The Prevalence Rate of Tuberculin Skin Test Positive by Contacts Group to Predict the Development of Active Tuberculosis After School Outbreaks.
BACKGROUND
The tuberculin skin test (TST) is the standard tool to diagnose latent tuberculosis infection (LTBI) in mass screening. The aim of this study is to find an optimal cut-off point of the TST+ rate within tuberculosis (TB) contacts to predict the active TB development among adolescents in school TB outbreaks.


METHODS
The Korean National Health Insurance Review and Assessment database was used to identify active TB development in relation to the initial TST (cut-off, 10 mm). The 7,475 contacts in 89 schools were divided into two groups: Incident TB group (43 schools) and no incident TB group (46 schools). LTBI treatment was initiated in 607 of the 1,761 TST+ contacts. The association with active TB progression was examined at different cut-off points of the TST+ rate.


RESULTS
The mean duration of follow-up was 3.9±0.9 years. Thirty-three contacts developed active TB during the 4,504 person-years among the TST+ contacts without LTBI treatment (n=1,154). The average TST+ rate for the incident TB group (n=43) and no incident TB group (n=46) were 31.0% and 15.5%, respectively. The TST+ rate per group was related with TB progression (odds ratio [OR], 1.025; 95% confidence interval [CI], 1.001-1.050; p=0.037). Based on the TST+ rate per group, active TB was best predicted at TST+ ≥ 16% (OR, 3.11; 95% CI, 1.29-7.51; area under curve, 0.64).


CONCLUSIONS
Sixteen percent of the TST+ rate per group within the same grade students can be suggested as an optimal cut-off to predict active TB development in middle and high schools TB outbreaks.
Korean Institute of Tuberculosis, Cheongwon, Korea.
Hee Jin
HJ
Kim
Department of Preventive Medicine, Korea University College of Medicine, Seoul, Korea.
Byung Chul
BC
Chun
SRC, Department of Statistics, Seoul National University, Seoul, Korea.
AmyM
A
Kwon
Korean Institute of Tuberculosis, Cheongwon, Korea.
Gyeong-Ho
GH
Lee
Korean Institute of Tuberculosis, Cheongwon, Korea.
Sungweon
S
Ryu
Korean Institute of Tuberculosis, Cheongwon, Korea.
Soo Yeon
SY
Oh
Korean Institute of Tuberculosis, Cheongwon, Korea.
Jin Beom
JB
Lee
Health Insurance Review and Assessment Service, Seoul, Korea.
Se Hwa
SH
Yoo
Public Healthcare Center, Ansan, Korea.
Eui Sook
ES
Kim
Division of Pulmonary, Sleep, and Critical Care Medicine, Department of Internal Medicine, Korea University Ansan Hospital, Korea University College of Medicine, Ansan, Korea.
Je Hyeong
JH
Kim
Division of Pulmonary, Sleep, and Critical Care Medicine, Department of Internal Medicine, Korea University Ansan Hospital, Korea University College of Medicine, Ansan, Korea.
Chol
C
Shin
Division of Pulmonary, Sleep, and Critical Care Medicine, Department of Internal Medicine, Korea University Ansan Hospital, Korea University College of Medicine, Ansan, Korea.
Seung Heon
SH
Lee
Adolescent; Disease Outbreaks; Latent Tuberculosis; Tuberculin Test; Tuberculosis