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. 2017 Nov 16;12(11):e0188076.
doi: 10.1371/journal.pone.0188076. eCollection 2017.

Lessons learned from continued TB outbreaks in a high school

Young Kim  1   2 , Byeong Ki Kim  1 , Hong Jo Choi  3 , Sung Weon Ryu  3 , Eui Sook Kim  4 , Yoon Soo Chang  2 , Hee Jin Kim  3 , Jae Hyung Cha  5 , Je Hyeong Kim  1 , Chol Shin  1 , Seung Heon Lee  1
Affiliations

Lessons learned from continued TB outbreaks in a high school

Young Kim et al. PLoS One. .

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.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Scheme of TB outbreak in a single high school in Korea.
Each symbol in column represents one student and placed at the point at which the student was diagnosed as active TB.● = Active TB cases with positive AFB culture; ○ = Clinical TB cases with negative AFB culture; ▲ = Active TB cases with positive AFB culture and smear developed during follow-up among contacts who were TST+/QFT-; Δ = Clinical TB cases with negative AFB culture developed during follow-up among contacts who were TST+/QFT-; TB = tuberculosis; AFB = acid fast bacilli; TST = tuberculin skin test; QFT = QuantiFERON-TB Gold In-Tube test.
Fig 2
Fig 2. RFLP results of 15 active TB cases with positive AFB culture.
The banding patterns of 15 outbreak strain isolates are completely same. RFLP = restriction fragment length polymorphism; TB = tuberculosis; AFB = acid fast bacilli.
Fig 3
Fig 3. Flow diagram for TB contacts of infectious patients with TB.
All 947 contacts excluding 22 active TB cases were divided into separate groups based on the TST and QFT results. The TB developments of contacts were traced during the mean duration of 3.9 years TB = tuberculosis; TST = tuberculin skin test; QFT = QuantiFERON-TB Gold In-Tube test; LTBI = latent TB infection.
Fig 4
Fig 4. Receiver Operating Characteristic (ROC) curves for prediction of TB cases using different cut-off points of TST induration size.
(A) For all contacts, the overall accuracy was higher with the criteria of TST ≥10 mm than with that of TST ≥15 mm to predict TB cases. (B) But, for the contacts with TST+/QFT- results, the overall accuracy was the most highest with the criteria of TST ≥15 mm. TST = tuberculin skin test; AUC = Area under the curve.
See this image and copyright information in PMC

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