Whole blood interferon-gamma assay for baseline tuberculosis screening among Japanese healthcare students

The annual risk of tuberculosis infection in newly hired researchers and healthcare workers using interferon-gamma release assay in Japan

The tuberculosis (TB) notification rate in Japan is gradually decreasing but has not yet achieved "pre-elimination," defined by the World Health Organization. To effectively tackle, control, and eliminate TB, estimating and monitoring the annual risk of TB infection (ARI) using tuberculin skin testing (TST) to understand the dynamics of TB epidemiology are significantly important. However, studies estimating ARIs using TST are few considering that Bacillus Calmette-Guérin vaccination coverage is high in Japan. This was a single-center, cross-sectional study conducted between January 2011 and December 2018 in Tokyo area where interferon-gamma release assays (IGRAs) were performed in newly hired researchers of Keio University School of Medicine and healthcare workers of Keio University Hospital to determine TB infection. We estimated the prevalence of TB infection and ARI based on their IGRA results. Among the 3908 subjects, 83 (2.124%) had positive IGRA results. Multiple logistic regression analysis revealed that age was a significant risk factor for positive IGRA result (adjusted odds ratio, 1.046). The ARIs were 0.049%-0.156% between 1986 and 2004, midyears of TB infection, but have not significantly decreased over approximately two decades. To decrease the risk of TB infection, advanced strategies to control and eliminate TB in Tokyo area are significantly required.

Risk of Occupational Latent Tuberculosis Infection among Health Personnel Measured by Interferon-Gamma Release Assays in Low Incidence Countries-A Systematic Review and Meta-Analysis

Healthcare workers (HCWs) have increased risk for latent tuberculosis infection (LTBI) and tuberculosis (TB) disease due to their occupational exposure. For some years now, interferon-γ release assays (IGRAs) have replaced the tuberculin skin test for the diagnosis of LTBI in many countries. This review examined the occupational risk of LTBI in HCWs with IGRA testing in low incidence countries. A systematic review and meta-analysis of studies from 2005 onwards provide data regarding the prevalence of LTBI in HCWs. In addition, the pooled effect estimates were calculated for individual regions and occupational groups. 57 studies with 31,431 HCWs from four regions and a total of 25 countries were analysed. The prevalence of LTBI varied from 0.9 to 85.5%. The pooled estimation found the lowest prevalence of LTBI for North American and West Pacific countries (<5%), and the highest prevalence for Eastern Mediterranean countries (19.4%). An increased risk for LTBI was found only for administrative employees. Studies on the occupational risk of LTBI continue to show increased prevalence of HCWs, even in low-incidence countries. Good quality studies will continue to be needed to describe occupational exposure.

Unaffected reaction level in tuberculin skin test by long-term therapy with tumor necrosis factor inhibitors for rheumatoid arthritis

AIM

The tuberculin skin test (TST) is used to diagnose tuberculosis; however, the influence of tumor necrosis factor (TNF) inhibitors on the test is unclear. This study investigated whether therapy with TNF inhibitors suppresses the TST reaction due to immunosuppression or whether the TST reaction increases due to reactivation of latent Mycobacterium tuberculosis infection.

METHOD

Ninety-one patients with rheumatoid arthritis receiving TNF inhibitors (40 using infliximab and 51 using etanercept) were studied. The TST was performed before starting TNF inhibitors (T1) and more than 1 year after starting them (T2).

RESULTS

At T1, the reaction was negative in 45 patients, weakly positive in 21 patients, moderately positive in 18 patients and strongly positive in seven patients, while the numbers at T2 were 44, 20, 16 and 11, respectively. There were no significant differences of the TST reaction between T1 and T2 in all patients (P = 0.657), patients using infliximab (P = 0.462) or patients using etanercept (P = 1.00). No patients with a strongly positive TST reaction at T1 became negative at T2. However, two patients who were negative at T1 became strongly positive at T2. Although they had no signs of M. tuberculosis infection, isoniazid prophylaxis was given.

CONCLUSION

The TST reaction was not suppressed after more than 1 year of therapy with TNF inhibitors. Patients in whom the TST reaction changes from negative to strongly positive may need appropriate prophylaxis.

Interferon-γ Release Assay vs. Tuberculin Skin Test for Tuberculosis Screening in Exposed Healthcare Workers: A Longitudinal Multicenter Comparative Study

OBJECTIVE

Healthcare workers (HCWs), especially those caring for patients with tuberculosis (TB), are at high risk of acquiring that disease. The poor specificity of tuberculin skin testing (TST) prompted us to evaluate the effectiveness of the interferon-γ release assay (IGRA) in comparison with TST in a large prospective, multicenter, 1-year study of HCWs with occupational exposure to TB.

