T-SPOT.TBInterferon-γ Release Assay Performance in Healthcare Worker Screening at Nineteen U.S. Hospitals

Safety of a Novel ESAT6-CFP10 skin test compared with tuberculin skin test in a double-blind, randomized, controlled study

Background

ESAT6-CFP10 (EC) skin test has been reported accurate and safe in identifying tuberculosis infection. We aimed to demonstrate the safety of EC skin test compared with tuberculin skin test (TST) in university freshmen.

Methods

We conducted a double-blind, randomized, controlled clinical study in a university freshmen population with 16,680 participates in China, and finally 14,579 completed the study. About a half received an EC skin test and the others received TST. Adverse reactions were evaluated.

Results

Out of the 14,579 participants, 48.2% (7029/14,579) were males. The average age was 18.1 ± 0.8 years and the average BMI was 20.9 ± 3.1 kg/m². 50.4% (7351/14,579) participants received EC skin test and 49.6% (7228/14,579) received TST. The EC group had significantly less adverse reactions compared with the TST group (21.3%, 1565/7351 vs. 34.6%, 2499/7228, P = 0.000). The most common adverse reactions for EC were bleeding (5.63%, 414), dermatodyschroia (4.27%, 314), induration (3.90%, 287), swelling (2.49%, 183), pain (1.59%, 117) and pruritus (1.48%, 109). Bleeding, dermatodyschroia, swelling and erythema were significantly less in EC group (P < 0.05), while others were similar to those of TST.

Conclusion

the EC skin test was safe in our cohort. And its incidence of total adverse drug reactions (ADRs) is less than that of TST. Most adverse reactions were mild or moderate, lasting less than 48 h and self-limiting. Considering the satisfactory diagnostic accuracy in identifying tuberculosis infection, the cost and safety, the EC skin test might be a potential candidate for replacing TST in high burden countries or those with routine BCG vaccination. Clinical Trials Registration. ChiCTR2000038622, Safety of the EC skin test to screen tuberculosis infection in two universities, compared with the tuberculin skin test: a double-blind, randomized, controlled trial. registered on 26/09/2020 at http://www.chictr.org.cn.

Sensitivity, specificity, and safety of a novel ESAT6-CFP10 skin test for tuberculosis infection in China: two randomized, self-controlled, parallel-group phase 2b trials

BACKGROUND

Diagnostics to identify tuberculosis infection are limited. We aimed to assess the diagnostic accuracy and safety of the novel ESAT6-CFP10 (EC) skin test for tuberculosis infection in Chinese adults.

METHODS

We conducted two randomized, parallel-group clinical trials in healthy participants and tuberculosis patients. All participants were tested with the T-SPOT.TB test, then received EC skin test and tuberculin skin test (TST). The diameter of skin indurations and/or redness at injection sites were measured at different time periods. A Bacillus Calmette Guerin (BCG) model was also established to assess the diagnosis of tuberculosis infection using EC skin test.

RESULTS

In total, 777 healthy participants and 96 tuberculosis patients were allocated to receive the EC skin test at 1.0μg/0.1ml or 0.5μg/0.1ml. The area under the curve was 0.95 (95% CI, 0.91-0.97) from the EC skin test at a dose of 1.0μg/0.1ml at 24-72 hours. Compared to the T-SPOT.TB test, the EC skin test demonstrated similar sensitivity (87.5, 95% CI 77.8-97.2 versus 86.5, 95% CI 79.5-93.4) and specificity (98.9, 95% CI 96.0-99.9 versus 96.1, 95% CI 93.5-97.8). Among BCG vaccinated participants, the EC skin test had high consistency with the T-SPOT.TB test (96.3, 95% CI, 92.0-100.0). No serious adverse events related to the EC skin test were observed.

CONCLUSIONS

The EC skin test demonstrated both high specificity and sensitivity at a dose of 1.0μg/0.1ml, comparable to the T-SPOT.TB test. The diagnostic accuracy of the EC skin test was not impacted by BCG vaccination.

