Tuberculin Skin Test and Boosted Reactions among Newly Employed Healthcare Workers: An Observational Study

Song Yee Kim,Joon Chang,Moo Suk Park,Hyun Sook Kim,Kyungwon Lee,Young Ae Kang,Se Kyu Kim,Dongeun Yong,Young Sam Kim,Madhukar Pai

doi:10.1371/journal.pone.0064563

Abstract

ObjectiveTo evaluate the prevalence of and factors associated with latent tuberculosis infection (LTBI) based on the tuberculin skin test (TST) and to estimate the boosted reaction rate among newly employed healthcare workers (HCWs).DesignNewly employed HCWs between January 2010 and July 2012 at Severance Hospital in South Korea were enrolled in this study. A one-step TST was conducted before October 2011, and a two-step TST after October 2011.ResultsOf 2132 participants, 778 (36.5%) had positive TST results. Being older (odds ratio [OR] 1.10, 95% confidence interval [CI] 1.06–1.13, P<0.001), male (OR 1.78, 95% CI 1.21–2.62, P = 0.003), rejoining the hospital workforce (OR 1.58, 95% CI 1.04–2.40, P = 0.032), and having a previous history of tuberculosis (TB) (OR 18.21, 95% CI 2.15–154.10, P = 0.008) during the one-step period, and being older (OR 1.15, 95% CI 1.10–1.21, P<0.001) during the two-step period were significantly associated with a positive TST. A two-step TST was performed in 556 HCWs, and a boosted reaction was observed in 79 (14.2%). The induration size on the first TST (5–9-mm group) was the only factor associated with a boosted reaction on the second TST.ConclusionsThe prevalence of LTBI based on the TST among newly employed HCWs was high. The boosted reaction rate on two-step TST was not low; therefore, the use of two-step TST may be necessary for regular monitoring in countries with an intermediate TB burden and a high rate of Bacillus Calmette-Guérin vaccination.

Highlights

It has long been recognized that healthcare workers (HCWs) are at high risk of a Mycobacterium tuberculosis
Because repeated testing is needed for monitoring, an evaluation of boosted reactions is important among HCWs in areas with a high TB burden and where Bacillus CalmetteGuerin (BCG) vaccination is mandatory
Boosted Reaction and Associated Factors A two-step TST was performed in 556 HCWs, and a boosted reaction was observed in 79 (14.2%)

Summary

Introduction

It has long been recognized that healthcare workers (HCWs) are at high risk of a Mycobacterium tuberculosis To control tuberculosis (TB) among HCWs, routine screening and appropriate treatment for latent TB infections (LTBIs) are recommended [3]. A boosted reaction may occur on repeated testing, which can cause misinterpretation as a conversion of the TST [4]. A boosted reaction is regarded as correlated with the initial TST reaction and Bacillus CalmetteGuerin (BCG) vaccination [1,4,5,6]. Because repeated testing is needed for monitoring, an evaluation of boosted reactions is important among HCWs in areas with a high TB burden and where BCG vaccination is mandatory

Methods

Results

Discussion

Conclusion