• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.30 no.1
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• pp.67-74
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• 2020

Objectives: Previous study has shown that the positive rate of latent tuberculosis infection(LTBI) among former workers in dusty environments was higher than that among high-risk groups of tuberculosis(TB). The objective of the present study was to identify the development of active TB among former workers in dusty environments diagnosed with LTBI. Methods: Between January 2015 and May 2017, 796 former workers in dusty environments who had been subjects of epidemiology research for work-related chronic obstructive pulmonary disease(COPD) had received the QuantiFERON-TB® Gold In-Tube(QFT-GIT) from the Institute of Occupation and Environment(IOE) under the Korea Workers' Compensation and Welfare Service(KCOMWEL). Among them, 437 participants who received a health examination for work-related pneumoconiosis between January 2015 and December 2018 were selected as study subjects. Active TB was defined as a positive result for active PTB and non-tuberculosis mycobacteria infection in the result of the Pneumoconiosis Examination Council's assessment by KCOMWEL. Results: A total of 437 subjects were followed up for 2.1 years. Four of them(4/437, 0.9%) developed active TB during the follow-up period. The attack rate of active TB among subjects who were diagnosed LTBI positive and those who were diagnosed LTBI negative were 0.9%(3/320) and 0.9%(1/115), respectively. Conclusions: Most previous studies reported that the attack rate of the development of active TB in subjects who had been diagnosed LTBI positive was higher than that among subjects who had been diagnosed LTBI negative. To the contrary, the present study found that the rate of developing active TB among former workers in dusty environments diagnosed as LTBI positive was not higher than that in those who were diagnosed LTBI negative.

• Tuberculosis and Respiratory Diseases
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• v.73 no.4
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• pp.219-223
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• 2012

Background: We investigated the prevalence of latent tuberculosis infection (LTBI) among medical students in South Korea. Methods: Students from one medical school, who were in second- or third-year classes before clerkship course, were enrolled for three consecutive years in the study. A standard questionnaire was given to each participant, and tuberculin skin test (TST), QuantiFERON-TB GOLD In-Tube (QFT-GIT) assay, and chest radiography were performed. Results: A total of 153 participants were enrolled in the study. The mean age of the subjects was $21.9{\pm}0.9$ years, 105 (68.6%) were male, and 132 (86.3%) had been vaccinated with Bacille Calmette-Gu$\acute{e}$rin (BCG). Four students (2.6%) had a history of contact with tuberculosis (TB) patients during medical practice. No abnormal chest radiograph findings were found for any of the subjects. Of the 153 subjects, 23 (15.0%) tested positive for the TST, and 8 (5.2%) tested positive for the QFT-GIT. The agreement between the two tests was determined to be 0.34 using kappa coefficients. Of the four students who had a history of contact with TB patients, only one subject tested positive for both tests, and the other three students tested negative for both tests. Conclusion: A low prevalence of LTBI was found among medical students before clerkship course in South Korea.

• Tuberculosis and Respiratory Diseases
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• v.81 no.1
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• pp.6-12
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• 2018

The role of the treatment for latent tuberculosis infection (LTBI) has been underscored in the intermediate tuberculosis (TB) burden countries like South Korea. LTBI treatment is recommended only for patients at risk for progression to active TB-those with frequent exposure to active TB cases, and those with clinical risk factors (e.g., immunocompromised patients). Recently revised National Institute for Health and Care Excellence (NICE) guideline recommended that close contacts of individuals with active pulmonary or laryngeal TB, aged between 18 and 65 years, should undergo LTBI treatment. Various regimens for LTBI treatment were recommended in NICE, World Health Organization (WHO), and Centers for Disease Control and Prevention guidelines, and superiority of one recommended regimen over another was not yet established. Traditional 6 to 9 months of isoniazid (6H or 9H) regimen has an advantage of the most abundant evidence for clinical efficacy-60%-90% of estimated protective effect. However, 6H or 9H regimen is related with hepatotoxicity and low compliance. Four months of rifampin regimen is characterized by less hepatotoxicity and better compliance than 9H, but has few evidence of clinical efficacy. Three months of isoniazid plus rifampin was proved equivalence with 6H or 9H regimen in terms of efficacy and safety, which was recommended in NICE and WHO guidelines. The clinical efficacy of isoniazid plus rifapentine once-weekly regimen for 3 months was demonstrated recently, which is not yet introduced into South Korea.

• Tuberculosis and Respiratory Diseases
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• v.81 no.4
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• pp.274-280
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• 2018

Background: The risk of tuberculosis (TB) infection among health care workers (HCWs) is higher than as noted among workers in the general population. The prevalence and risk factors of TB infection among HCWs were assessed in a tertiary hospital in South Korea, resulting in a conclusion of an intermediate TB burden within the country. Methods: This cross-sectional study enrolled HCWs who underwent a QuantiFERON-TB Gold In-Tube (QFT-GIT) test to detect the presence of a latent TB infection (LTBI), in patients admitted to a tertiary hospital in South Korea in 2017. The departments of the hospital were divided into TB-related and TB-unrelated departments, which were based on the risk of exposure to TB patients. In this sense, the risk factors for LTBI, including current working in the TB-related departments, were analyzed. Results: In this case, a total of 499 HCWs (54 doctors, 365 nurses and 80 paramedical personnel) were enrolled in this study. The median age of the subjects was 31 years (range, 20-67 years), 428 (85.8%) were female, and 208 (41.7%) were working in the TB-related departments. The prevalence of LTBI was 15.8% based on the QFT-GIT. Additionally, the prevalence of experience of exposure to pre-treatment TB patents was higher among HCWs working in the TB-related departments, than among HCWs working in the TB-unrelated departments (78.8% vs. 61.9%, p<0.001). However, there was no significant difference in the prevalence of LTBI between the two groups (17.3% vs. 14.8%, p=0.458). On a review of the multivariate analysis, only the factor of age was independently associated with an increased risk of LTBI (p=0.006). Conclusion: Broadly speaking, the factor of age was associated with an increased risk of LTBI among the HCWs in South Korea. However, those workers current working in the TB-related departments was not associated with an increased risk of LTBI.