Impaired T-cell and antibody immunity after COVID-19 infection in chronically immunosuppressed transplant recipients

Assessment of T-cell immunity to the COVID-19 coronavirus requires reliable assays and is of great interest, given the uncertain longevity of the antibody response. Some recent reports have used immunodominant spike (S) antigenic peptides and anti-CD28 co-stimulation in varying combinations to assess T-cell immunity to SARS-CoV-2. These assays may cause T-cell hyperstimulation and could overestimate antiviral immunity in chronically immunosuppressed transplant recipients, who are predisposed to infections and vaccination failures. Here, we evaluate CD154-expressing T-cells induced by unselected S antigenic peptides in 204 subjects-103 COVID-19 patients and 101 healthy unexposed subjects. Subjects included 72 transplanted and 130 non-transplanted subjects. S-reactive CD154+T-cells co-express and can thus substitute for IFNγ (n=3). Assay reproducibility in a variety of conditions was acceptable with coefficient of variation of 2-10.6%. S-reactive CD154+T-cell frequencies were a) higher in 42 healthy unexposed transplant recipients who were sampled pre-pandemic, compared with 59 healthy non-transplanted subjects (p=0.02), b) lower in Tr COVID-19 patients compared with healthy transplant patients (p<0.0001), c) lower in Tr patients with severe COVID-19 (p<0.0001), or COVID-19 requiring hospitalization (p<0.05), compared with healthy Tr recipients. S-reactive T-cells were not significantly different between the various COVID-19 disease categories in NT recipients. Among transplant recipients with COVID-19, cytomegalovirus co-infection occurred in 34%; further, CMV-specific T-cells (p<0.001) and incidence of anti-receptor-binding-domain IgG (p=0.011) were lower compared with non-transplanted COVID-19 patients. Healthy unexposed transplant recipients exhibit pre-existing T-cell immunity to SARS-CoV-2. COVID-19 infection leads to impaired T-cell and antibody responses to SARS-CoV-2 and increased risk of CMV co-infection in transplant recipients.

Male Sex Bias in Immune Biomarkers for Tuberculosis

Males have a bias toward developing sputum smear-positive pulmonary tuberculosis, whereas other forms of the disease have an equal sex ratio. Immune responses are known to be affected by estrogen and testosterone. Biomarkers may therefore be affected by these hormones, especially between 16 and 45 years of age when the differences are most marked. Using large data sets, we examined whether the male bias was significant in terms of diagnosis or predictive ability for the development of disease in those exposed to tuberculosis. Despite the large numbers, the need to specify homogeneous population groups for analysis affected the statistical power to discount a useful biomarker. In general, males showed higher interferon-gamma responses to TB antigens ESAT-6 and CFP-10, whilst females had stronger tuberculin responses in those with sputum smear- and culture-positive tuberculosis, but smaller responses in those who were screened for tuberculosis and who did not develop disease. Importantly, in contacts of sputum smear-positive pulmonary tuberculosis, more males who did not develop tuberculosis had tuberculin skin tests in the range between 10 and 14 mm, suggesting that sex-specific cut-offs might be better than general cut-off values for determining who should receive preventive treatment. Immunocytochemistry of the tuberculin responses correlated with cell numbers only in females. Total and anti-lipoarabinomannan IgM antibody levels were lower in males, whereas total and anti-BCG IgE antibody levels were higher. Evaluation of biomarkers should take account of the spectrum of tuberculosis and male sex bias for sputum smear-positive pulmonary tuberculosis. These findings improve our understanding of how immune responses contribute to the pathogenesis of infectious tuberculosis as well as suggesting clinical applications of the differences between the sexes.

Frequency of and risk factors for reversion of QuantiFERON test in healthcare workers in an intermediate-tuberculosis-burden country

OBJECTIVES

High-risk healthcare workers (HCWs) are often screened for latent tuberculosis infection (LTBI) using QuantiFERON tests (QFTs), with annual serial tests often showing reversion from positive to negative results. We assessed the frequency of and risk factors for reversion of QFTs in HCWs in an intermediate-tuberculosis burden country.