METHODS

HCWs from high-risk units at 14 university hospitals were invited to participate and underwent both TST and IGRA (first Quantiferon TB Gold-IT®, QFT-G, then T-SPOT.TB® if QFT-G was indeterminate) at baseline and after 1 year. We collected demographic characteristics, country of birth, history of TB, immunosuppression, past exposure to TB, history of BCG vaccination, results of most recent TST, job category, and duration of current function.

RESULTS

Among 807 HCWs enrolled, current or past TST at baseline was positive (≥15 mm) in 282 (34.9%); the IGRA was positive in 113 (14.0%) and indeterminate in 3 (0.4%). After 1 year, 594 HCWs had both an IGRA and TST (or prior TST≥15 mm) at baseline and an IGRA and TST (if indicated). The conversion rate was 2.5% (9 of 367) with TST and 7.6% (45 of 594) with IGRA, with poor agreement between the 2 tests. Using only QFT-G, conversion (9.9%) and reversion (17.8%) rates were higher for baseline QFT-G positive quantitative values <1 IU/mL.

CONCLUSION

TST and the IGRA yielded discordant results. The value of IGRA in addition to TST remains undetermined; the two should be jointly interpreted in decision-making (clinical trial registration NCT00797836).

Infect Control Hosp Epidemiol 2015;00(0): 1–6

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.

[Usefulness of Quantiferon-TB Gold in Tube® in screening for latent tuberculosis infection in health workers]

INTRODUCTION

Healthcare workers (HW) are considered a risk group for exposure to tuberculosis. Screening for latent tuberculosis infection (LTBI) is mandatory in all HW. The Tuberculin test (TT) has been used up until now for LTBI screening, but gives a high number of false positives, especially in patients vaccinated with BCG. Diagnostic methods based on detection of specific gamma interferon (IGRA) have recently appeared on the market in order to improve these drawbacks, but pose other dilemmas. The aim of this study is to determine the agreement between the two types of test and to carry out a cost-benefit study of the possible diagnostic strategies.

MATERIAL AND METHODS

All newly hired HW by the Hospital Universitari Mútua Terrassa between January 2010 and October 2011 we were included in the study, as well as those who had their occupational review. Workers who been in contact with patients admitted with tuberculosis before the initial isolation were also tested. In all cases a parallel TT and serum QuantiFeron-TB Gold-in-Tube(®) (QF-G-IT) assays were performed. TB disease was ruled out in all professional by chest X-ray. The TT was considered positive when it was equal to or more than 10mm and if the QF-G-IT was 0.35 IU/mL. A cost-effectiveness analysis was designed with three possible strategies to detect LTBI in order to find the one with the best cost-benefit.

RESULTS

A total of 226 HW were studied, with a mean age 30.65 ± 16, of whom 44 (19.4%) had previous BCG vaccination history, and 8 (3.5%) unknown. The TT was positive in 33 (14.6%) cases and the QF-G-IT in 17 (7.5%). The values of the TT and QF-G-IT were both positive in 15 cases. In 18 (8%) The TT was positive in 18 (8%) of cases with a negative QF-G-IT value. The agreement between the two tests was 91%, with a Kappa of 0.55. In vaccinated cases, the correlation was 70.5%, with a Kappa of 0.33, while in unvaccinated it was 98.9% with a Kappa of 0.65. The cheapest screening strategies for LTBI diagnosis were those based on TT, but followed closely by the strategy based on TT with reconfirmation of positives with QF-G-IT.

CONCLUSIONS

QF-G-IT seems to be a very sensitive technique to detect LTBI and allows false positives due to TT to be detected, particularly in BCG vaccinated HW. In this group QF-G-IT could be the ideal test to detect truly infected staff, and avoid unnecessary chemoprophylaxis. The most cost-benefit strategy was those based in TT with reconfirmation or rejection of positive cases by QF-G-IT.

Serial QuantiFERON TB-2G testing over a four-year period in healthcare workers at a city hospital

OBJECTIVE

To evaluate the performance and practicality of QuantiFERON TB-2G (QFT-2G) testing for screening healthcare workers (HCWs) at a city hospital in Japan without a tuberculosis (TB)-specific ward.

METHODS

We performed a chart review of 951 HCWs (251 men and 700 women) who underwent QFT-2G testing as a part of their pre-employment or annual employee screening between April 2007 and March 2010.