• 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.

• Health Policy and Management
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• v.23 no.4
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• pp.349-357
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• 2013

Background: Although interferon-gamma release assay (IGRA) is now available alternatives to tuberculin skin test (TST) for detection of latent tuberculosis infection (LTBI), the cost of IGRA test is much higher than TST. So economic analysis of LTBI screening strategies have been done in many countries, but there are few reports in Korea. This study examined cost analysis of LTBI screening strategies in Korea. Methods: The economic outcomes were evaluated by five strategies. These were 1) TST alone, 2) IGRA alone, 3) combination of TST and IGRA (TST followed by IGRA) and 4) no testing no prevention, 5) no testing all prevention. Last two strategies were added to compare with three main LTBI screening strategies. Decision analysis model were used to perform economic analysis. A cohort study of Korean Institute of Tuberculosis and the data of published literatures were used to estimate the cost analysis. Results: In a base-case scenario which was assumed that TST specificity was 80%, TST alone was the least expensive strategy. In a alternative scenario which was assumed that TST specificity was 97%, the combination of TST and IGRA was the least expensive strategy. Sensitivity analysis shows that patients adherent rate to LTBI treatment, TST sensitivity, IGRA sensitivity and IGRA specificity did not have a significant impact on the outcomes. Conclusion: In Korea, for the diagnosis of LTBI at the time of child and adolescent, TST alone reduces medical costs compared with IGRA alone or combination of TST and IGRA.

• Journal of applied mathematics & informatics
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• v.29 no.5_6
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• pp.1097-1115
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• 2011

We consider the global stability of a general tuberculosis model with two differential infectivity, n classes of latent individuals and mass action incidence. This system exhibits the traditional threshold behavior. There is always a globally asymptotically stable equilibrium state. Depending on the value of the basic reproduction ratio $\mathcal{R}_0$, this state can be either endemic ($\mathcal{R}_0$ > 1), or infection-free ($\mathcal{R}_0{\leq}1$). The global stability of this model is derived through the use of Lyapunov stability theory and LaSalle's invariant set theorem. Both the analytical results and numerical simulations suggest that patients should be strongly encouraged to complete their treatment and sputum examination.

• Clinical and Experimental Pediatrics
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• v.59 no.6
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• pp.256-261
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• 2016

Purpose: Latent tuberculosis infection (LTBI) in young children may progress to severe active tuberculosis (TB) disease and serve as a reservoir for future transmission of TB disease. There are limited data on interferon-${\gamma}$ release assay (IGRA) performance in young children, which our research aims to address by investigating the usefulness of IGRA for the diagnosis of LTBI. Methods: We performed a tuberculin skin test (TST) and IGRA on children who were younger than 18 years and were admitted to Chung-Ang University Hospital during May 2011-June 2015. Blood samples for IGRA were collected, processed, and interpreted according to manufacturer protocol. Results: Among 149 children, 31 (20.8%) and 10 (6.7%) were diagnosed with LTBI and active pulmonary TB, respectively. In subjects lacking contact history with active TB patients, TST and IGRA results were positive in 41.4% (29 of 70) and 12.9% (9 of 70) subjects, respectively. The agreement (kappa) of TST and IGRA was 0.123. The control group, consisting of non-TB-infected subjects, showed no correlation between age and changes in interferon-${\gamma}$ concentration after nil antigen, TB-specific antigen, or mitogen stimulation in IGRAs (P=0.384, P=0.176, and P=0.077, respectively). In serial IGRAs, interferon-${\gamma}$ response to TB antigen increased in IGRA-positive LTBI subjects, but did not change considerably in initially IGRA-negative LTBI or control subjects. Conclusion: The lack of decrease in interferon-${\gamma}$ response in young children indicates that IGRA could be considered for this age group. Serial IGRA tests might accurately diagnose LTBI in children lacking contact history with active TB patients.

• 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.

• Clinical and Experimental Pediatrics
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• v.52 no.5
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• pp.513-518
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• 2009

In childhood tuberculosis, it is possible to clearly distinguish among three basic stages: exposure, infection, and disease. The incidence of tuberculosis in children is low compared with that in adults, but latent infection is a major concern because children, who are exposed to Mycobacterium tuberculosis especially early in childhood, are at increased risk of developing the disease. Younger children particularly infants have a high relative risk of miliary or meningeal disease. The clinical manifestations of childhood tuberculosis differ noticeably from those of the disease seen in adults. Adolescents with tuberculosis have different demographic and clinical features from those of adults or children. Tuberculosis in adolescents has become relatively more important as the incidence of infection in childhood has decreased.