METHODS

We enrolled high-risk HCWs at a tertiary-care hospital in South Korea, who were assessed by QFTs at least twice between 2017 and 2019.

RESULTS

Of the 1870 HCWs screened, 1542 (82%) had persistent negative results, 229 (12%) had persistent positive results, 53 (3%) showed reversion, and 46 (2%) showed conversion from negative to positive. Multivariate analysis comparing the characteristics of the 229 HCWs with persistent positive results and the 53 who experienced reversion showed that older age (adjusted odds ratio (aOR): 0.96; 95% confidence interval (CI): 0.92-0.99), male sex (aOR: 0.29; 95% CI: 0.11-0.78) and high (≥0.70 IU/mL) baseline QFT results (aOR: 0.15; 95% CI: 0.07-0.31) were inversely associated with reversion. Using an ROC curve-derived cut-off of <0.738 IU/mL, the area under the curve was 0.79. Of 53 HCWs with reversion, 36 (78%) had below 0.738 IU/mL of baseline QFT, while 181 (79%) of 229 HCWs without reversion had above 0.738 IU/mL of baseline QFT.

CONCLUSION

Reversion during serial testing is unlikely in HCWs who are male, older in age, and have higher baseline QFT results. Serial testing without LTBI treatment may be indicated in HCWs who are female, younger and, especially, have lower QFT results.

Diagnosis for Latent Tuberculosis Infection: New Alternatives

Latent tuberculosis infection (LTBI) is a subclinical mycobacterial infection defined on the basis of cellular immune response to mycobacterial antigens. The tuberculin skin test (TST) and the interferon gamma release assay (IGRA) are currently used to establish the diagnosis of LTB. However, neither TST nor IGRA is useful to discriminate between active and latent tuberculosis. Moreover, these tests cannot be used to predict whether an individual with LTBI will develop active tuberculosis (TB) or whether therapy for LTBI could be effective to decrease the risk of developing active TB. Therefore, in this article, we review current approaches and some efforts to identify an immunological marker that could be useful in distinguishing LTBI from TB and in evaluating the effectiveness of treatment of LTB on the risk of progression to active TB.

High reproducibility of the interferon-gamma release assay T-SPOT.TB in serial testing

Longitudinal studies regarding the reproducibility of Interferon-gamma release assay (IGRA) T-SPOT.TB for the diagnosis of Mycobacterium tuberculosis (M. tb) infection in serial testing are limited. We retrospectively analysed results of serially tested subjects in a medical laboratory in Germany over a time period of 14 years. From October 2004 to December 2018, a total of 5440 subjects were identified with a second T-SPOT.TB test after a median time interval of 258 days (interquartile range [IQR] 62-665). Consistently negative (n = 4520) or positive results (n = 682) were observed in 5202 (95.6%) subjects, indicating a high degree of concordance in serial testing (κ = 0.83). Test conversions occurred in 101 of 4621 (2.2%) subjects with initially negative tests. Of 819 subjects with initially positive test results, 137 (16.7%) had a test reversion which was associated with low spot numbers of the first test. Of 529 subjects retested within 1 year, only 60 (11.3%) displayed a test reversion. In subjects retested after more than 1 year, 77 of 290 (26.6%) tests reverted. This significantly higher rate of test reversions after more than 1 year was age-dependent and only observed in subjects above the age of 40 years. In the medical laboratory, the T-SPOT.TB test demonstrates a high reproducibility in serial testing.

Performance of Interferon-Gamma Release Assays for Tuberculosis Screening in Pediatric Inflammatory Bowel Disease

OBJECTIVES

The aim of the study was to analyze the diagnostic accuracy and utility of QuantiFERON-TB Gold In-Tube, an interferon-gamma release assay (IGRA), as a screening tool for latent tuberculosis infection (LTBI) in pediatric patients with inflammatory bowel disease (IBD) undergoing treatment with anti-tumor necrosis factor (anti-TNF) medications. To describe cases of tuberculosis in the pediatric IBD population, TB treatment courses, outcomes, and their effect on IBD management.

