Association between interferon-gamma (IFN-γ) gene polymorphisms and tuberculosis susceptibility: a systematic review and meta-analysis

Interferon-gamma (IFN-γ) has been established to play a pivotal role in the pathogenesis of tuberculosis (TB). Existing evidence suggests a potential association between the genetic poly-morphisms of IFN-γ and the susceptibility to TB. However, this association remains a topic of controversy. To address this knowledge gap, a meta-analysis was conducted to provide more accurate results regarding their relationship. The pooled odds ratio along with its corresponding 95% confidence interval was calculated using four different gene models. This analytical approach served to evaluate the strength of the association between single nucleotide polymorphisms (SNPs) and TB susceptibility. Additionally, we determined whether a fixed effect model or a random effect model should be applied based on the extent of heterogeneity. Egger's test was used to evaluate publication bias. This study included a total of nine studies, involving 4509 patients with TB and 4378 healthy controls. In non-Asian populations, a C > T mutation at polymorphic variant rs2069705 and a T > C mutation at rs2069718 was associated with an increased risk of TB. Conversely, among Asians, the variants rs2069705, rs2069718, and rs1861494 were not significantly associated with the risk of TB. Importantly, our investigation did not reveal any significant publication bias in the pooled results of the four gene models. In conclusion, this meta-analysis suggests that two SNPs in IFN-γ may be associated with TB susceptibility in non-Asian populations. However, for Asians, there is no evidence to support a conclusive relationship between these SNPs and the risk of TB.

Challenges and the Way forward in Diagnosis and Treatment of Tuberculosis Infection

Globally, it is estimated that one-quarter of the world's population is latently infected with Mycobacterium tuberculosis (Mtb), also known as latent tuberculosis infection (LTBI). Recently, this condition has been referred to as tuberculosis infection (TBI), considering the dynamic spectrum of the infection, as 5-10% of the latently infected population will develop active TB (ATB). The chances of TBI development increase due to close contact with index TB patients. The emergence of multidrug-resistant TB (MDR-TB) and the risk of development of latent MDR-TB has further complicated the situation. Detection of TBI is challenging as the infected individual does not present symptoms. Currently, there is no gold standard for TBI diagnosis, and the only screening tests are tuberculin skin test (TST) and interferon gamma release assays (IGRAs). However, these tests have several limitations, including the inability to differentiate between ATB and TBI, false-positive results in BCG-vaccinated individuals (only for TST), false-negative results in children, elderly, and immunocompromised patients, and the inability to predict the progression to ATB, among others. Thus, new host markers and Mtb-specific antigens are being tested to develop new diagnostic methods. Besides screening, TBI therapy is a key intervention for TB control. However, the long-course treatment and associated side effects result in non-adherence to the treatment. Additionally, the latent MDR strains are not susceptible to the current TBI treatments, which add an additional challenge. This review discusses the current situation of TBI, as well as the challenges and efforts involved in its control.

Biomarkers to identify Mycobacterium tuberculosis infection among borderline QuantiFERON results

BACKGROUND

Screening for tuberculosis (TB) infection often includes QuantiFERON-TB Gold Plus (QFT) testing. Previous studies showed that two-thirds of patients with negative QFT results just below the cut-off, so-called borderline test results, nevertheless had other evidence of TB infection. This study aimed to identify a biomarker profile by which borderline QFT results due to TB infection can be distinguished from random test variation.

METHODS

QFT supernatants of patients with a borderline (≥0.15 and <0.35 IU·mL-1), low-negative (<0.15 IU·mL-1) or positive (≥0.35 IU·mL-1) QFT result were collected in three hospitals. Bead-based multiplex assays were used to analyse 48 different cytokines, chemokines and growth factors. A prediction model was derived using LASSO regression and applied further to discriminate QFT-positive Mycobacterium tuberculosis-infected patients from borderline QFT patients and QFT-negative patients RESULTS: QFT samples of 195 patients were collected and analysed. Global testing revealed that the levels of 10 kDa interferon (IFN)-γ-induced protein (IP-10/CXCL10), monokine induced by IFN-γ (MIG/CXCL9) and interleukin-1 receptor antagonist in the antigen-stimulated tubes were each significantly higher in patients with a positive QFT result compared with low-negative QFT individuals (p<0.001). A prediction model based on IP-10 and MIG proved highly accurate in discriminating patients with a positive QFT (TB infection) from uninfected individuals with a low-negative QFT (sensitivity 1.00 (95% CI 0.79-1.00) and specificity 0.95 (95% CI 0.74-1.00)). This same model predicted TB infection in 68% of 87 patients with a borderline QFT result.

