Mycobacterial Diseases O-015 : Predictive Value of Age for Latent Tuberculosis Infection among Healthcare Workers at a Tertiary Hospital in Korea

Purpose Healthcare workers (HCWs) are at high risk of tuberculosis (TB) infection due to their occupational exposure. Many guidelines recommended to perform routine screening for latent tuberculosis infection (LTBI) of HCWs to receive appropriate treatment. This study aimed to identify the risk factors of positive interferon-gamma (IFN-γ) release assay (IGRA) of HCWs in intermediate TB burden country. Methods This was a retrospective study in a tertiary hospital in South Korea. Form May 2017 to March 2018, HCWs were tested IGRA. We estimated the prevalence of TB infection and the annual risk of TB infection (ARI) based on their IGRA Results according to age group. Multivariate logistic regression analysis was performed to evaluate the risk factors for IGRA positivity. High-risk departments were defined as TB related departments. Results Total 3233 HCWs were analyzed. Median age of participants was 38.0 and female was predominant (72.6%). Overall positive rate of IGRA was 24.1%. According to age group, IGRA positive rates were 6.6% in the 20s, 14.4% in the 30s, 34.3% in the 40s, and around 50% in the 50s and 60s, respectively. The ARIs were 0.349% - 0.034% between 1986 and 2005, midyear of TB infection, have gradually decreased over approximately three decades. The area under the curve (AUC) predicting LTBI using IGRA was 0.749 with age cut-off point at 40. In multivariate analysis, older age, healed TB lesion in x-ray, male gender were risk factors of IGRA positivity, whereas high-risk TB department was not a significant risk factor for positive IGRA Results. Conclusions This study suggests that in intermediate TB burden countries, the LTBI test Result of HCWs might be greatly affected by age itself, rather than occupational exposure, thus careful interpretation considering the age structure is required.