Analysis of Interferon-Gamma Release Assay Results for Latent Tuberculosis Infection Diagnosis at a Referral Clinical Laboratory in South Korea

The world health organization states that individuals with Latent Tuberculosis Infection (LTBI) are infected with Tuberculosis (TB) bacteria but do not show symptoms of active disease. However, they are at possibility of developing vigorous TB and potentially transmitting the illness to others. In 2018, South Korea reported a 14.8% positivity rate in LTBI screening, with higher rates observed among older individuals, those with lower incomes and women. Furthermore, approximately one in four people worldwide has LTBI. LTBI within certain groups is often the result of prolonged, cumulative and close contact with infected individuals. In this study, we aimed to analyze the current scenario regarding LTBI in South Korea, where large groups are being tested utilizing the Interferon-Gamma Release Assay (IGRA). From 2019-2022, 219,459 cases with IGRA results obtained from a referral clinical laboratory in Yongin city were investigated. This research was accepted by the Institutional Review Board (IRB) of Dankook university. The specimens were collected in QuantiFERON® gold plus Tubes (TB) (Qiagen GmbH, Hilden, Germany) and interferon-gamma activity was measured using an enzyme-linked immunosorbent assay (Dynex technologies, Inc., Chantilly, Virginia, USA). multinomial logistic regression analysis was performed to study the association among age, sex and LTBI confirmed by IGRAs. The p-value for sex was less than 0.001, indicating a significantly higher positivity rate in women than that in men. Additionally, the positivity rate decreased in both sexes from 2019-2022. Notably, the highest positivity rates were observed in 50-59-year age set, with men at 1.32% and women at 2.33%. As testing frequency increased, the probability of detecting positive results also increased. Continuous IGRA testing is recommended for individuals in the 50-59-year age group. Regular and extensive testing is recommended for healthcare workers, military personnel, prisoners and students. Therefore, the pros and cons of IGRA can be analyzed and it is believed that it can be helpful for public health.