CONCLUSIONS

This study was able to classify borderline QFT results as likely infection-related or random. These findings support additional laboratory testing for either IP-10 or MIG following a borderline QFT result for individuals at increased risk of reactivation TB.

Occupational Infections among Dental Health Workers in Germany-14-Year Time Trends

Dental health workers (DHW) are at increased risk of acquiring occupational infections. Due to various protective measures, it can be assumed that infections have decreased over the past 14 years. Secondary data from a German accident insurance company was analyzed in terms of reported and confirmed occupational diseases (OD) in DHW from 2006 to 2019. A total of 271 claims were reported, of which 112 were confirmed as OD, representing an average of eight per year. However, the number of claims and confirmed ODs has decreased by 65.6% and 85.7%, respectively. The decrease was most evident for hepatitis B (HBV) and C (HCV) infections, while tuberculosis (TB) infections were stable. A total of 44 HCV, 33 HBV, 6 TB and 24 latent TB infections were confirmed as ODs. For DHW, 0.05, and for hospital workers, 0.48 claims per 1000 full-time equivalents (FTE) were registered in 2019. In a separate documentation system, between March 2020 and February 2021, 155 COVID-19 claims were registered, and 47 cases were confirmed as ODs. For DHW, 0.7, and for hospital workers, 47.3 COVID-19 claims per 1000 FTE were registered since 2020. Occupational infectious diseases rarely occur among DHW. Nevertheless, new infectious diseases such as COVID-19 pose a major challenge for DHW. Continued attention should be paid to infectious disease prevention.

Resistance to Mycobacterium tuberculosis Infection Among Household Contacts: A Multinational Study

BACKGROUND

Some contacts of patients with tuberculosis remain negative on tests for tuberculosis infection, despite prolonged exposure, suggesting they might be resistant to Mycobacterium tuberculosis infection. The objective of this multinational study was to estimate the proportion of household contacts resistant to M. tuberculosis (resisters).

METHODS

We conducted a longitudinal study enrolling index patients enrolled in treatment for pulmonary multidrug- or rifampin-resistant tuberculosis and their household contacts. Contacts were tested for tuberculosis infection with a tuberculin skin test (TST) and interferon-gamma release assay (IGRA) at baseline and after 1 year. Exposure was quantified based on index patients' infectiousness, index patient and household contact interaction, and age. We explored multiple definitions of resistance to tuberculosis infection by varying TST negativity cutoffs (0 vs <5 mm), classification of missing test results, and exposure level.

RESULTS

In total, 1016 contacts were evaluated from 284 households; 572 contacts aged ≥5 years had TST and longitudinal IGRA results available. And 77 (13%) or 71 (12%) contacts were classified as resisters with a <5 mm or 0 mm TST threshold, respectively. Among 263 highly exposed contacts, 29 (11%) or 26 (10%) were classified as resisters using TST cutoffs of <5 mm and 0 mm, respectively. The prevalence of resisters did not differ substantially by sex, age, human immunodeficiency virus (HIV) coinfection, or comorbid conditions.

CONCLUSIONS

At least 10% of household contacts can be classified as resistant to tuberculosis infection, depending on the definition used, including those with high exposure. Further studies to understand genetic or immunologic mechanisms underlying the resister phenotype may inform novel strategies for therapeutics and vaccines.

