated. Patients who test positive for TST or IGRA at baseline are expected to remain positive for these tests even after successful treatment of TB, and therefore, repeating tests will not help in diagnosis of recurrent TB 1.
Key Points
- Repeat QuantiFERON testing is not necessary for monitoring TB in individuals who have already tested positive.
- Exceptions include recent contact with infectious TB, high-risk individuals, and immunocompromised patients.
- A different diagnostic approach may be used for repeat testing to minimize false-negative results.
- Clinical evaluation and other diagnostic tools should be used to monitor TB treatment response.
From the Research
Repeat QuantiFERON (IGRA) Testing for Tuberculosis (TB) Monitoring
- The necessity of repeat QuantiFERON testing for TB monitoring is a topic of discussion among researchers, with some studies suggesting that it may not be necessary in all cases 2, 3.
- A study published in 2013 found that repeated testing within ten weeks yielded negative reactivity in 69% of patients with weakly positive results, suggesting that repeat testing may be useful in certain cases 2.
- Another study published in 2017 found that the QuantiFERON-TB Gold In-Tube test was useful in diagnosing tuberculosis and monitoring the response to anti-tuberculosis treatment, but the results were not consistent across all patients 4.
- A study published in 2010 found that most patients remained QuantiFERON-TB positive after preventive therapy, suggesting that the test should not be used to monitor the effect of preventive therapy 3.
- A study published in 2008 found that the positive rate of QuantiFERON TB-2G test results decreased over time after the initiation of treatment, but the test may not be useful in monitoring the cure of TB infection 5.
- A review published in 2016 discussed the pros and cons of the QuantiFERON test for the diagnosis of tuberculosis, prediction of disease progression, and treatment monitoring, highlighting the need for further research to improve the sensitivity and specificity of the test 6.
Key Findings
- Repeat QuantiFERON testing may be useful in certain cases, such as in patients with weakly positive results or in monitoring the response to anti-tuberculosis treatment 2, 4.
- The test may not be useful in monitoring the effect of preventive therapy or the cure of TB infection 3, 5.
- The QuantiFERON test has advantages and limitations depending on the type of population studied, and further research is needed to improve its sensitivity and specificity 6.
Test Characteristics
- The QuantiFERON test has a sensitivity of 74.4-80.5% and a specificity of 57.1-66.2% for the detection of pulmonary tuberculosis, depending on the cut-off point used 4.
- The test has a positive predictive value that is not better than that of the tuberculin skin test for the progression to TB among immigrant close contacts 6.