TITLE:
Clinical Evaluation of Two Interferon-Gamma Release Assays for Diagnostic Tests of Tuberculosis Infection in a Tertiary Hospital: Clinical Evaluation of Two IGRAs for TB Infection
AUTHORS:
Yoshihiro Kobashi, Toru Oga
KEYWORDS:
QFT-Plus, T-SPOT.TB, Diagnosis of Tuberculosis, Tertiary Hospital
JOURNAL NAME:
Journal of Tuberculosis Research,
Vol.12 No.3,
August
6,
2024
ABSTRACT: Background: The aim of this study was to evaluate the usefulness of two interferon-gamma release assays (IGRAs) (QuantiFERON-TB Plus (QFT-plus) and T-SPOT.TB assay) for patients suspected of having tuberculosis (TB) infection as supportive methods for diagnosing TB. Patients and Methods: The subjects consisted of 45 patients who required clinical differentiation of TB disease from June 2019 to August 2023. The final clinical diagnoses were: 14 patients with active TB disease, 4 with latent TB infection (LTBI), 17 with old (cured) TB disease, and 10 with pulmonary nontuberculous mycobacterial (NTM) disease. We used the two IGRAs for these patients and evaluated the data according to the manufacturer’s guidelines for interpretation or FDA-approved cutoffs. Results: Among the total of 14 patients with active TB disease (mean age: 64 years old, male: 9, and female: 5), a positive response was noted in 10 patients (71%) on QFT-plus and 9 (64%) on T-SPOT.TB. Four patients with a negative response on QFT-plus and T-SPOT.TB were elderly or cancer patients with lymphocytopenia or hypoalbuminemia. All four patients with LTBI showed a positive response (100%) on both QFT-plus and T-SPOT.TB. Among the seventeen patients with old (cured) TB disease, a positive response was noted in 8 patients (47%) on QFT-plus and 9 (53%) on T-SPOT.TB. All patients with pulmonary NTM disease showed a negative response on both QFT-plus and T-SPOT.TB. Conclusions: A false-negative response on QFT-plus as well as T-SPOT.TB was recognized in elderly patients and patients with an immunosuppressed condition, and half of patients with old (cured) TB showed no negative conversion after the completion of treatment through this study. Although it was recently reported that the positive response rate on QFT-plus of patients with active TB disease was high, we consider it necessary to be careful in diagnosing TB infection using IGRAs for patients with severe underlying diseases in a tertiary hospital based on the results.