Tuberculosis Infection Screening in 5468 Italian Healthcare Students: Investigation of a Borderline Zone Value for the QFT-Test

Healthcare workers are at an increased risk of contracting Mycobacterium tuberculosis infection. Tuberculin skin test (TST) and interferon gamma release assay (IGRA) represent the available tests most used for the diagnosis of latent tuberculosis infection (LTBI). Different borderline zones have been proposed for defining conversions and reversions to improve the interpretation of the IGRA test results as part of serial testing. From 2012 to 2017, 5468 health students of an Italian University Hospital were screened for tuberculosis infection through the execution of the TST and, in case of positivity, of the QuantiFERON-TB® Gold In-Tube assay (QFT-GIT). The QFT-GIT is considered "borderline" with values from 0.35 to 0.99 IU/mL. Among the students who performed the QFT-GIT assay, 27 subjects presented a range of values defined as borderline. The QFT-GIT was repeated after 90 days on 19 subjects with borderline values and showed a negativization of the values in 14 students and a positive conversion in three cases, while for two students, a borderline value was also found for the second test, with a 74% regression of the borderline cases. The introduction of QuantiFERON borderline values is a useful assessment tool to bring out LTBI case candidates for chemoprophylaxis.

Risk Analysis of Latent Tuberculosis Infection among Health Workers Compared to Employees in Other Sectors

Latent tuberculosis infection (LTBI) represents a work-related risk for health workers (HWs). Tuberculosis remains the second most common occupational infectious disease among HWs in Germany. Comparative figures on LTBI prevalence in the general population are missing because testing is only carried out in the context of an outbreak situation. The objective of this study is to investigate whether HWs are at greater risk of LTBI than workers in other sectors. This study is based on two samples. The first sample is a database of HWs who were examined by the German Occupational Physicians Network using an interferon-gamma release assay (IGRA). The second sample consists of general employees (non-health workers, non-HWs) from Hamburg who had no professional contact with the health care system. Propensity score matching (PS matching) was performed to ensure better comparability of the groups. The differences in the prevalence of positive test results from IGRAs were examined using univariate and multivariate analyses. After the PS matching of 1:10, 100 test subjects in the non-HW group and 1000 HWs remained to form the analysis collective. The HWs tended to exhibit higher IGRA values than non-HWs. The univariate analysis showed an odds ratio (OR) of 3.86 for the HWs (95% confidence interval (CI): 0.99 to 32.5; p = 0.056) with respect to a positive test result. The multivariate analysis produced an OR of 4.92, (95% CI: 1.3 to 43.7; p = 0.013) for HWs born in Germany. Despite the declining tuberculosis incidence rates in Germany, a comparison with non-exposed professional groups showed that HWs are at greater risk of LTBI. Preventive medical check-ups still seem to be indicated.

Reactivation of TB during administration of durvalumab after chemoradiotherapy for non-small-cell lung cancer: a case report

Background: Tuberculosis (TB) is considered to be an adverse effect of treatment with immune checkpoint inhibitors. Methodology & results: Our case was a 75-year-old woman diagnosed with unresectable stage III non-small-cell lung cancer. After radical chemoradiotherapy was completed, durvalumab was initiated as a consolidation therapy. However, since chest CT showed appearances of infiltration shadows scattered in the periphery of the lungs after five doses of immunotherapy, duruvalumab was discontinued. 6 weeks later, the patient was aware of intermittent fever. Chest CT scan showed the appearance of a tree-in-bud pattern in the right lung. Acid-fast bacilli stain of sputum was positive and the PCR test was positive for Mycobacterium tuberculosis. Conclusion: Duruvalumab as PD-L1 blockade may activate TB.

Conversion and Reversion Rates of Tuberculosis Screening Assays in Patients With Rheumatic Diseases and Negative Baseline Screening Under Long-Term Biologic Treatment

Background:

To determine the conversion and reversion rates of tuberculosis (TB) screening tests (Tuberculin Skin Test-TST, Interferon Gamma Release Assay-IGRA: T-SPOT.TB) during biologic treatment in patients with rheumatic diseases and negative baseline screening.

Methods:

This was a long-term, longitudinal cohort study of 50 patients with rheumatic diseases and negative baseline TB screening (TST: < 5 mm, negative T-SPOT.TB) treated with tumor necrosis factor inhibitors (TNFi) or other non-TNFi biologics. Patients were rescreened at a mean time of 1.4 (first rescreening) and 6.9 (second rescreening) years from baseline, with both assays. The conversion (negative to positive) and reversion (positive to negative) rate was calculated for each TB screening test.