RESULTS

The initial QFT-2G test was interpreted as positive in 28 (2.9%) HCWs, negative in 884 HCWs (92.9%) and indeterminate in 39 HCWs (4.1%). During the four-year study period, 37 HCWs were diagnosed as being positive at least once. Nine (0.98%) of the 923 HCWs with indeterminate or negative results on the initial testing converted to a positive status, including 6/479 (1.25%) nurses, 2/100 (2.0%) office staff members and 1/147 (0.68%) physicians. No HCWs with a positive result had a history of tuberculosis (TB) or any apparent contact with active TB patients and did not opt for treatment of latent TB. Seven (25%) of the 28 HCWs who were determined to be positive on the initial testing reverted to an indeterminate or negative status.

CONCLUSION

In a series of annual serial QFT-2G tests, some HCWs exhibited conversion and/or reversion. Therefore, caution is required when interpreting mild fluctuations in interferon-γ responses.

Tuberculosis examination using whole blood interferon-gamma release assay among health care workers in a Japanese hospital without tuberculosis-specific wards

Occupational latent tuberculosis infection (LTBI) among health care workers (HCWs) is an important public health issue. The objective of this study is to assess prevalence and risk factors of LTBI among Japanese HCWs by Quantiferon-TB Gold in Tube (QFT-GIT) and the structured questionnaire. This is a cross-sectional study involving HCWs from a hospital without tuberculosis-specific wards, receiving QFT-GIT for LTBI screening. We reviewed medical records of HCWs and questioned HCWs about exposure to M. tuberculosis and employment length in health care industries. 165 HCWs, approximately 80% of the total hospital staff, were enrolled in this study.18 out of 165 subjects had positive results, suggesting LTBI prevalence rate of 11%. Multiple regression analysis revealed a significant association between the positive or intermediate QFT-GIT results and history of contact investigation for tuberculosis. QFT-GIT positivity rate among HCWs is higher than among general population in Japan.

Performance of interferon-gamma release assays in patients with inflammatory bowel disease: a systematic review and meta-analysis

BACKGROUND

Guidelines mandate screening for latent tuberculosis infection (LTBI) prior to anti-tumor necrosis factor (anti-TNF) therapy in patients with inflammatory bowel disease (IBD). However, many are already on immunosuppressive therapy (IST) that may affect the precision of the Tuberculin skin test (TST). Our aim was to assess the performance of the new interferon-gamma release assays (IGRAs) to detect LTBI in patients with IBD.

METHODS

MEDLINE and EMBASE were searched (up to June 2011) to identify studies evaluating the performance of IGRAs (QuantiFERON-TB Gold [QFT-2G], QuantiFERON-TB Gold In-Tube [QFT-3G] and T-SPOT.TB) in individuals with IBD. Forest plots and pooled estimates using random effects models were created where applicable.

RESULTS

Nine unique studies encompassing 1309 patients with IBD were included for analysis. The pooled concordance between the TST and QFT-2G/QFT-3G was 85% (95% confidence interval [CI] 77%-90%). The concordance of the TST and TSPOT.TB was 72% (95% CI 64%-78%). Studies assessing agreement reported more IGRA-/TST+ results versus IGRA+/TST- results. The pooled percentage of indeterminate results was 5% (95% CI 2%-9%) for QFT-2G/QFT-3G. TSPOT.TB showed similar results. Both positive QFT-2G/QFT-3G results (pooled odds ratio [OR] 0.37, 95% CI 0.16-0.87) and positive TST results (pooled OR 0.28, 95% CI 0.10-0.80) were significantly influenced by IST (both P = 0.02).

CONCLUSIONS

While it remains difficult to determine superiority between the IGRAs and the TST, both are negatively affected by IST. Therefore, screening prior to initiation of IST should be considered. Nevertheless, it is imperative that all patients receive screening prior to anti-TNF therapy.

A statistical method was used for the meta-analysis of tests for latent TB in the absence of a gold standard, combining random-effect and latent-class methods to estimate test accuracy

OBJECTIVE

Because of the lack of a gold standard, the diagnostic performance of tests for the detection of latent tuberculosis infection (LTBI) is not known. However, statistical methods can be used to estimate the accuracy from the studies reporting the concordance among the tests.

STUDY DESIGN AND SETTING

We developed a random-effect latent-class model to estimate performance characteristics of three LTBI diagnostic tests: tuberculin skin test (TST, at 10-mm cutoff), QuantiFERON-TB gold (QFG), and TSPOT-TB from the studies evaluating agreement among the tests.

