Background: We evaluated the prevalence and risk factors associated with latent tuberculosis infections (LTBIs) among healthcare workers (HCWs) working in non-TB departments in a tertiary referral hospital.
Methods: This study was carried out at Severance Hospital, a tertiary hospital in South Korea with 2442 beds. The study subjects were 2228 HCWs who did not have any previous screening records of tuberculin skin tests (TSTs) and interferon-gamma release assays (IGRAs) or histories of tuberculosis. The LTBI screening was performed using both TST and IGRA from May to August 2017. Among the participants, we excluded four whose IGRA results were indeterminate, three with only TST, and 35 who had only IGRA. The prevalence of LTBI and related risk factors for LTBI were analyzed.
Results: The mean age of the participants was 41.3 years. Females comprised 66.2% of the sample. The positive proportions of TST (≥10 mm) and IGRA were 35.2% (770/2186) and 29.0% (637/2186), respectively. Among the 2186 participants, 18.8% showed positive results for both TST and IGRA, and the agreement of the two tests was low (kappa=0.390). The frequencies of TST and IGRA positivity increased with age. Multiple regression analysis indicated age and spontaneously healed TB lesions on chest X-ray were associated with positive TST and IGRA results.
Conclusion: Based on TST and IGRA in a tertiary referral hospital, the prevalence of LTBI among HCWs not involved in the care of patients with TB was considerable. Although age and spontaneously healed TB lesions on chest X-ray were the related factors for the positivity of TST and IGRA, we need to check the risk of TB exposure in hospitals and communities.

Keywords: Latent tuberculosis infection, Healthcare workers, Tuberculin skin test, Interferon- gamma release assay