• Biomedical Science Letters
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• v.24 no.2
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• pp.138-142
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• 2018

The incidence of tuberculosis (TB) in the Republic of Korea remains high when compared to the incidence in other Organization for Economic Cooperation and Development (OECD) countries. The prompt diagnosis and effective treatment of latent TB infection (LTBI) are very important in terms of controlling the burden of TB. The tuberculin skin test (TST) has long been the "gold standard" assay for the diagnosis of LTBI. However, it can show false positive results due to Bacille Calmette-$Gu{\acute{e}}rin$ (BCG) vaccination and infection with many environmental nontuberculous mycobacteria (NTM). The interferon gamma release assay (IGRA) using Mycobacterium tuberculosis (MTB)-specific antigens, was developed for the detection of LTBI. The QuantiFERON-TB Gold In-Tube assay is one of the most commonly used forms of the IGRA. In order to compare the diagnostic efficacy of the TST and IGRA in relation to LTBI among BCG-vaccinated healthy donors, whole blood samples were collected from 51 participants, and the results of the TST and IGRA were compared. Of the 51 cases, 18 cases (35.3%) were positive and 33 cases (64.7%) were negative when using the TST, while four cases (7.8%) were positive and 47 cases (92.2%) negative when using the IGRA. There was no correlation between the size of the induration in the TST and the $IFN-{\gamma}$ protein level. In conclusion, the TST showed higher cross-reactivity among the BCG-vaccinated healthy participants, therefore, the IGRA might be the most suitable assay for the rapid screening of LTBI in BCG-vaccinated healthy population, or for TB contact investigation.

• Tuberculosis and Respiratory Diseases
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• v.81 no.1
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• pp.59-72
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• 2018

Background: It remains uncertain if $interferon-{\gamma}$ release assays (IGRAs) are superior to the tuberculin skin test (TST) for the diagnosis of active tuberculosis (TB) or latent tuberculosis infection (LTBI) in immunosuppressed populations including people with human immunodeficiency virus (HIV) infection. The purpose of this study was to systematically review the performance of IGRAs and the TST in people with HIV with active TB or LTBI in low and high prevalence TB countries. Methods: We searched the MEDLINE database from 1966 through to January 2017 for studies that compared results of the TST with either the commercial QuantiFERON-TB Gold in Tube (QFTGT) assay or previous assay versions, the T-SPOT.TB assay or in-house IGRAs. Data were summarized by TB prevalence. Tests for concordance and differences in proportions were undertaken as appropriate. The variation in study methodology was appraised. Results: Thirty-two studies including 4,856 HIV subjects met the search criteria. Fourteen studies compared the tests in subjects with LTBI in low TB prevalence settings. The QFTGT had a similar rate of reactivity to the TST, although the first-generation version of that assay was reactive more commonly. IGRAs were more frequently positive than the TST in HIV infected subjects with active TB. There was considerable study methodology and population heterogeneity, and generally low concordance between tests. Both the TST and IGRAs were affected by CD4 T-cell immunodeficiency. Conclusion: Our review of comparative data does not provide robust evidence to support the assertion that the IGRAs are superior to the TST when used in HIV infected subjects to diagnose either active TB or LTBI.

• Korean Journal of Clinical Laboratory Science
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• v.48 no.3
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• pp.225-229
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• 2016

Tuberculosis (TB) is caused by a chronic infectious agent known as Mycobacterium tuberculosis. It is transmitted in airborne particles, called droplet nuclei which was generated by cough, sneeze, shout, or sing of persons who have TB disease. Most infections of TB do not have symptoms, well known as latent tuberculosis infection (LTBI). However, about 10% of LTBI progress to active disease a one or two years after infection. To investigate the LTBI rate of college students who were in contacted with TB patients, we performed chest X-ray, tuberculin skin test (TST) and Interferon-gamma release assay (IGRA) to 74 college students. At a results, 65 students were showed negative and 9 students positive results at chest X-ray and 1st TST test. When confirmed the 65 students who were showed negative by 2st TST, the results showed correctly. But, 9 students who were showed positive results on chest X-ray and 1st TST by IGRA, the only 3 students (4.05%) showed positive results. In conclusion, the LTBI rate in this study showed 4.05% (3/74) and we suggest to investigate other students LTBI rate for decreasing tuberculosis.