METHODS

A single-center, retrospective cohort study of pediatric IBD patients who underwent tuberculosis screening. IGRA testing from 2011 to 2017 were analyzed to determine result rates, characteristics, and outcomes.

RESULTS

One thousand seven hundred fifty-four (1,754) tests were performed on 859 patients. One thousand six hundred thirty-four (1,634) tests were negative, 9 were positive, and 111 were indeterminate. Eight of 9 positive tests resulted during repeat annual screening while receiving IBD treatment. Five patients were treated for latent tuberculosis infection (LTBI), and 4 were false-positives. IBD therapy was interrupted in 3 patients, with no negative long-term outcomes. We report 1 known false-negative, in a patient who developed disseminated TB on anti-TNF therapy. Indeterminate testing rates were higher at IBD diagnosis than during treatment (10.3% vs 5.3%, P < 0.001). Follow-up testing of indeterminate results was negative in all patients retested, with 14 patients lost to follow-up. No patient with indeterminate testing developed TB.

CONCLUSIONS

IGRAs are a useful tool to screen for LTBI, both before anti-TNF therapy and during treatment. Results should be used in concert with detailed history and examination. Positive and indeterminate results should be promptly repeated for timely TB diagnosis and to minimize interruptions in IBD therapy.

A novel strategy for interpreting the T-SPOT.TB test results read by an ELISPOT plate imager

Background

The T-SPOT.TB can be read by an ELISPOT plate imager as an alternative to a labor-intensive and time-consuming manual reading, but its accuracy has not been sufficiently discussed to date.

Methods

1,423 test results obtained from manual reading using a microscope and an ELISPOT plate imager were compared. The agreement of qualitative test results was assessed using Cohen's kappa coefficient. The relationship of spot counts was studied using Bland-Altman analysis.

Results

The overall percent agreement of the qualitative test results was 95.43% with a kappa coefficient of 0.91. Positive test results with the maximum net spot count of 8 and borderline test results showed relatively high discordance. The agreement of spot counts in panel A, panel B, and nil control was good, and variability did not increase with higher spot counts. On the basis of study findings, a novel strategy for interpreting the test results by an ELISPOT plate imager was proposed.

Conclusions

To increase diagnostic accuracy, positive test results with the maximum net spot count of 8 and borderline test results should be manually confirmed. Our strategy could be a practical guide for laboratories to build their own strategies for interpreting the test results by an ELISPOT plate imager.

Reproducibility of the T-SPOT.TB test for screening Mycobacterium tuberculosis infection in Japan

OBJECTIVES

The interferon-gamma release assay (IGRA) is useful for diagnosing Mycobacterium tuberculosis infections, especially in countries where Bacille Calmette-Guérin vaccinations are performed. However, reproducibility of the IGRA is unclear, as recent data suggest high IGRA conversion and reversion rates in serial tests among healthcare workers. This longitudinal study aimed to evaluate reproducibility of T-SPOT.TB for screening M. tuberculosis infections in Japan.

METHODS

Results of T-SPOT.TB tests performed between April 2014 and March 2016 at two hospitals in Yokohama, Japan, where the incidence of tuberculosis was 18.0 per 100,000 population in 2014, were analyzed.

RESULTS

In total, 3890 T-SPOT.TB tests were included. Overall, positive and negative test rates were 8.4% and 87.6%, respectively. Among 373 serial tests within two years, conversion and reversion rates were only 1.1% and 12.5%, respectively. Almost all patients who were initially negative (98.9%) remained so. There was no statistically significant difference between the outcomes observed at the two hospitals.

CONCLUSIONS

The conversion rate of T-SPOT.TB in Japan is as low as that recently reported in other countries where the incidence of tuberculosis is low. These data indicate that T-SPOT.TB is a reproducible tuberculosis screening tool at local hospitals in areas with a moderate incidence of tuberculosis.

