Annual incidence of latent tuberculosis infection among newly employed nurses at a tertiary care university hospital

Estimating the burden of nosocomial exposure to tuberculosis in South Korea, a nationwide population based cross-sectional study

BACKGROUND/AIMS

The aim of the study was to investigate the current nationwide burden of nosocomial exposure to tuberculosis (TB) using national health insurance claims data.

METHODS

All patients who had claims for drug susceptibility testing for TB from 2012 to 2016, which indicated culture-proven TB, were included. The first day of the infectious period was defined as 3 months before a doctor's suspicion of TB in patients with respiratory symptoms and 1 month before in patients without symptoms. The last day of the infectious period was defined as one day before the prescription of anti-TB medications. Patients hospitalized during infectious periods were investigated and their hospitalization days were calculated. Records of medical procedures which increased the risk of nosocomial transmission by generating aerosols were also investigated.

RESULTS

A total of 7,186 cases with 94,636 person-days of hospitalization with unrecognized active TB were found. Patients above 60 years of age accounted for 63.99% of the total number and 69.70% of the total duration of hospitalization. TB patients in the older age group showed a trend toward higher risks for hospitalization with unrecognized active TB. Patients in their 80s showed the highest risk (12.65%). Bronchoscopy (28.86%), nebulizer therapy (28.48%), and endotracheal intubation (13.02%) were common procedures performed in these patients during hospitalization.

CONCLUSION

The burden of nosocomial exposure to TB in South Korea is still substantial. Hospitalization with unrecognized active TB, especially among the elderly TB patients could be a serious public health issue in South Korea.

Prevalence of Latent Tuberculosis Infection in the Middle East and North Africa: A Systematic Review

Objective

Data on the prevalence of latent tuberculosis infection (LTBI) in Middle Eastern and North African countries are scarce. We aimed to review all relevant published data in countries belonging to this region to determine the overall prevalence of LTBI in the Middle East and North Africa (MENA) region.

Methods

In this systematic review PubMed and Google Scholar databases were searched for observational, prospective, retrospective, cross-sectional, and cohort studies providing prevalence data of LTBI in any MENA country. Studies fulfilling the search criteria were incorporated in the review. Overall prevalence of LTBI with 95% confidence intervals (CI) was calculated using the random-effects model; heterogeneity was assessed using I² statistics. Gender and age group-based subgroup analyses were performed to evaluate the basis of heterogeneity.

Results

The total number of overall LTBI studies identified was 956, of which 31 studies from ten countries within the MENA region were included that represented 12,439 subjects. The overall prevalence was 41.78% (95% CI 31.18% to 52.78%, I² = 99.31%). By gender-based subgroup analysis, the prevalence of LTBI was 33.12% (95% CI 18.97% to 49.04%, I² = 99.25%) and 32.65% (95% CI 19.79% to 47%, I² = 98.89%) in males and females, respectively, while in the age-based subgroup analysis, the prevalence of LTBI was 0.44% (95% CI -0.05% to 0.9%), 3.37% (95% CI 2.23% to 4.74%, I² = 0%), and 43.81% (95% CI 33.09% to 54.82%, I² = 99.18%) for children, adolescents, and adults, respectively.

Conclusion

This systematic review reveals a high prevalence of LTBI in the MENA region; enhanced LTBI surveillance and prompt infection prevention steps are urgently needed to prevent active tuberculosis, this would help achieve the World Health Organization End TB Strategy 2035, and the United Nations Sustainable Development Goals 2030 target in the MENA region.

Aggressive Contact Investigation of In-Hospital Exposure to Active Pulmonary Tuberculosis

BACKGROUND

In-hospital detection of newly diagnosed active pulmonary tuberculosis (TB) is important for prevention of potential outbreaks. Here, we report our experience of the aggressive contact investigation strategy in a university hospital in the Republic of Korea after healthcare workers (HCWs), patients, and visitors experience an in-hospital exposure to active pulmonary TB.

METHODS

A contact investigation after the unexpected detection of newly diagnosed active pulmonary TB (index patients) was performed in a university hospital from August 2016 to April 2017. Initial and 3-month-post-exposure chest radiographs were advised for all patients, visitors, and HCWs in close contact with the index patients. An additional tuberculous skin test or interferon gamma releasing assay was performed at the time of exposure and 3 months post-exposure in HCWs in close contact with the index patients.

RESULTS

Twenty-four index patients were unexpectedly diagnosed with active pulmonary TB after admission to the hospital with unassociated diseases. The median time from admission to TB diagnosis was 5 days (range, 1-22 days). In total, 1,057 people were investigated because of contact with the index patients, 528 of which had close contact (206 events in 157 HCWs, 322 patients or visitors). Three months post exposure, 9 (9.2%) among 98 TB-naïve close contact HCWs developed latent tuberculosis infections (LTBIs). Among the 65 close contact patients or visitors, there was no radiological or clinical evidence of active pulmonary TB.

