Screening for latent tuberculosis infection in South Korean healthcare workers using a tuberculin skin test and whole blood interferon-γ assay

Abstract

This study compared the results of a tuberculin skin test (TST) and a whole-blood interferon-gamma release assay (IGRA) to screen latent tuberculosis (TB) infection (LTBI) according to risk of TB exposure in South Korea. A cross-sectional comparison of 82 healthcare workers (HCWs) was performed from June 2009 to January 2010. Participants were grouped according to their risk for TB exposure: group 1, frequent and direct contact with active TB patients (n = 35); group 2, no known history of direct contact with active TB patients (n = 47). For the TST (10-mm induration cut-off), the positive response rate was 42.9% in group 1 and 34.0% in group 2 (p = 0.42). For the IGRA, the positive response rate was 40% in group 1 and 10.6% in group 2 (p = 0.002). Results obtained from the TST and the IGRA were not in significant agreement. The working duration of HCWs in TB-related departments was the only significant risk factor for LTBI (odds ratio 1.03; p = 0.031). Further, the IGRA can more accurately discriminate LTBI compared to the TST, based on the risk of TB exposure. These results suggest that the IGRA is diagnostically useful for LTBI in South Korean HCWs.

Prevalence of Latent Tuberculosis Infection among Health Care Workers in South Korea: A Multicenter Study

“…Our study showed poor agreement between the TST and the QFT-GIT, which is consistent with previous reports6,12. In South Korea, where BCG vaccination is mandatory, children are vaccinated with BCG at birth; until 1997, TST non-responders were revaccinated again at age 12 or 13 years13.…”

“…The statistically significant association between the experience of working in TB-related departments and a positive LTBI result on QFT-GIT and not on TST in our study supports the above hypothesis. This assumption was also made in previous studies which were conducted in South Korea6,9,12 as well as in other countries4,14,15. Moreover, while the positive rate of the TST in the present study was not different from that in the general population, the positive QFT-GIT rate was significantly higher than that in general population in South Korea (unpublished data).…”

“…HCWs working in TB-related departments (pulmonary department, medical intensive care unit, emergency room [ER], etc. ), particularly nurses, have been reported to be at a higher risk of developing TB than other occupational subgroups of HCWs due to increased possibility of nosocomial transmission3-6.…”

“…In South Korea, an intermediate TB-burden country (92/100,000 general population), several studies have shown that the prevalence of latent TB infection (LTBI) among nurses was higher than in the general population6,7. In addition, one study reported that nurses working in TB-related departments had approximately five-fold higher risk for TB development than the general population8, which indicates that LTBI remains a serious health problem among specific subgroups of HCWs in South Korea.…”

“…In order to implement stricter preventive measures, the exact prevalence of LTBI among HCWs, particularly nurses and doctors, and its risk factors should be obtained. To date, however, all studies on LTBI among HCWs have been performed at single center only6-9. In addition, no study has been conducted to address risk factors influencing LTBI prevalence in South Korea.…”