Results:

Fifty patients (mean age = 60 years) with various rheumatic diseases (rheumatoid arthritis: n = 24, spondyloarthropathies: n = 23, other: n = 3) were enrolled. During the first phase (baseline to first rescreening), all patients were treated with TNFi while during the second phase (first to second rescreening), TNFi (54%) and non-TNFi (46%) were used. Fifteen patients (30%) displayed conversion of at least 1 screening assay during follow-up (10 at the first and 5 at the second rescreening). This conversion rate was higher with TST (n = 11, 22% or 3.47/100 patient-years) compared to T-SPOT.TB (n = 4, 8% or 1.74/100 patient-years). Among the 10 converters at the first rescreening, 5 received isoniazid (INH) preventive therapy and 5 did not; an equal number of patients (3/5, 60%) reverted to negative with or without INH therapy. None of the patients developed active TB during follow-up (6.9 ± 1.0 years).

Conclusions:

Approximately one-third of patients with rheumatic diseases and negative baseline TB screening developed conversion of at least 1 screening test during long-term biologic treatment. This occurred most often with TST and was usually a transient event. These findings do not support routine serial TB retesting in biologic-treated patients with rheumatic diseases in the absence of TB risk factors.

Effect of HIV-infection on QuantiFERON-plus accuracy in patients with active tuberculosis and latent infection

OBJECTIVE

HIV-infection increases the risk to progress to active-tuberculosis (TB). Detection of latent TB infection (LTBI) is needed to eventually propose preventive-therapy and reduce TB reservoir. QuantiFERON-TB Plus (QFT-Plus)-test identifies LTBI. Currently, only two studies on QFT-Plus accuracy in HIV-infected-population are available in high TB-endemic-countries. Therefore we aimed to evaluate the effect of HIV-infection on QFT-Plus accuracy to detect LTBI in a low TB-endemic-country.

METHODS

We enrolled 465 participants, among the 167 HIV-infected-persons: 32 with active-TB (HIV-TB), 45 remote-LTBI (HIV-LTBI) and 90 at low M. tuberculosis (Mtb)-infection risk. Among the 298 HIV-uninfected-persons: 170 with active-TB, 76 recent-LTBI, 34 remote-LTBI and 18 with low Mtb-infection risk.

RESULTS

QFT-Plus sensitivity was similar in TB regardless of HIV-status. CD4-count did not influence the distribution of IFN-γ values in HIV-TB and HIV-LTBI. Moreover HIV-LTBI and HIV-uninfected remote LTBI had a similar proportion of results in the uncertain range (IFNγ ≥0.2 ≤ 0.7 IU/ml) differently from those LTBI-persons reporting recent-exposure (p = 0.016). Cytometry results demonstrated that CD8-response was similar in HIV-infected- and -uninfected-persons whereas CD4-response was impaired in HIV-infected-persons (p = 0.011).

CONCLUSIONS

HIV-infection does not affect QFT-Plus response in active-TB, whereas the time of exposure influences the proportion of uncertain-results in LTBI.

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.

Variation in interferon-γ production between QFT-Plus and QFT-GIT assays in TB contact investigation

BACKGROUND

Individuals with recent contact with active tuberculosis (TB) patients were screened for latent tuberculosis infection (LTBI) considering their greater relative risk for developing active TB. QuantiFERON®-TB Gold Plus (QFT-Plus) assay offers two TB-specific antigen tubes (TB1 and TB2). TB2 is designed to elicit both CD4 and CD8 T-cell responses. This mechanism could lead to increased sensitivity as compared to the QuantiFERON®-TB Gold In-Tube (QFT-GIT) assay. Our objective was to compare the LTBI diagnostic capability of QFT-Plus with that of QFT-GIT.

METHODS

A total of 412 TB contacts (median age 44 years) were prospectively enrolled. We conducted both QFT-Plus and QFT-GIT assays concurrently. We also analyzed production of interferon-γ (IFN-γ) in response to TB-specific antigens.