CONCLUSION

An aggressive contact investigation after an unexpected in-hospital diagnosis of active pulmonary TB revealed a high incidence of LTBI among TB-naïve HCWs who had contact with the index patients.

Screening and Treatment of Latent Tuberculosis Infection among Healthcare Workers at a Referral Hospital in Korea

Background

Healthcare workers (HCWs) have a high risk of tuberculosis (TB) infection. Since August 2017, Korea has mandated the testing of latent TB infection (LTBI) and recommended treatment from HCWs at medical institutions. However, the acceptance/completion rate and adverse events of LTBI treatment have not been analyzed.

Materials and Methods

From February to August 2017, we conducted a retrospective study at a referral university hospital in Korea, to screen the interferon-gamma release assay (IGRA) tests conducted for all HCWs for detecting and treating LTBI. HCWs diagnosed with LTBI were offered a 9-month isoniazid (9H), 3-month isoniazid/rifampin (3HR), or 4-month rifampin regimen. We investigated the acceptance/completion rate, adverse events, and causes of discontinuation or change in LTBI medication. A major adverse event was one wherein a patient had any adverse event ≥grade 3 causing LTBI treatment interruption.

Results

Of the 1,538 HCWs, 1,379 underwent IGRA testing for LTBI. Among them, 13.6% (187/1,379) tested positive and 73.3% (137/187) received treatment. The overall completion rate was 97.8% (134/137). HCWs were significantly more likely to complete first-line therapy with 3HR than with 9H (91.4% vs. 76.7%, P = 0.02). The most common major adverse event was hepatotoxicity (n = 7), followed by thrombocytopenia (n = 1) and anaphylactic shock (n = 1). Hepatotoxicity and hepatotoxicity (≥ grade 2) were more frequent in 9H than in 3HR (39.5% vs. 17.2%, P = 0.006 and 18.6% vs. 3.7%, P = 0.005, respectively). The median time to hepatotoxicity was 96 days (interquartile range, 20 – 103 days).

Conclusion

Completion of first-line therapy for LTBI is more likely with 3HR than with 9H. This might be related to the development of hepatotoxicity after around 3 months of treatment. Anaphylactic shock and platelet count should be carefully monitored in those receiving rifampin-containing regimens.

The Prevalence and Risk Factors of Latent Tuberculosis Infection among Health Care Workers Working in a Tertiary Hospital in South Korea

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.

In-hospital contact investigation among health care workers after exposure to pulmonary tuberculosis in an intermediate tuberculosis prevalence area: A prospective study

We carried out in-hospital contact investigations of patients with pulmonary tuberculosis and analyzed the prevalence of latent tuberculosis infection (LTBI) among health care workers (HCWs) after TB exposure. A prospective study was conducted of 872 HCWs who were exposed to 55 index cases diagnosed with active pulmonary TB. HCWs after TB exposure were evaluated both TST and chest X-ray at the time of enrollment and 12 weeks after exposure; 625 HCWs (71.6%) underwent both initial assessments; 41 HCWs (6.6%) had a positive TST result. After 12 weeks, 71.1% of HCWs with initial negative TST (n = 415) underwent a second assessment. Ten HCWs had TST conversion. One HCW (0.2%) developed active pulmonary TB. In multivariable analysis, age over 30 years was associated with TST conversion (p = .02). Point prevalence of latent TB was 6.6%, and incidence of LTBI was estimated as 2.4 per 100 HCWs. Strict infection control measures should be emphasized in intermediate TB-burden, BCG-vaccinated countries, especially in HCWs with high risk for TB exposure.

Occupational Risk of Latent Tuberculosis Infection in Health Workers of 14 Military Hospitals

Tuberculosis (TB) is a known occupational risk to health workers. Identifying risk factors in health care settings is critical to the prevention of TB for health workers and patients. In 2014, we carried out a TB screening and survey for 902 health workers from 14 selected military hospitals to determine the prevalence rate of latent tuberculosis infection (LTBI) as well as occupational risk factors. Of all subjects, 19.5% reported having provided TB patient care for 1 year or more (176/902), and 26.9% (243/902) were positive for the tuberculin skin test (TST) (10 mm or more of induration). Additionally, 21.4% (52/243) of those who tested positive were also positive for the interferon-gamma release assay (IGRA). The proportion of LTBI in the study population was 5.8% (52/902). In a multivariate logistic regression analysis, providing TB patient care for one year or more was the only significant occupational risk factor (adjusted odds ratio [aOR], 2.27; 95% confidence interval [CI], 1.13-4.56). This study suggests that military health workers working with TB patients should be regularly examined by chest radiography, TST and IGRA to detect LTBI in the early stage and control nosocomial infection of TB.