• Pediatric Infection and Vaccine
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• v.23 no.2
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• pp.94-101
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• 2016

Purpose: This study aimed to describe the results of a contact investigation on health care workers after exposure to a house officer with smear-positive pulmonary tuberculosis (TB). Methods: Eighty nine out of 101 subjects who had close contact with the index patient agreed to be enrolled in the investigation. The first contact investigation was conducted approximately 30 days after the index patient's onset of symptoms, followed by the second investigation after 10 weeks. In both, clinical manifestations were studied, and chest X-ray and tuberculin skin test (TST)/QuantiFERON-TB Gold (QFT-G) in dual screening strategy were conducted. Results: The first TST resulted in positive in 34 subjects (38.2%). QFT-G was conducted on 16 subjects who tested positive in the first TST and aged under 36. Six of them (37.5%) were positive. The second TST was conducted on 41 subjects with negative results in the first TST. Seventeen (41.5%) were positive and among them, three (17.6%) showed positive QFT-G. None of the subjects were diagnosed with active TB. The probability of TB infection through contact with the index patient was 7.3% (3/41) in dual screening strategy while it was 41.5% (17/41) in TST strategy. Conclusions: This first hospital-setting contact investigation for tuberculosis in Korea revealed that latent tuberculosis infection (LTBI) rates vary depending on different diagnostic strategies. This indicates the need for systematic guidelines for diagnosing LTBI in health care workers who have professional exposure to TB.

• 보건세계
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• v.63 no.1
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• pp.5-7
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• 2014

우리나라 인구의 약 1/3이 결핵에 감염된 것으로 알려져 있다. 많은 사람들이 이 대목에서 깜짝 놀란다. '국민 3명 중 1명이 감염자라고?' 감염이 곧 '결핵'을 의미하는 것은 아니다. 하지만 감염이 된 사람은 언제든 결핵으로 진전될 가능성을 안고 있는, 잠재적 결핵환자이다. 이 페이지에서는 내 몸에 결핵균이 들어왔는지 여부를 확인 할 수 있는 TST, 즉 투베르쿨린 피부검사에 대해 알아보기로 한다.

• Tuberculosis and Respiratory Diseases
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• v.72 no.2
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• pp.140-148
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• 2012

Background: Detection and treatment of tuberculosis (TB) infection with contact investigation is a key component of TB control program. I evaluated the prevalence and risk factors for TB infection among contacts of recently diagnosed pulmonary TB patients in a tertiary hospital in Korea. Methods: 206 contacts of 90 adult pulmonary TB patients underwent tuberculin skin tests (TST) and chest radiography. The TST results were considered positive with an induration of 10 mm or more, suggesting TB infection. A standardized questionnaire was used to assess risk factors associated with TB infection. Results: TST was positive in 97 of 206 contacts of TB patients (47.1%) and positive rate of TST increased with age. The risk of TB infection was significantly associated with close contact with TB patients (sleeping in the same room) (odd ratio [OR], 4.94; 95% confidence interval [CI], 1.43~17.00). Conclusion: TB infection rate was higher in the elderly, and the risk of TB infection was significantly increased with close contact of TB patients.

• Tuberculosis and Respiratory Diseases
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• v.78 no.4
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• pp.349-355
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• 2015

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 $3.9{\pm}0.9years$. 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+ ${\geq}$ 16% (OR, 3.11; 95% CI, 1.29-7.51; area under curve, 0.64). Conclusion: 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.

