Interferon Gamma Release Assay for Latent Tuberculosis Screening in High TB-Endemic Region: A Retrospective Study

Introduction: Tuberculosis (TB) remains a significant public health challenge, particularly in high-endemicity settings where latent TB infections (LTBI) contribute to ongoing transmission. Early identification and management of LTBI are crucial in limiting the spread of the disease. This study demonstrates the role of Interferon Gamma Release Assay (IGRA) as a screening tool for latent tuberculosis in high-burden region. Materials and Methods: This retrospective observational study assessed the detection of LTBI using the QuantiFERON-TB Gold Plus (QFT-Plus) test among 145 patients at the Department of Microbiology & Immunology, Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh, from August 2023 to August 2024. The study included patients suspected of TB, those screened before immunosuppressive therapy, organ transplantation, or kidney dialysis. Participants were tested IGRA using QFT-Plus, which detects interferon-gamma (IFN-γ) released in response to Mycobacterium tuberculosis antigens. Results and Discussion: Among 145 patients tested for the QFT-Gold Plus test, 55.17% (n = 80) were positive for LTBI, with a substantial agreement between TB1 and TB2 responses (p < 0.05). Among the study population, 71 (49%) were male, while 74 (51%) were female. The median age of the participants was 37 (5 - 88 years). About 139 of them were BCG vaccinated and all of them were known to be HIV-negative. Notably, 70% of LTBI-positive cases showed a TB1 response, while 22.5% had positive results for both TB1 and TB2. Most patients tested for LTBI were suspected TB cases (122 patients), accounting for approximately 85% of the total. A smaller portion of patients underwent screening before medical procedures such as dialysis (15 patients or 10%) and transplant (8 patients or 5%). Night sweats were the most common symptoms (55.7%), followed by cough and weight loss. Chest X ray findings were negative for all the patients. Conclusion: The results highlight that QFT-Plus may be utilized as a useful diagnostic screening tool for latent TB in regions with a high disease burden, though challenges related to cost and infrastructure persist. With growing global efforts to eliminate tuberculosis, focused screening and treatment of LTBI in high-risk groups could play a vital role in reducing the progression of TB. The study underscores the importance of targeted screening for LTBI to reduce the progression to active TB, particularly in resource-limited settings.