Prevalence and risk factors for latent tuberculosis infection among healthcare workers in Nampula Central Hospital, Mozambique

BACKGROUND

Healthcare workers in high tuberculosis burdened countries are occupationally exposed to the tuberculosis disease with uncomplicated and complicated tuberculosis on the increase among them. Most of them acquire Mycobacterium tuberculosis but do not progress to the active disease - latent tuberculosis infection. The objective of this study was to assess the prevalence and risk factors associated with latent tuberculosis infection among healthcare workers in Nampula Central Hospital, Mozambique.

METHODS

This cross-sectional study of healthcare workers was conducted between 2014 and 2015. Participants (n = 209) were administered a questionnaire on demographics and occupational tuberculosis exposure and had a tuberculin skin test administered. Multivariate linear and logistic regression tested for associations between independent variables and dependent outcomes (tuberculin skin test induration and latent tuberculosis infection status).

RESULTS

The prevalence of latent tuberculosis infection was 34.4%. Latent tuberculosis infection was highest in those working for more than eight years (39.3%), those who had no BCG vaccination (39.6%) and were immunocompromised (78.1%). Being immunocompromised was significantly associated with latent tuberculosis infection (OR 5.97 [95% CI 1.89; 18.87]). Positive but non-significant associations occurred with working in the medical domain (OR 1.02 [95% CI 0.17; 6.37]), length of employment > eight years (OR 1.97 [95% CI 0.70; 5.53]) and occupational contact with tuberculosis patients (OR 1.24 [95% CI 0.47; 3.27]).

CONCLUSIONS

Personal and occupational factors were positively associated with latent tuberculosis infection among healthcare workers in Mozambique.

Preventing the Transmission of Tuberculosis in Health Care Settings: Administrative Control

It is well established that health care workers (HCWs) have a considerably higher risk of occupationally acquired tuberculosis (TB). To reduce the transmission of TB to HCWs and patients, TB infection control programs should be implemented in health care settings. The first and most important level of all protection and control programs is administrative control. Its goals are to prevent HCWs, other staff, and patients from being exposed to TB, and to reduce the transmission of infection by ensuring rapid diagnosis and treatment of affected individuals. Administrative control measures recommended by the United States Centers for Disease Control and Prevention and the World Health Organization include prompt identification of people with TB symptoms, isolation of infectious patients, control of the spread of the pathogen, and minimization of time spent in health care facilities. Another key component of measures undertaken is the baseline and serial screening for latent TB infection in HCWs who are at risk of exposure to TB. Although the interferon-gamma release assay has some advantages over the tuberculin skin test, the former has serious limitations, mostly due to its high conversion rate.

Diagnosis and Treatment of Latent Tuberculosis Infection in Healthcare Workers

Tuberculosis (TB) is one of the most important occupational risks for healthcare workers (HCWs) in South Korea. Many policies regarding the control and prevention of TB in healthcare settings recommend that HCWs are tested for latent tuberculosis infection (LTBI) in addition to active TB. Moreover, the Korean Tuberculosis Prevention Act also recommends that HCWs receive regular testing for LTBI. However, there are no specific or detailed guidelines for dealing with LTBI in HCWs. Herein, we discuss the diagnosis and treatment of LTBI in HCWs and focus particularly on the baseline screening of hired HCWs, routine follow-up, and contact investigation.

A prospective cohort study of latent tuberculosis in adult close contacts of active pulmonary tuberculosis patients in Korea

BACKGROUND/AIMS

The objective of this prospective study was to evaluate the diagnosis and treatment of latent tuberculosis infection (LTBI) in adult close contacts of active pulmonary tuberculosis (TB) patients in Korea.

METHODS

Adult close contacts of active pulmonary TB patients were recruited at a regional tertiary hospital in Korea. The participants were tested for LTBI using the tuberculin skin test (TST) and/or QuantiFERON-TB Gold (QFT-G) test. LTBI patients, who consented to treatment, were randomly assigned to receive isoniazid for 9 months (9INH) or rifampin for 4 months (4RIF).