T-SPOT.TB Performance in Routine Pediatric Practice in a Low TB Burden Setting

BACKGROUND

The T-SPOT.TB, an interferon-gamma release assay, is an indirect test of Mycobacterium tuberculosis infection. Due to sparse and conflicting evidence, the use of interferon-gamma release assay is limited in young and HIV-infected children. We determined the prevalence of invalid, borderline, positive and negative results and associations with key demographic variables during routine pediatric use in a low tuberculosis burden setting.

METHODS

For pediatric samples received at Oxford Diagnostic Laboratories between 2010 and 2015, the associations between initial test outcome and demographics were estimated by bivariate analysis and logistic regression.

RESULTS

A total of 44,289 samples (median age 12.5 years; interquartile range 7.7-15.5), including 5057 samples (11.6%) from children under 5 years old, were received from 46 U.S. states, Washington, DC and Puerto Rico. A total of 592 samples (1.3%) could not be tested. T-SPOT.TB positivity was strongly correlated (r = 0.60; P < 0.0001) with state TB incidence. Compared with negative results, positive results were more likely in samples from older children (P < 0.0001), public health clinics (P < 0.0001) and rural locations (P = 0.005). Although infrequent (0.6%), invalid results were more common in samples collected at HIV clinics (odds ratio = 2.5, 95% confidence interval: 1.3-4.9) and from younger children (P = 0.03). These invalid results were more likely due to a robust nil (negative) control response rather than a weak mitogen (positive) control response.

CONCLUSIONS

The T-SPOT.TB test correlated strongly with well-recognized risk factors for tuberculosis infection and provided evaluable results in 98% of children. To optimize the impact of testing on clinical decision making and patient outcomes, local epidemiology and individual patient risk should be considered when incorporating IGRAs into pediatric guidelines.

Application of molecular, microbiological, and immunological tests for the diagnosis of bone and joint tuberculosis

BACKGROUND

To evaluate the application of interferon gamma release assay (IGRA), rifampicin resistant real-time fluorescence quantitative PCR technique Xpert Mycobacterium tuberculosis/rifampicin (Xpert MTB/RIF), and the levels of TNF-α and TGF-β in the diagnosis of bone and joint tuberculosis.

METHODS

Eighty-six patients with bone and joint tuberculosis, diagnosed by pathology or microbiology, were examined by Xpert MTB/RIF and IGRA (T-SPOT. TB) for Mycobacterium tuberculosis infection, and the TNF-α and TGF-β levels of the patients were measured.

RESULTS

The sensitivity of IGRA in diagnosing bone and joint tuberculosis was 81.4%; Xpert MTB/RIF's sensitivity was 70.9%. The combined sensitivity of the two methods was 91.9%. The combined detection sensitivity of the two methods was higher than individual IGRA or Xpert MTB/RIF detection sensitivity. The TNF-α and TGF-β levels in bone and joint tuberculosis patients were higher than those in the control group.

CONCLUSION

Xpert MTB/RIF, IGRA, TNF-α, and TGF-βs expression have value in the rapid diagnosis of bone and joint tuberculosis, and the sensitivity and accuracy of bone and joint tuberculosis diagnosis by combining them can improve it.