RESULTS

The positivity rates in QFT-Plus and QFT-GIT were 7.5% (95% confidence interval (CI), 5.4-10.5) and 5.8% (CI, 3.9-8.5), respectively, showing a significant difference (P < 0.05). The median (inter-quartile range [IQR]) of IFN-γ_[QFT-Plus]/IFN-γ_[QFT-GIT] was 1.41 (1.00-2.00). QFT-Plus produced 1.4 times IFN-γ.

CONCLUSIONS

QFT-Plus revealed significantly higher positivity rate compared with QFT-GIT, which might be attributed to increased IFN-γ production. The cut-off in both QFT-Plus and QFT-GIT was 0.35 IU/mL. These effects might resulted in the higher positivity rate in QFT-Plus.

Management of Latent Tuberculosis Infection in Children from Developing Countries

Tuberculosis (TB), once widely prevalent throughout the world, experienced falling incidence rates in early twentieth century in developed nations, even before the introduction of anti-TB drugs, attributed to improved hygiene and living conditions. Active TB may develop following fresh infection or activation of latent tuberculosis infection (LTBI). LTBI is a state of persistent bacterial viability, however, the host stays asymptomatic and there is no evidence of clinically active tuberculosis. Therefore, treatment of all LTBI is considered as one of the ways to control tuberculosis. Diagnosis of LTBI relies on presence of immune-reactivity to TB antigen and commonly used tests include tuberculin skin test and interferon gamma release assay (IGRA). At present there is no diagnostic test that can identify an individual with LTBI who will progress to develop active disease or remain asymptomatic. Therefore, it is unclear whom to treat. In the current scenario, treatment for LTBI is restricted to high risk groups which include under-5 y contacts of adults with pulmonary TB. Various regimens for treatment of LTBI are evolving and consist of isoniazid (INH) alone for 6-9 mo or combination of INH and rifampicin for 3-4 mo or once a week combination of rifapentin and INH for 3 mo. There is a need for research to identify LTBI, risk factors for progression of LTBI to active disease and a shorter regimen for treatment.

Effectiveness of interventions for reducing TB incidence in countries with low TB incidence: a systematic review of reviews

AIMS

What is the evidence base for the effectiveness of interventions to reduce tuberculosis (TB) incidence in countries which have low TB incidence?

METHODS

We conducted a systematic review of interventions for TB control and prevention relevant to low TB incidence settings (<10 cases per 100 000 population). Our analysis was stratified according to "direct" or "indirect" effects on TB incidence. Review quality was assessed using AMSTAR2 criteria. We summarised the strength of review level evidence for interventions as "sufficient", "tentative", "insufficient" or "no" using a framework based on the consistency of evidence within and between reviews.

RESULTS

We found sufficient review level evidence for direct effects on TB incidence/case prevention of vaccination and treatment of latent TB infection. We also found sufficient evidence of beneficial indirect effects attributable to drug susceptibility testing and adverse indirect effects (measured as sub-optimal treatment outcomes) in relation to use of standardised first-line drug regimens for isoniazid-resistant TB and intermittent dosing regimens. We found insufficient review level evidence for direct or indirect effects of interventions in other areas, including screening, adherence, multidrug-resistant TB, and healthcare-associated infection.

DISCUSSION

Our review has shown a need for stronger evidence to support expert opinion and country experience when formulating TB control policy.

Occupational adverse effects and protective factors in bronchoscopy

The application of bronchoscopy has resolved a series of diagnostic and treatment challenges in pulmonary diseases. However, the occupational adverse effects experienced by healthcare workers in interventional pulmonology should receive increasing attention. Various aspects of adverse effects in bronchoscopy are often neglected, and healthcare workers frequently ignore guidelines for personal protection against factors such as radiation, smoke, pathogenic microbiological aerosols, cryogenic gas, etc. Thus, there is an urgent need to conduct additional research to establish standards for occupational adverse effects and protective measures related to bronchoscopy.