RESULTS

We examined 189 adult close contacts (> 18 years) of 107 active pulmonary TB patients. The TST and QFT-G were positive (≥ 10 mm) in 75/183 (39.7%) and 45/118 (38.1%) tested participants, respectively. Among 88 TST or QFT-G positive LTBI participants, 45 participants were randomly assigned to receive 4RIF (n = 21) or 9INH (n = 24), respectively. The average treatment duration for the 4RIF and 9INH groups was 3.3 ± 1.3 and 6.1 ± 2.7 months, respectively. Treatment was completed in 25 participants (4RIF, n = 16; 9INH, n = 9). LTBI participants who accepted treatment were more likely to be women and have more cavitary lesions on the chest radiographs of index cases and positive TST and QFT-G results compared to those who refused treatment.

CONCLUSIONS

About 40% of adult close contacts of active pulmonary TB patients had LTBI; about 50% of these LTBI participants agreed to treatment.

Predictors of job satisfaction and burnout among tuberculosis management nurses and physicians

OBJECTIVES

This study examined job satisfaction, empowerment, job stress, and burnout among tuberculosis management nurses and physicians in public healthcare institutions.

METHODS

This was a cross-sectional study analyzing survey data collected from 249 nurses and 57 physicians in 105 public health centers, three public tuberculosis hospitals, and one tertiary hospital. The survey questionnaire comprised general characteristics, work-related characteristics, and four index scales (job satisfaction, empowerment, job stress, and burnout). The two-sample t-test was used to estimate the mean differences in the four index scales. Multiple regression analysis was used to determine whether general and work-related characteristics affected the four index scales.

RESULTS

The job satisfaction and empowerment scores of the nurses were lower than those of the physicians. Except for the tuberculosis-specialized hospitals alone, the average job satisfaction scores of nurses were higher than those of physicians. Moreover, the nurses reported more job stress and burnout than did the physicians in tuberculosis departments in public healthcare institutions in Korea; in particular, the burnout reported by nurses was significantly higher than that reported by physicians at the National Medical Center. Marital status, nursing position, number of coworkers, the average number of days of overtime work per month, self-rated health, and hospital type were associated with the four index scales.

CONCLUSIONS

Overall, nurses were more vulnerable to job stress and burnout than physicians. Reducing the workload of nurses by ensuring the presence of sufficient nursing staff and equipment, as well as by equipping facilities to prevent tuberculosis infections, should be considered priorities.

Tuberculin skin test and Quantiferon test agreement and influencing factors in tuberculosis screening of healthcare workers: a systematic review and meta-analysis

Objective

A systematic review and meta-analysis was conducted to evaluate the agreement between Tuberculin Skin Test (TST) and Quantiferon (QFT) in screening for tuberculosis (TB) infection among healthcare workers (HCWs) and to estimate associations between TST and QFT agreement and variables of interest, such as Bacillus Calmette-Guérin (BCG) vaccination and incidence of TB.

Methods

Cross-sectional and longitudinal studies on HCWs, published in English until October 2013, comparing TST and QFT results, were selected. For each study Cohen’s κ value and a 95% confidence interval were calculated. Summary measures and indexes of heterogeneity between studies were calculated.

Results

29 studies were selected comprising a total of 11,434 HCWs. Cohen’s κ for agreement between TST and QFT for 24 of them was 0.28 (95% CI 0.22 to 0.35), with the best value in high TB incidence countries and the lowest rate of BCG vaccination.

Conclusion

Currently, there is no gold standard for TB screening and the most-used diagnostic tools show low agreement. For evidence-based health surveillance in HCWs, occupational physicians need to consider a number of factors influencing screening results, such as TB incidence, vaccination status, age and working seniority.

Tuberculosis before hematopoietic stem cell transplantation in patients with hematologic diseases: report of a single-center experience

Background

Few reports discuss the optimal management of patients diagnosed with tuberculosis (TB) before scheduled stem cell transplantation (SCT), who then proceed with transplantation.

Methods

We found 13 patients with TB before SCT (proven, n = 9; probable, n = 3; possible, n = 1) in the medical records of our institution.

Results

Most of the patients had pulmonary TB (n = 8; disseminated, n = 2; extrapulmonary, n = 3). Eight of 9 patients with proven disease had SCT after at least 100 days of anti-tuberculous medication, ranging from 103 to 450 days. None of those patients suffered TB-related events after SCT. However, 1 patient with proven pulmonary TB who underwent SCT after only 40 days of anti-tuberculous therapy subsequently died of TB meningitis. Patients with possible and probable disease had their transplants after 6–176 days of anti-tuberculous medication, and all were alive at the time of analysis. The entire duration of anti-tuberculous medication was 12 months in most cases. With a follow-up duration ranging from 0.7 to 87.5 months, 4 patients died, but TB was the cause of death in only 1 case.

Conclusion

In conclusion, for proven cases of TB, SCT after >100 days of anti-tuberculous medication is probably feasible and safe, in terms of TB control, in patients with various hematologic diseases.