Practice Guidelines for Clinical Microbiology Laboratories: Mycobacteria

Mycobacteria are the causative organisms for diseases such as tuberculosis (TB), leprosy, Buruli ulcer, and pulmonary nontuberculous mycobacterial disease, to name the most important ones. In 2015, globally, almost 10 million people developed TB, and almost half a million patients suffered from its multidrug-resistant form. In 2016, a total of 9,287 new TB cases were reported in the United States. In 2015, there were 174,608 new case of leprosy worldwide. India, Brazil, and Indonesia reported the most leprosy cases. In 2015, the World Health Organization reported 2,037 new cases of Buruli ulcer, with most cases being reported in Africa. Pulmonary nontuberculous mycobacterial disease is an emerging public health challenge. The U.S. National Institutes of Health reported an increase from 20 to 47 cases/100,000 persons (or 8.2% per year) of pulmonary nontuberculous mycobacterial disease among adults aged 65 years or older throughout the United States, with 181,037 national annual cases estimated in 2014. This review describes contemporary methods for the laboratory diagnosis of mycobacterial diseases. Furthermore, the review considers the ever-changing health care delivery system and stresses the laboratory's need to adjust and embrace molecular technologies to provide shorter turnaround times and a higher quality of care for the patients who we serve.

Use of interferon-gamma release assay and tuberculin skin test in diagnosing tuberculosis in Lithuanian adults: A comparative analysis

BACKGROUND AND OBJECTIVE

Lithuania belongs to the group of countries with a high-incidence of tuberculosis (TB). Some scientific studies show that the interferon-gamma release assay is more accurate and correlates more highly with TB exposure as compared to the tuberculin skin test (TST). This study aimed at comparing the efficacy between the T SPOT TB and TST for diagnosing TB among Lithuanian adults.

MATERIALS AND METHODS

Individuals with diagnosed TB, healthcare workers with known risk for TB and individuals without any known risk for TB underwent clinical examinations, interviews about their history of TB exposure and chest radiography. Then the TST and the T SPOT TB were performed on patients.

RESULTS

A positive T SPOT TB was more common in the group with diagnosed TB compared to healthcare workers and the low risk for TB groups (97.5%, 36.4%, and 0%, respectively, P<0.01). Positive TST results did not differ between the groups with diagnosed TB and the healthcare workers (92.5% vs. 95.5%, P>0.05). Agreement between TST and T SPOT TB was poor (kappa 0.14, P>0.05). T SPOT TB had higher specificity and sensitivity compared to TST (area under the ROC 0.9±0.04, P<0.01, vs. 0.5±0.06, P>0.05).

CONCLUSIONS

The T SPOT TB showed greater accuracy in diagnosing TB than TST did. Positive T SPOT TB result but not the TST was more common in patients with diagnosed TB.

Revisiting annual screening for latent tuberculosis infection in healthcare workers: a cost-effectiveness analysis

BACKGROUND

In North America, tuberculosis incidence is now very low and risk to healthcare workers has fallen. Indeed, recent cohort data question routine annual tuberculosis screening in this context. We compared the cost-effectiveness of three potential strategies for ongoing screening of North American healthcare workers at risk of exposure. The analysis did not evaluate the cost-effectiveness of screening at hiring, and considered only workers with negative baseline tests.

METHODS

A decision analysis model simulated a hypothetical cohort of 1000 workers following negative baseline tests, considering duties, tuberculosis exposure, testing and treatment. Two tests were modelled, the tuberculin skin test (TST) and QuantiFERON®-TB-Gold In-Tube (QFT). Three screening strategies were compared: (1) annual screening, where workers were tested yearly; (2) targeted screening, where workers with high-risk duties (e.g. respiratory therapy) were tested yearly and other workers only after recognised exposure; and (3) post exposure-only screening, where all workers were tested only after recognised exposure. Workers with high-risk duties had 1% annual risk of infection, while workers with standard patient care duties had 0.3%. In an alternate higher-risk scenario, the corresponding annual risks of infection were 3% and 1%, respectively. We projected costs, morbidity, quality-adjusted survival and mortality over 20 years after hiring. The analysis used the healthcare system perspective and a 3% annual discount rate.