Positivity rate of interferon-γ release assays for estimating the prevalence of latent tuberculosis infection in renal transplant recipients in Japan

Renal transplant recipients are at increased risk of reactivating latent tuberculosis infection (LTBI) and developing active tuberculosis. QuantiFERON^®-TB Gold Plus (QFT-Plus) has two TB-specific antigens tubes (TB1 and TB2). TB1 elicits CD4 T-cell response, and TB2 elicits both CD4 and CD8 T-cells responses, with expected increased sensitivity. The aim of this study was to estimate the prevalence of LTBI in renal transplant recipients in Japan. We conducted a cross-sectional study by using two interferon-γ release assays (IGRAs), QFT-Plus and T-SPOT^®.TB (TSPOT). One hundred thirty-five recipients were prospectively enrolled. The median age was 49 years (range: 20 to 79). The positivity rates of QFT-Plus and TSPOT were 5.9% (95%CI 3.0-11.3) and 3.7% (95%CI 1.6-8.4), respectively, with no significant difference. The concordance rate was 95.5% (κ coefficient, 0.76). Age of 60 years and higher was related to the higher positivity rate in both QFT-Plus and TSPOT. The positivity rates of TB1 and TB2 were 5.1% (95%CI 2.5-10.2) and 5.9% (95%CI 3.0-11.2), respectively, with no significant difference. The concordance rate was 99.3% (κ coefficient, 0.93). TB2 did not show a higher positivity rate compared with TB1. The estimated prevalence of LTBI by using the both IGRAs was 3.7-5.9% in renal transplant recipients. These results were equivalent to the IGRAs positivity rate in the general Japanese population, even under the condition of immunosuppressive therapy. In consideration of the higher risk of developing active TB from LTBI, we can use both IGRAs as acceptable tools for LTBI diagnosis in renal transplant recipients.

Infections in Healthcare Workers in Germany-22-Year Time Trends

Health workers (HWs) run an increased risk of infection. The standardised data set of an accident insurer was used to analyse the time trends of infection-related claims and confirmed occupational diseases (ODs) in HWs. The numbers of claims and confirmed claims for different infections were analysed for the years 1996 to 2017. The rate of claims and confirmed ODs were calculated per 100,000 full-time workers. The number of claims was relatively stable over time. However, the rate per 100,000 full-time workers decreased from 25.2 to 15.4. The decrease was most pronounced for hepatitis B and hepatitis C infections, which were the most frequent infections for which claims were made at the start of the period. In 2017, tuberculosis (TB)-related claims were more frequent than those related to blood-borne virus infections. However, the growing number of TB claims does not reflect an increased infection risk, but rather improved methods for the diagnosis of latent TB infection (LTBI). Measures to prevent blood-borne virus infections in HWs were successful in the last 22 years, but attention should be paid to newly emerging infections.

Serial testing of healthcare workers for latent tuberculosis infection and long-term follow up for development of active tuberculosis

Background

Healthcare workers (HCWs) are at high risk of tuberculosis (TB) infection due to occupational exposure. It is important to diagnose TB infections in HCWs to prevent nosocomial transmission, particularly among immunocompromised patients.

Objective

The aim of this study was to analyze the rate of tuberculin skin test (TST) conversion and to assess the incidence of active TB after the latent TB infection screenings in high-risk HCWs.

Methods

This retrospective cohort study involved 458 HCWs in TB-related departments between 2009 and 2013. All HCWs underwent a TST and a chest radiograph annually; an interferon-γ release assay (IGRA) was performed on the TST-converted subjects. TST-converted and IGRA-positive HCWs underwent treatment for latent TB infection.

Results

The TST conversion rate was 30.3% from 2009 to 2011 in two years, 7.4% from 2011 to 2012, and 17.4% from 2012 to 2013. Eleven subjects out of 42 TST converters (26%) were IGRA-positive; two of them developed into active pulmonary TB during the follow-up period.

Conclusions

There was significant discordance between TST conversion and IGRA results in high-risk HCWs, and active TB developed only in TST-converted and IGRA-positive HCWs. Therefore, the combined use of TST and IGRA for periodic monitoring of TB infections in high-risk HCWs may be useful.

Borderline QuantiFERON results and the distinction between specific responses and test variability

BACKGROUND

QuantiFERON (QFT) results near the cut-off are subject to debate. We aimed to investigate which borderline QFT results were due to Mycobacterium tuberculosis (Mtb)-specific responses or to test variability.