Gamma interferon release assays for detection of Mycobacterium tuberculosis infection

Identification and treatment of latent tuberculosis infection (LTBI) can substantially reduce the risk of developing active disease. However, there is no diagnostic gold standard for LTBI. Two tests are available for identification of LTBI: the tuberculin skin test (TST) and the gamma interferon (IFN-γ) release assay (IGRA). Evidence suggests that both TST and IGRA are acceptable but imperfect tests. They represent indirect markers of Mycobacterium tuberculosis exposure and indicate a cellular immune response to M. tuberculosis. Neither test can accurately differentiate between LTBI and active TB, distinguish reactivation from reinfection, or resolve the various stages within the spectrum of M. tuberculosis infection. Both TST and IGRA have reduced sensitivity in immunocompromised patients and have low predictive value for progression to active TB. To maximize the positive predictive value of existing tests, LTBI screening should be reserved for those who are at sufficiently high risk of progressing to disease. Such high-risk individuals may be identifiable by using multivariable risk prediction models that incorporate test results with risk factors and using serial testing to resolve underlying phenotypes. In the longer term, basic research is necessary to identify highly predictive biomarkers.

Latent tuberculosis infection in healthcare workers at a community hospital in Qatar

Routine screening of latent tuberculosis infection (LTBI) is recommended as an essential component in the prevention of TB transmission in healthcare facilities.

OBJECTIVE

To determine the prevalence of LTBI among healthcare workers (HCWs) in a community hospital.

METHODS

A descriptive study was carried out at The Cuban Hospital from August 2012 to May 2013 for newly hired medical staff. As part of the preemployment evaluation, the tuberculin skin test (TST) and QuantiFERON-TB Gold In-Tube test (QFT-G) were performed. The information regarding the demographics, profile, experience as HCWs, any previous contact with TB patients and travels abroad were collected.

ANALYSIS

Test of independence, Student's t test and Wilcoxon Mann-Whitney were used. For hypothesis testing, a significance level of 0.05 was adopted.

RESULTS

TST results were positive in 14 subjects (6.9%), of which 11 were nurses, and 12 were females. QFT-G results were positive in six subjects (3.0%), who were older than those with negative results (44.5 vs. 38.9 years) and had more experience as HCW (21.7 vs. 16.8 years). Compared with subjects negative for QFT-G, positive subjects reported a higher frequency of both direct contact with tuberculosis patients (83.3% vs. 25%) and previous travels to countries with high TB incidence.

CONCLUSION

Incidence of LTBI was low, especially when QFT-G results were considered, highlighting the history of traveling to countries with high TB incidence as an associated key factor.

Prevalence of Latent Tuberculosis Infection among Health Care Workers in South Korea: A Multicenter Study

BACKGROUND

We investigated the prevalence of latent tuberculosis infection (LTBI) among the health care workers (HCWs) and analyzed its risk factors in South Korea.

METHODS

A standard questionnaire regarding the baseline demographics and risk factors for LTBI 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 493 participants, 152 (30.8%) doctors and 341 (69.2%) nurses were enrolled in eight tertiary referral hospitals. The mean age of the subjects was 30.6 years old, and 383 (77.7%) were female. Of the 152 doctors, 63 (41.4%) and 36 (23.7%) were positive by TST and by QTF-GIT, respectively, and among the 341 nurses, 119 (34.9%) and 49 (14.4%) had positive TST and QFT-GIT results, respectively. Overall, the agreement between the two tests was 0.22 by the chance corrected proportional agreement rate (kappa coefficient) in 493 subjects. Experience of working in tuberculosis (TB)-related departments was significantly associated with positive LTBI test results by QFT-GIT assay, not by TST. In multivariate analysis, only age was independently associated with increased risk of a positive TST result, while age and experience of working in TB-related departments (odds ratio, 2.29; 95% confidence interval, 1.01-5.12) were independently associated with increased risk of a positive QFT-GIT result.

CONCLUSION

A high prevalence of LTBI was found among South Korean HCWs. Considering the association between the experience of working in TB-related departments and high risk of LTBI, QFT-GIT may be a better diagnostic test for LTBI than TST in HCWs.

Tuberculin skin test and boosted reactions among newly employed healthcare workers: an observational study

Objective

To evaluate the prevalence of and factors associated with latent tuberculosis infection (LTBI) based on the tuberculin skin test (TST) and to estimate the boosted reaction rate among newly employed healthcare workers (HCWs).

Design

Newly employed HCWs between January 2010 and July 2012 at Severance Hospital in South Korea were enrolled in this study. A one-step TST was conducted before October 2011, and a two-step TST after October 2011.

