Lessons learned from continued TB outbreaks in a high school.

Young Kim,Jae Hyung Cha,Je Hyeong Kim,Eui Sook Kim,Yoon Soo Chang,Hong Jo Choi,Byeong Ki Kim,Chol Shin,Sung Weon Ryu,Seung Heon Lee,Hee Jin Kim

doi:10.1371/journal.pone.0188076

Young Kim, Jae Hyung Cha + Show 9 more

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https://doi.org/10.1371/journal.pone.0188076

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Abstract

We investigated the aftereffects of confirmatory QuantiFERON testing (QFT) added to a positive tuberculin skin test (TST). We reviewed the pre and post course of sequential tuberculosis (TB) outbreaks in a high school where massive 43 active TB cases had been found within one year before delayed contact investigation. And we investigated the TB development in relation to initial TST and QFT during mean follow-up of 3.9 ± 0.9 years. After delayed contact investigation for two subsequent TB outbreaks, 925 contacts were divided into the following 3 groups: TST- (n = 632), TST+/QFT+ (n = 24), TST+/QFT- (n = 258). QFT- was more prevalent than QFT+ in contacts with 10mm ≤ TST <15mm (158, 61.2%) compared with TST ≥15mm (100, 38.8%) among the TST+ reactors (P < 0.001). Among the 258 TST+/QFT- subjects, 256 received no latent TB infection (LTBI) treatment, but 7 contacts developed TB during follow-up. Among these 7 patients, 4 had initial TST ≥15mm and 3 had 10mm ≤ TST <15mm. In conclusion, the delayed contact investigation for LTBI in a high school resulted in continued TB developments. False-negative QFT performed late among the TST+ reactors should not be considered criteria for LTBI treatment. Additionally, the contacts only with TST ≥15mm should be considered for LTBI treatment in congregate settings of intermediate-burden countries.

Highlights

To eliminate tuberculosis (TB), rapid diagnosis and treatment of infectious TB patients in TB high-burden countries and control of latent TB infection (LTBI) for TB contacts in low-burden countries are important main strategies [1,2]
We identified the disadvantages of the two-step strategy and the meaning of strong positive TST results after a TB outbreak in congregate settings such as high schools
Using the data from the 2005–2007 TB outbreaks, we reviewed the TB outbreak courses of a high school and identified the TB development associated with the initial TST and QuantiFERON testing (QFT) results using the Korean national claims database

Summary

Introduction

To eliminate tuberculosis (TB), rapid diagnosis and treatment of infectious TB patients in TB high-burden countries and control of latent TB infection (LTBI) for TB contacts in low-burden countries are important main strategies [1,2]. How to control LTBI in intermediate-burden countries such as South Korea where the incidence rate of active TB is 80/100,000 [3] is not well understood, WHO recommends the tuberculin skin test (TST) and interferon-gamma release assay (IGRA) guidelines based on TB burden with a cut-off level of 100/100,000 that discriminates the high from low burden in addition to economic status [4,5].

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