Diagnostic value of interferon-gamma release assay in the diagnosis of tuberculosis infection before the use of TNF-alpha blocker in pediatric rheumatology patients

Aim: Tuberculin skin test (TST) has been used for many years in the early diagnosis of latently infected cases with Mycobacterium tuberculosis. In recent years, interferon-gamma (IFN - γ) based tests have emerged as a new diagnostic tool in the diagnosis of latent tuberculosis infection. In this study, we aimed to investigate the diagnostic value of Interferon-γ Release Assey (IGRA) in the diagnosis of latent tuberculosis infection (LTBI) in pediatric patients who were indicative of juvenile idiopathic arthritis, enthesitis-related arthritis, psoriatic arthritis, autoimmune uveitis and adenosine deaminase 2 enzyme deficiency, in patients with Indication of Tumor Necrosis Factor-α (TNF-α) Materials and methods: In this study, 99 children, who were followed up in the Department of Pediatric Rheumatology at Çukurova University Faculty of Medicine between 2017-2019, we were evaluated retrospectively to investigate before the use of TNF-α blocker. Demographic, clinical, radiological and laboratory features of the patients, TST and IGRA results, and INH (isoniazid) onset rates were recorded in the research papers. Demographic, clinical and laboratory features, diagnosis of rheumatological disease, treatments used before TNF-α blocker and chest radiograph findings were evaluated with TST and IGRA results. In 99 patients, in which the IGRA and TST tests were applied together, the compatibility between the two test results was evaluated. TST test was done with the Mantoux method. Quantiferon-TB Gold Plus device was used for the IGST test. The data were analyzed using SPSS version 20.0 program. Results: Both TST and IGRA tests were applied to 99 patients examined in this study. Of the nineteen patients, 19 (19.2%) had positive results of TST and 4 (4%) had positive results. 17 patients (17.2%) with a positive TST result (≥5 mm) and a negative IGRA result were detected. 2 (2%) patients with negative TST (<5 mm) and positive IGRA results were detected. The number of TST positive and IGRA positive patients was 2 (2%). The compatibility rate of both tests was determined as 12%. The agreement of both tests was not statistically significant (p=0.110, kappa=0.115). BCG vaccination times were cataloged as <5 years, 5-10 years, ≥10 years. There was no statistically significant difference between BCG vaccination time and TST (p=0.243). No statistically significant relationship was found between patients with JIA and non-JIA and TST positivity (p>0.999). No statistically significant difference was found between patients diagnosed with JIA and non-JIA patients and IGRA positivity (p>0,999). No relation was found between TST and IGRA results, gender, age, BCG vaccination, TB contact history, diagnosis of rheumatological disease, chest radiograph findings. There was no statistically significant relationship between the use of methotrexate and the positivity of TST and IGRA (p> 0.05). Discussion: All patients should be screened for latent tuberculosis infection before the use of TNF-α blocker. TST and IGRA tests can be used for screening. However, BCG vaccine affects TST result, and specificity and sensivity of TST decreases in BCG vaccines. In addition, it is considered to be more accurate to prefer IGRA in immunosuppressive conditions such as anti-TNF treatment. However, in order to reach this opinion, studies evaluating more cases are needed. Keywords: Interferon-gamma release assay, tuberculin skin test, tuberculosis infection, tumor necrosis factor-α blocker