Results

Of 2132 participants, 778 (36.5%) had positive TST results. Being older (odds ratio [OR] 1.10, 95% confidence interval [CI] 1.06–1.13, P<0.001), male (OR 1.78, 95% CI 1.21–2.62, P = 0.003), rejoining the hospital workforce (OR 1.58, 95% CI 1.04–2.40, P = 0.032), and having a previous history of tuberculosis (TB) (OR 18.21, 95% CI 2.15–154.10, P = 0.008) during the one-step period, and being older (OR 1.15, 95% CI 1.10–1.21, P<0.001) during the two-step period were significantly associated with a positive TST. A two-step TST was performed in 556 HCWs, and a boosted reaction was observed in 79 (14.2%). The induration size on the first TST (5–9-mm group) was the only factor associated with a boosted reaction on the second TST.

Conclusions

The prevalence of LTBI based on the TST among newly employed HCWs was high. The boosted reaction rate on two-step TST was not low; therefore, the use of two-step TST may be necessary for regular monitoring in countries with an intermediate TB burden and a high rate of Bacillus Calmette-Guérin vaccination.

Monthly follow-ups of interferon-γ release assays among health-care workers in contact with patients with TB

BACKGROUND

Interferon-γ (IFN-γ) release assays (IGRAs), which can overcome several limitations of the tuberculin skin test in detecting latent TB infection, were introduced recently in routine clinical practice. However, IGRAs are highly dynamic tests, and the T-cell responses tend to fluctuate over time. We wanted to evaluate the conversion and reversion rates of monthly IGRAs over 1 year among health-care workers (HCWs) in contact with patients with TB in South Korea, a country with an intermediate TB burden.

METHODS

Forty-nine HCWs in contact with patients with active pulmonary TB were prospectively enrolled. Interviews on exposure to patients with active TB, a physical examination, and a QuantiFERON TB Gold In-Tube assay (QFT-GIT) were carried out monthly for 1 year.

RESULTS

Among 48 participants, 25 (52%) showed inconsistent results in serial testing. When an increase from< 0.35 IU/mL to ≥ 0.70 IU/mL was applied as the definition of a conversion, inconsistent IGRA results were identified in 13 participants (27.0%). Consistency in QFT-GIT results was associated with age, length of service, and baseline IFN-γ levels, but not with the profession of the participant, degree of TB exposure, or wearing of an N95 mask. In five participants, fluctuations in IFN-γ levels showed levels > 0.70 IU/mL two or more times.

CONCLUSIONS

Fluctuation in IGRA findings was common when HCWs in contact with patients with TB were tested monthly. This could be a result of poor reproducibility of the assay, repeated infection and true reversion, or periodic secretion of antigens from Mycobacterium tuberculosis.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01121068; URL: www.clinicaltrials.gov

Prevalence of Latent Tuberculosis Infection among Medical Students in South Korea

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±0.9 years, 105 (68.6%) were male, and 132 (86.3%) had been vaccinated with Bacille Calmette-Guerin (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.

Conversion rates of an interferon-γ release assay and the tuberculin skin test in the serial monitoring of healthcare workers

PURPOSE

Regular monitoring of latent tuberculosis (TB) infection in healthcare workers (HCWs) is recommended, but the view about the effective method and performance of serial monitoring is controversial. The aim of this study was to determine differences in conversion rates according to TB exposure risk using the tuberculin skin test (TST) and the QuantiFERON-TB Gold In-Tube (QFT-GIT), and to evaluate the reproducibility and within-subject variability of the QFT-GIT in South Korea.

METHODS

Fifty-three HCWs were grouped according to their risk for TB exposure: group 1, high risk (n = 21); group 2, low risk (n = 32). Baseline and follow-up TSTs and QFT-GITs were performed from June 2009 to July 2011. Enzyme-linked immunosorbent assays (ELISAs) were repeated for the second QFT-GIT and a third QFT-GIT was performed after 8 weeks when discordant results of the second TST and QFT-GIT or a conversion or reversion were observed.

RESULTS

No difference in the QFT-GIT conversion rate was evident between the two groups (15.4 vs. 6.5 %, p = 0.57), and no TST conversion was observed. The rate of QFT-GIT positivity was higher in the high-risk group (first QFT-GIT: 38.1 vs. 3.1 %, p = 0.002; second QFT-GIT: 33.3 vs. 9.4 %, p = 0.039). The re-test reproducibility of QFT-GIT results was high (100 %), and the within-subject results of repetitive QFT-GITs were variable.