• The Korean journal of internal medicine
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• v.33 no.6
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• pp.1241-1251
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• 2018

Background/Aims: To estimate the level of agreement and positivity rates of latent tuberculosis infection (LTBI) tests prior to the use of tumor necrosis factor (TNF) inhibitors in relation to underlying rheumatic diseases and endemic tuberculosis levels. Methods: The Ovid-Medline, Embase, and Cochrane Libraries were searched for articles before October 2013 involving LTBI screening in rheumatic patients, including rheumatoid arthritis (RA), ankylosing spondylitis (AS), juvenile idiopathic arthritis (JIA), and psoriatic arthritis. Results: In pooled analyses, 5,224 rheumatic patients had undergone both a tuberculin skin test (TST) and an interferon-gamma release assay (IGRA) before TNF inhibitors use. The positivity of TST, QuantiFERON-TB Gold In Tube (QFT-GIT), and T-SPOT.TB (T-SPOT) tests were estimated to be 29%, 17%, and 18%, respectively. The agreement percentage between the TST and QFT-GIT, and between the TST and T-SPOT were 73% and 75%. Populations from low-to-moderate endemic TB presented with slightly less agreement (71% between TST and QFT-GIT, and 74% between TST and T-SPOT) than patients from high endemic countries (73% between TST and QFT-GIT, and 81% between TST and T-SPOT). By underlying disease stratification, a lower level of agreement between TST and QFT-GIT was found among AS (64%) than among JIA (77%) and RA patients (73%). Conclusions: We reaffirm the current evidence for accuracy of LTBI test done by TST and IGRA among rheumatic patients is inconsistent. Our stratified analysis suggests different screening strategies might be needed in clinical settings considering the endemic status in the patient's country of origin and the precise nature of underlying diseases.

• Journal of Preventive Medicine and Public Health
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• v.52 no.4
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• pp.272-275
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• 2019

The 2018 National Guideline for Tuberculosis Control, which was published by the Korea Centers for Diseases Prevention and Control (KCDC), mandates conducting an epidemiological survey among close contacts of active tuberculosis patients at public institutions such as schools. In the procedure for these surveys, the tuberculin skin test (TST) is mandated as the screening test for latent tuberculosis infection in elementary school students. However, several guidelines recommend using the interferon-gamma releasing assay (IGRA) for contacts aged over 5 years with a Bacillus Calmette-$Gu{\acute{e}}rin$ vaccination history. The main reason for this is that IGRA has a higher specificity and lower false positive rate than TST. In addition, IGRA requires only a single visit to draw blood and the results are available within 24 hours. These advantages could promote cooperation from both parents and students in conducting these surveys. Thus, these findings regarding the benefits of IGRA for surveys of close contacts at elementary schools should be incorporated into the KCDC guideline.

• Tuberculosis and Respiratory Diseases
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• v.68 no.3
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• pp.155-161
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• 2010

Background: The tuberculin skin test (TST) has limitations in diagnosing a latent tuberculosis infection (LTBI). The interferon-gamma release assay (IGRA) was introduced to middle- and high-school students since 2009 by the Korea Centers for Disease Control and Prevention. The aim was to evaluate the utility of IGRA in diagnosing LTBI in middle- and high-school students. Methods: From August 2007 to July 2009, among suspected LTBI students showing TST induration with a 10 mm diameter and over with a normal chest x-ray in school students of Jeju city, 341 students underwent a Quanti FERON-TB Gold In-Tube (QFT-IT) test to confirm LTBI. Results: From 348 students showing a positive TST, a QFT-IT test was carried out on 341 students. The positive QFT-IT rate was 52.8% (=180/341). The positive QFT-IT rate was higher in high-school boys with a 15~19 mm diameter of induration in TST. Conclusion: With the introduction of IGRA for diagnosing LTBI in middle- and high-school students, approximately 47% of students who show a TST induration with a 10 mm diameter and over can avoid taking unnecessary preventive chemotherapy. These results suggest that IGRA is useful for diagnosing and controlling LTBI in Korean students.