The elimination of tuberculosis (TB) in the US relies on effective tests to detect individual risk of developing the disease, aiding in preventive interventions. However, the comparative performance of available TB tests—specifically, the tuberculin skin test (TST) and two interferon- gamma release assays (IGRAs)—in predicting TB disease development remains uncertain. In high-risk populations, accurate prediction of TB disease development is crucial for timely intervention and prevention strategies.
While the TST and IGRAs are commonly used diagnostic tools, their relative performance in predicting incident TB in the US has not been well-established. A recent study was published in the journal JAMA Network Open. The study was conducted by Traycy A. and colleagues. This prospective diagnostic study aimed to compare the performance of the TST with two IGRAs, QuantiFERON-TB Gold In-Tube (QFT-GIT) and SPOT.TB (TSPOT), in predicting TB disease in high-risk populations.
The study enrolled participants at 10 US sites between 2012 and 2020 who were at high risk of TB infection or progression to disease. Participants underwent concurrent testing with the TST and two IGRAs at enrollment. Incident TB cases were diagnosed more than 30 days after enrollment. Data analysis was performed in June 2023.
The key findings of the study were as follows:
•A total of 22,020 eligible participants were included, with a median follow-up of 6.4 years.
• Tuberculosis disease was identified in 129 case patients, with 42 having incident TB and 87 prevalent TB.
• Both IGRAs, TSPOT and QFT-GIT, performed significantly better than the TST in predicting incident TB, with positive predictive value (PPV) ratios of 1.65 and 1.47, respectively.
• There was a statistically significant incremental gain in PPV when a positive TST result was known, with positive QFT-GIT and TSPOT results.
The study concluded that IGRAs demonstrated superior performance for predicting incident TB compared to the TST. Additionally, IGRAs provided a statistically significant incremental improvement in PPV when combined with a positive TST result. These findings suggest that IGRAs may enhance decisions to treat TB infection and prevent TB disease.
The results underscore the importance of utilizing IGRAs in high-risk populations for accurate prediction of TB disease development, thereby enabling timely interventions to prevent TB transmission and improve patient outcomes.
Reference:
Ayers, T., Hill, A. N., Raykin, J., Mohanty, S., Belknap, R. W., Brostrom, R., Khurana, R., Lauzardo, M., Miller, T. L., Narita, M., Pettit, A. C., Pyan, A., Salcedo, K. L., Polony, A., Flood, J., Pascopella, L., Ahmed, A., Aiona, K., Lovato, J., … CDC Tuberculosis Epidemiologic Studies Consortium. (2024). Comparison of tuberculin skin testing and interferon-γ release assays in predicting tuberculosis disease. JAMA Network Open, 7(4), e244769. https://doi.org/10.1001/jamanetworkopen.2024.4769