CONCLUSIONS

Stricter prevention strategies remain necessary in HCWs at high risk of TB exposure, and serial interferon-γ release assays (IGRAs) should be interpreted with caution in HCWs.

Test variability of the QuantiFERON-TB gold in-tube assay in clinical practice

RATIONALE

Although IFN-γ release assays (IGRAs) are widely used to screen for Mycobacterium tuberculosis infection in high-income countries, published data on repeatability are limited.

OBJECTIVES

To determine IGRA repeatability.

METHODS

The study population included consecutive patients referred to The Methodist Hospital (Houston, TX) between August 1, 2010 and July 31, 2011 for latent tuberculosis (TB) infection screening with an IGRA (QuantiFERON-TB Gold In-Tube; Cellestis, Carnegie, Australia). We performed multiple IGRA tests using leftover stimulated plasma according to a prospectively formulated quality control protocol. We analyzed agreement in interpretation of test results classified according to manufacturer-recommended criteria and repeatability of quantitative TB response.

MEASUREMENTS AND MAIN RESULTS

During the study period, 1,086 test results were obtained from 543 subjects. Per the manufacturer's cut-point, the result of the second test was discordant from that of the first in 28 (8%) of 366 patients with valid test results, including 13 with an initial negative result and 15 with an initial positive result. Although agreement between repeat test results was high (κ = 0.84; 95% confidence interval, 0.79-0.90), the normal expected range of within-subject variability in TB response on retesting included differences of ± 0.60 IU/ml for all individuals (coefficient of variation, 14%), and ± 0.24 IU/ml (coefficient of variation, 27%) for individuals whose initial TB response was between 0.25 and 0.80 IU/ml.

CONCLUSIONS

There is substantial variability in TB response when IGRAs are repeated using the same patient sample. IGRA results should be interpreted cautiously when TB response is near interpretation cut-points.

Interferon-gamma release assays for the tuberculosis serial testing of health care workers: a systematic review

BACKGROUND

Interferon-gamma release assays (IGRAs) are increasingly used in the tuberculosis (TB) screening of health care workers (HCWs). However, comparatively high rates of conversions and reversion as well as growing evidence of substantial within-subject variability of interferon-gamma responses complicate their interpretation in the serial testing of HCWs.

METHODS

We conducted a systematic review on the repeat use of the two commercial IGRAs, the QuantiFERON-TB Gold or In-Tube version (QFT) and the T-SPOT.TB (T-SPOT), in the serial testing and its with-subject variability among HCWs in order to provide guidance on how to interpret serial testing results in the context of the periodic screening of subjects with an increased occupational risk of latent TB infection (LTBI) in countries with low and intermediate TB incidence rates. The Medline, Embase, and Cochrane databases were searched without restrictions. Retrieved articles were complemented by additional hand searched records. Only studies that used commercial IGRAs among HCWs apart from contact and outbreak investigations and those fulfilling further predefined criteria were included.

RESULTS

Overall, 20 studies, five using the T-SPOT and 19 using the QFT assay, were included. Fifteen studies met eligibility criteria for serial testing and five studies for within-subject variability. Irrespective of TB incidence rates in the study's country of origin, reversion rates were consistently higher than conversion rates (range 22-71% vs. 1-14%). Subjects with baseline results around the diagnostic threshold were more likely to show inconsistent results on retesting. The within-subject variability of interferon-gamma responses was considerable across all studies systematically assessing it.

CONCLUSIONS

On the basis of reviewed studies we advocate using a borderline zone from 0.2-0.7 IU/ml for the interpretation of repeat QFT results in the routine screening of HCWs with an increased LTBI risk. Subjects with QFT results within this borderline zone, with suspected fresh infection, and those who are considered for preventive chemotherapy should be retested with the QFT within a period of about four weeks before preventive chemotherapy is recommended. However, the available data regarding the use of the T-SPOT in the serial testing of HCWs is remarkably limited and warrants further research.

Latent tuberculosis infection screening for laboratory personnel using interferon-γ release assay and tuberculin skin test in Korea: an intermediate incidence setting

BACKGROUND

Though recent reports have indicated a higher prevalence of latent tuberculosis infection (LTBI) in laboratory personnel than in other healthcare workers, these studies included only a limited number of laboratory personnel.

METHODS

We have thus focused on the laboratory personnel, who had a high level of exposure to specimens from patients with TB. We recruited 173 laboratory personnel and performed QuantiFERON-TB Gold In-Tube test (QFT-G) and tuberculin skin test (TST).

RESULTS

QFT-G was positive in 21.4% of the enrolled laboratory personnel, and TST was positive in 33.3%. The agreement between the two tests was fair (κ = 0.234). In multivariate analyses, household contactwith TBpatients (P = 0.013), the laboratory sections of microbiology (P = 0.045) and chemistry/immunology (P = 0.014) were shown to be significantly associated with positive QFT-G results.