RESULTS

Over 20 years, annual screening with TST yielded an expected 2.68 active tuberculosis cases/1000 workers, versus 2.83 for targeted screening and 3.03 for post-exposure screening only. In all cases, annual screening was associated with poorer quality-adjusted survival, i.e. lost quality-adjusted life years, compared to targeted or post-exposure screening only. The annual TST screening strategy yielded an incremental cost estimate of $1,717,539 per additional case prevented versus targeted TST screening, which in turn cost an incremental $426,678 per additional case prevented versus post-exposure TST screening only. With the alternate "higher-risk" scenario, the annual TST strategy cost an estimated $426,678 per additional case prevented versus the targeted TST strategy, which cost an estimated $52,552 per additional case prevented versus post-exposure TST screening only. In all cases, QFT was more expensive than TST, with no or limited added benefit. Sensitivity analysis suggested that, even with limited exposure recognition, annual screening was poorly cost-effective.

CONCLUSIONS

For most North American healthcare workers, annual tuberculosis screening appears poorly cost-effective. Reconsideration of screening practices is warranted.

QFT-Plus: a plus in variability? - Evaluation of new generation IGRA in serial testing of students with a migration background in Germany

BACKGROUND

Currently available Interferon-gamma release assays (IGRAs) show a considerable variability in serial testing for latent tuberculosis infection (LTBI). This study offers first results for the new generation IGRA QuantiFERON-TB Gold Plus (QFT-Plus) introduced in 2015 in comparison with its predecessor QuantiFERON-TB Gold In-Tube (QFT-GIT) from serial testing of students with a migration background at German universities.

METHODS

Forty-one students were selected from a previous study. All students with a positive IGRA were asked and 11 agreed to participate in this cohort study. Additionally 30 students with negative IGRA results were selected by chance. Weekly testing with QFT-Plus and QFT-GIT was performed in all individuals over a 4-week period. IGRA variability was evaluated by calculating conversion and reversion rates.

RESULTS

From 41 participants a total number of 163 serial measurements were analyzed for each IGRA, leading to 122 possible IGRA changes each. QFT-Plus had four conversions and two reversions leading to a conversion rate of 4.3% (4 of 93 possible conversions, 95% CI 1.4-11.3%) and reversion rate of 6.9% (2 of 29 possible reversions, 95% CI 1.2-24.2%). QFT-GIT had 2 conversions and 1 reversion causing slightly lower rates with 2.2% conversions (2 of 91, 95% CI 0.4-8.5%) and 3.2% reversions (1 of 31, 95% CI 0.2-18.5%). Inconsistent IGRA results occurred in 4 subjects for QFT-Plus (8 stable positives, 29 stable negatives) and in 2 subjects for QFT-GIT (9 stable positives, 30 stable negatives). Agreement between the two IGRAs was 95.1% (κ = 0.89). Variance attributed to the individuals was low (QFT-Plus: ICC = 0.88).

CONCLUSION

This study confirms occurrence of conversions and reversions for the new QFT-Plus in serial testing of a high-risk cohort in a low-incidence setting with improbable new TB contact during the study. QFT-Plus conversion and reversion rates were slightly higher than for the QFT-GIT but overall they were lower for both IGRAs than in other studies that investigated IGRA variability.

The Direct Comparison of Two Interferon-gamma Release Assays in the Tuberculosis Screening of Japanese Healthcare Workers

Objective Two interferon-gamma release assays (IGRAs), the QuantiFERON-TB Gold In-Tube (QFT-GIT) and T-SPOT.TB (T-SPOT), are commercially available. The agreement between the two IGRAs in the screening of healthcare workers (HCWs) for latent tuberculosis is not well known. Methods The QFT-GIT and T-SPOT tests were performed for the baseline tuberculosis screening of 654 HCWs who worked at Mie University Hospital in Japan. The results of the two tests were directly compared. Results Nineteen (2.9%), 28 (4.3%) and 33 (5.0%) of the 654 HCWs were found to be positive by the QFT-GIT, T-SPOT, and the QFT-GIT and/or T-SPOT methods using cut-off values of 0.35 IU/mL (QFT-GIT) and 6 spots (T-SPOT). After excluding 4 cases with indeterminate results, there were 14 concordant positive (2.2%), 618 concordant negative (95.1%), and 18 discordant (2.8%) results using the cut-off values of 0.35 IU/mL (QFT-GIT) and 6 spots (T-SPOT). The agreement of the two IGRAs was 97.2% (κ=0.595). When cut-off values of 0.35 IU/mL (QFT-GIT) and 8 spots (T-SPOT) were applied, there were 11 concordant positive (1.7%), 626 concordant negative (96.3%), and 13 discordant (2.0%) results, with 98.0% agreement (κ=0.618). When the borderline criteria for the QFT-GIT (0.1 to <0.35 IU/mL) and T-SPOT (5-7 spots) were applied, there were 11 concordant positive (1.7%), 11 concordant borderline (1.7%), 586 concordant negative (90.2%), and 42 discordant (6.5%) results, with 93.5% agreement between the two methods (κ=0.538). Conclusion When standard cut-off values were used, the agreement between the two IGRAs in the tuberculosis screening of Japanese HCWs was moderate to high. Importantly, some HCWs showed discordant results, especially those whose results were in the borderline zones.