METHODS

In a contact investigation, tuberculin skin test (TST), QFT and T-SPOT.TB (T-SPOT) were performed in 785 BCG-unvaccinated contacts. Contacts with a low-negative (<0.15), borderline (0.15-0.35), low-positive (0.35-0.70) or high-positive QFT (≥0.70 IU/mL) were compared with respect to exposure, TST and T-SPOT results. Development of active tuberculosis was assessed.

RESULTS

Borderline QFT results occurred in threefold excess over test variability (p = 0.0027). In contacts with low-negative, borderline or positive QFT results, a positive TST occurred in 24.9%, 62.1% and 91.4% (p < 0.0001) and a positive T-SPOT result in 6.3%, 41.3% and 86.4%, respectively (p < 0.0001). Two-third (20/29) of contacts with a borderline and 14/16 (88%) with a low-positive QFT had a positive TST and/or T-SPOT, indicating probable Mtb-infection. During 12 years of follow-up, seven patients were diagnosed with active tuberculosis, two of whom after a low-positive QFT.

CONCLUSIONS

In this study, most borderline and low-positive QFT results were Mtb-specific, showing the biological significance of a borderline QFT. The clinical relevance, however, will be most distinct in patients who are or will be immunocompromised.

Tuberculosis and viral hepatitis infection in Eastern Europe, Asia, and Latin America: impact of tumor necrosis factor-α inhibitors in clinical practice

Tumor necrosis factor-α (TNF-α) inhibitors are increasingly becoming the standard of care for treating a number of inflammatory diseases. However, treatment with TNF-α inhibitors carries an inherent risk of compromising the immune system, resulting in an increased susceptibility to infections and malignancies. This increased risk of infection is of particular concern in Asia, Eastern Europe, and Latin America where tuberculosis (TB) and viral hepatitis are endemic. In this brief review, we examine the literature and review the impact of TNF-α inhibitors on the incidence and the reactivation of latent disease with respect to TB, hepatitis C infection, and hepatitis B infection. Our findings show that TNF-α inhibitors are generally safe, if used with caution. Patients should be screened prior to the initiation of TNF-α inhibitor treatment and given prophylactic treatment if needed. In addition, patients should be monitored during treatment with TNF-α inhibitors and after treatment has stopped to ensure that infections, if detected, are treated promptly and effectively. Our analysis is consistent with other reports and guidelines.

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.

Prevalence of latent tuberculosis infection among foreign students in Lübeck, Germany tested with QuantiFERON-TB Gold In-Tube and QuantiFERON-TB Gold Plus

BACKGROUND

The tuberculosis (TB) incidence rate in foreign-born individuals has been increasing in Germany in recent years. Foreign students may be an important source of latent tuberculosis infection (LTBI) in low-incidence countries. In Germany, there are no guidelines for LTBI screening of foreign students. The aim of the study was to estimate LTBI prevalence and evaluate associated risk factors among foreign students in Germany. The second purpose of our study was to compare the results of the new generation of QuantiFERON-TB Gold Plus (QFT-Plus) to those of its predecessor QuantiFERON-TB Gold In-Tube (QFT-GIT).

METHODS

This cross-sectional study was conducted between February 2016 and March 2016. Foreign students and young professionals attending the university and higher education institutes in Lübeck, Germany were tested with QFT-Plus and QFT-GIT. Participants filled out a questionnaire for the purpose of LTBI risk assessment and analysis. Variables associated with a positive test result were analyzed using logistic regression.

RESULTS

One hundred thirty four students participated in the study. The overall prevalence as regards positive results from both tests, QFT-Plus and QFT-GIT, was 9.7%, and the prevalence of positive QFT-Plus results was 8.2%. The main independent variables associated with a positive QFT-Plus result were a) being born in a high-incidence country (OR = 6.7, 95% CI: 1.3-34.3) and b) previous contact with a person with active TB (OR = 4.5, 95% CI: 1.1-18.3). Higher age (OR = 2.8, 95% CI: 0.7-11.3) and male gender (OR = 1.6, 95% CI: 0.4-6.7) showed a tendency toward positive QFT-Plus results but this was not statistically significant. Agreement between QFT-Plus and QFT-GIT results was κ = 0.85, p < 0.001.