CONCLUSION

Our data show a high prevalence of TST and QFT-G positivity in laboratory personnel and emphasize the importance of LTBI screening for laboratory personnel. In BCG-vaccinated populations with an intermediate incidence setting, QFT-G seems to be superior to TST as a screening tool for the detection of LTBI. Further study, including results of follow-up tests will be helpful for confirmation of our findings.

Within-subject variability of Mycobacterium tuberculosis-specific gamma interferon responses in German health care workers

Gamma interferon (IFN-γ) release assays (IGRAs) are used increasingly for the periodic tuberculosis (TB) screening of health care workers (HCWs), although data regarding the reproducibility and interpretation of serial testing results in countries with a low incidence of TB are scarce. The present study evaluated and compared the within-subject variability of dichotomous and continuous results of two commercial IGRAs, the QuantiFERON-TB Gold In-Tube (QFT) and the T-SPOT.TB (T-SPOT), in German HCWs during a 4-week period. Thirty-five immunocompetent HCWs with low or medium TB screening risk and without known recent TB exposure or tuberculin skin test application were tested repeatedly with both IGRAs at weekly intervals. A total of 158 valid results were obtained for each IGRA. Changes of about ±70% (QFT) and ±60% (T-SPOT) from the mean IFN-γ response accounted for 95% of the within-subject variability. However, according to the manufacturers' cutoffs, inconsistent results were observed more frequently for the QFT (28.6%; four conversions, six reversions) than for the T-SPOT (8.6%; three reversions; P < 0.001). The overall agreement between the IGRAs was good. Regression toward the means accounted for a significant decline in mean IFN-γ responses of about 25% between successive visits for both IGRAs. Although both assays were highly reliable and reproducible, we observed substantial within-subject variability and regression toward the means during a 4-week period, which should be considered when interpreting serial testing results in comparable populations and settings. Our data support the use of borderline zones for the interpretation of serial IGRA results and the retesting of borderline positive results before offering preventive chemotherapy.

Screening for latent tuberculosis infection in South Korean healthcare workers using a tuberculin skin test and whole blood interferon-gamma assay

This study compared the results of a tuberculin skin test (TST) and a whole-blood interferon-gamma release assay (IGRA) to screen latent tuberculosis (TB) infection (LTBI) according to risk of TB exposure in South Korea. A cross-sectional comparison of 82 healthcare workers (HCWs) was performed from June 2009 to January 2010. Participants were grouped according to their risk for TB exposure: group 1, frequent and direct contact with active TB patients (n = 35); group 2, no known history of direct contact with active TB patients (n = 47). For the TST (10-mm induration cut-off), the positive response rate was 42.9% in group 1 and 34.0% in group 2 (p = 0.42). For the IGRA, the positive response rate was 40% in group 1 and 10.6% in group 2 (p = 0.002). Results obtained from the TST and the IGRA were not in significant agreement. The working duration of HCWs in TB-related departments was the only significant risk factor for LTBI (odds ratio 1.03; p = 0.031). Further, the IGRA can more accurately discriminate LTBI compared to the TST, based on the risk of TB exposure. These results suggest that the IGRA is diagnostically useful for LTBI in South Korean HCWs.

Occupational infection in Korea

Occupational infection is a human disease caused by work-associated exposure to microbial agents through human and environmental contact. According to the literature, occupational infection was the third leading cause of occupational disease (861 cases, 8.0%), and health care, agricultural, forestry, and fishery workers were risk groups in Korea. In addition, most high-risk groups have not been protected by workers' compensation, which could lead to underestimation of the exact spectrum and magnitude of the problem, and may also result in a lack of development and implementation of occupational infection management. Through a review of national guidelines and documentations on prevention and control of occupational infection, a management strategy would promote adherence to worker safety regulations if it is explicit with regard to the agent and mode of infection in each of the high-risk groups.

Interferon-γ release assay for tuberculosis screening of healthcare workers at a Korean tertiary hospital

The aim of this study was to evaluate the annual incidence of tuberculosis infection among newly employed doctors and nurses in Korea. The annual incidence of tuberculosis infection ranged from 3.3% to 5.7%, based on the definition of conversion of an interferon-γ release assay, which suggests that stricter preventive strategies against nosocomial TB infection should be employed. Follow-up interferon-γ levels measured after 3 months of isoniazid and rifampicin treatment showed considerable variation. Therefore, serial testing with interferon-γ release assays after treatment of latent TB infection may be insufficient for evaluating the effects of treatment due to the variable responses.