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.

Hepatic and Intra-abdominal Tuberculosis: 2016 Update

Mycobacterium tuberculosis (TB) infection affects nearly 10 million people a year and causes 1.5 million deaths. TB is common in the immunosuppressed population with 12 % of all new diagnoses occurring in human immune deficiency virus (HIV)-positive patients. Extra-pulmonary TB occurs in 12 % of patients with active TB infection of which 3.5 % is hepatobiliary and 6-38 % is intra-abdominal. Hepatobiliary and intra-abdominal TB can present with a myriad of non-specific symptoms, and therefore, diagnosis requires a high level of suspicion. Accurate and rapid diagnosis requires a multidisciplinary team (MDT) approach using radiology, interventional radiology, surgery and pathology services. Treatment of TB is predominantly medical, yet surgery plays an important role in managing the complications of hepatobiliary and intra-abdominal TB.

Differential positive TSPOT assay responses to ESAT-6 and CFP-10 in health care workers

BACKGROUND

The TSPOT.TB (TSPOT) diagnostic test for latent tuberculosis infection is based on a cell-mediated response to the Mycobacteria tuberculosis antigens, ESAT-6 and/or CFP-10, producing an "interferon-gamma footprint". We investigated the within-sample and within-subject variability of positive TSPOT assays due to the individual assay antigens' reactivity.

METHODS

Positive TSPOT assay frequencies due to ESAT-6 or CFP-10 among health care workers (HCWs) at 6-month intervals for 18 months were compared. Differences in result interpretation (positive or negative) for ESAT-6 and CFP10 and potential prognostic factors were investigated.

RESULTS

There were 576 positive results in 8805 TSPOT assays representing 2418 participants. A significant difference was detected in positive TSPOT results due to a positive response to either ESAT-6, CFP-10 or both antigens at baseline through 12 M (p < 0.001), but not for the 18 M follow-up. Gender, ethnicity, occupation, previous positive tuberculin skin test (TST) and study site were significantly associated with specific antigen positivity.

CONCLUSIONS

Among our HCW samples with positive TSPOT assays, CFP-10 induced a larger proportion of positive TSPOT results than ESAT-6. Potential causes for this finding include: BCG vaccinated subpopulations, certain jobs, history of positive TST, U.S. birth, and study site. A high proportion of single-positive specimens may reflect false-positives results.

Interferon Gamma Release Assays for Latent Tuberculosis: What Are the Sources of Variability?

Interferon gamma release assays (IGRAs) are blood-based tests intended for diagnosis of latent tuberculosis infection (LTBI). IGRAs offer logistical advantages and are supposed to offer improved specificity over the tuberculin skin test (TST). However, recent serial testing studies of low-risk individuals have revealed higher false conversion rates with IGRAs than with TST. Reproducibility studies have identified various sources of variability that contribute to nonreproducible results. Sources of variability can be broadly classified as preanalytical, analytical, postanalytical, manufacturing, and immunological. In this minireview, we summarize known sources of variability and their impact on IGRA results. We also provide recommendations on how to minimize sources of IGRA variability.