RESULTS

Nineteen studies were included. QFG had a sensitivity of 0.642 (95% confidence interval [CI]: 0.593-0.691) and specificity of 0.996 (95% CI: 0.989-1.000), TSPOT-TB had a sensitivity of 0.500 (95% CI: 0.334-0.666) and specificity of 0.906 (95% CI: 0.882-0.929), and TST had a sensitivity of 0.709 (95% CI: 0.658-0.761) and specificity of 0.683 (95% CI: 0.522-0.844). Results were not sensitive to the inclusion of any single study. When only the three studies that reported on TSPOT were removed, estimates for the other two tests varied minimally.

CONCLUSIONS

Statistical methods can help estimate the accuracy of LTBI tests. Although the specificities were close to their reported values in the literature, the estimates for sensitivities were low; a finding that should be carefully evaluated.

Role of interferon-gamma release assays in healthcare workers

The advent of interferon-gamma release assays (IGRAs) provides new options for detection of latent tuberculosis infection (LTBI). This is particularly relevant to healthcare workers (HCWs), who are at higher risk of infection, but who have often also been vaccinated. In this article, we discuss the role of IGRAs for the diagnosis of LTBI in various healthcare settings. A search was performed for studies that reported data on IGRAs in HCWs in the last 18 years. Twenty-two studies met the inclusion criteria. IGRAs showed poor agreement with the tuberculin skin test (TST), except in countries with high incidences of tuberculosis (TB), but generally correlated better with markers of exposure to TB including during contact investigation. The T-SPOT.TB assay has not been adequately assessed in HCWs; the few studies available showed enhanced specificity of T-SPOT.TB when compared to TST. This review confirms the utility of IGRAs as important tools in the prevention and control of tuberculosis in healthcare settings.

T-cell interferon-gamma release assays for the rapid immunodiagnosis of tuberculosis: clinical utility in high-burden vs. low-burden settings

PURPOSE OF REVIEW

The utility of T-cell interferon-gamma (IFN-gamma) responses to Mycobacterium tuberculosis specific antigens [interferon-gamma release assays (IGRAs)] in high-burden settings remains unclear and there is growing evidence that IGRA performance varies across high tuberculosis (TB) burden vs. low TB burden settings. Here we review the evidence supporting the utility of IGRAs in specific subgroups and compare their performance in high-burden vs. low-burden settings.

RECENT FINDINGS

Although the IGRA, compared with the tuberculin skin test (TST), has greater specificity in BCG-vaccinated individuals, treatment of latent tuberculosis infection is not a priority in high-burden setting. Nevertheless, in high-burden settings, the TST performs reasonably well and correlates as well, or better, with proxy measures of exposure.

SUMMARY

IGRAs may still be useful in high-burden settings in specific subgroups at high risk of progression, including young children, HIV-infected individuals and healthcare workers, but this requires confirmation. Although the IGRAs cannot distinguish between latent and active TB, their utility as rule-out tests, when combined with smear microscopy or the TST, requires further study. Prospective studies are required in high-burden settings to confirm whether IFN-gamma responses are predictive of high risk of progression to active TB, particularly in HIV-infected individuals.

Evaluation of a model for efficient screening of tuberculosis contact subjects

RATIONALE

Contact tracing is an important component of tuberculosis (TB) control programs. Standardization of contact investigation protocols can make them more efficient.

OBJECTIVES

To develop a model to select contact subjects for screening.

METHODS

We prospectively collected standardized data on 325 TB index cases and their 2,009 contacts. Factors that independently influenced the risk of TB infection were included in the model, which was then validated in a second prospective cohort of 88 cases of TB and their 618 contacts.

MEASUREMENTS AND MAIN RESULTS

A total of eight independent risk factors were identified (odds ratio; 95% confidence interval): age, with three subgroups: 6-14 years (3.6; 1.6-8.0); 15-29 years (3.7; 1.8-7.7); > or =30 years (4.1; 2.0-8.5); cavitation on the index case's chest radiograph (1.6; 1.1-2.2); an index case sputum smear with 100 or more acid-fast bacilli per field (1.8; 1.2-2.8); household contact at night (2.1; 1.3-3.2); first-degree family relationship with the index case (2.1; 1.3-3.3); active smoking by the contact (1.6; 1.1-2.4); free health care (2.0; 1.2-3.2); and birth in a country with TB incidence rate higher than 25 of 100,000 (2.2; 1.5-3.2). Predictive probabilities were chosen to ensure false-negative rates lower than estimated TB infection background. The number of contacts to be investigated was reduced by 26% while maintaining a false-negative rate of 8%.

CONCLUSIONS

This study provides a standardized contact screening model which reduces resources required without negatively affecting disease control.