CONCLUSIONS

The LTBI prevalence among foreign students was about 10%. We recommend implementing a policy whereby all foreign students are screened by means of a questionnaire about LTBI risk factors, so that only students with present risk factors are tested for LTBI. The agreement between the new QFT-Plus and the QFT-GIT (κ = 0.85) was good. QFT-Plus might be used in the same format as its predecessor.

Screening for Tuberculosis in Health Care Workers: Experience in an Italian Teaching Hospital

Health care workers (HCW) are particularly at risk of acquiring tuberculosis (TB), even in countries with low TB incidence. Therefore, TB screening in HCW is a useful prevention strategy in countries with both low and high TB incidence. Tuberculin skin test (TST) is widely used although it suffers of low specificity; on the contrary, the in vitro enzyme immunoassay tests (IGRA) show superior specificity and sensitivity but are more expensive. The present study reports the results of a three-year TB surveillance among HCW in a large teaching hospital in Rome, using TST (by standard Mantoux technique) and IGRA (by QuantiFERON-TB) as first- and second-level screening tests, respectively. Out of 2290 HCW enrolled, 141 (6.1%) had a positive TST; among them, 99 (70.2%) underwent the IGRA and 16 tested positive (16.1%). The frequency of HCW tested positive for TB seems not far from other experiences in low incidence countries. Our results confirm the higher specificity of IGRA, but, due to its higher cost, TST can be considered a good first level screening test, whose positive results should be further confirmed by IGRA before the patients undergo X-ray diagnosis and/or chemotherapy.

Prevalence of tuberculosis infection in healthcare workers of the public hospital network in Medellín, Colombia: a Bayesian approach

A latent tuberculosis infection (LTBI) prevalence survey was conducted using tuberculin skin test (TST) and Quantiferon test (QFT) in 1218 healthcare workers (HCWs) in Medellín, Colombia. In order to improve the prevalence estimates, a latent class model was built using a Bayesian approach with informative priors on the sensitivity and specificity of the TST. The proportion of concordant results (TST+,QFT+) was 41% and the discordant results contributed 27%. The marginal estimate of the prevalence P(LTBI+) was 62·1% [95% credible interval (CrI) 53·0–68·2]. The probability of LTBI+ given positive results for both tests was 99·6% (95% CrI 98·1–99·9). Sensitivity was 88·5 for TST and 74·3 for QFT, and specificity was 87·8 for TST and 97·6 for QFT. A high LTBI prevalence was found in HCWs with time-accumulated exposure in hospitals that lack control plans. In a context of intermediate tuberculosis (TB) incidence it is recommended to use only one test (either QFT or TST) in prevalence surveys or as pre-employment tests. Results will be useful to help implement TB infection control plans in hospitals where HCWs may be repeatedly exposed to unnoticed TB patients, and to inform the design of TB control policies.

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.

Detection of latent tuberculosis infection among migrant farmworkers along the US-Mexico border

Background

Migrant farmworkers are among the highest-risk populations for latent TB infection (LTBI) in the United States with numerous barriers to healthcare access and increased vulnerability to infectious diseases. LTBI is usually diagnosed on the border using the tuberculin skin test (TST). QuantiFERON-TB Gold In-Tube (QFT-GIT) also measures immune response against specific Mycobacterium tuberculosis antigens. The objective of this study is to assess the comparability of TST and QFT-GIT to detect LTBI among migrant farmworkers on the border, as well as to examine the effects of various demographic and clinical factors on test positivity.

Methods

Participants were recruited using mobile clinics on the San Luis US-Mexico border and tested with QFT-GIT and TST. Demographic profiles and clinical histories were collected. Kappa coefficients assessed agreement between TST and QFT-GIT using various assay cutoffs. Logistic regression examined factors associated with positive TST or QFT-GIT results.

Results

Of 109 participants, 59 of 108 (55 %) were either TST (24/71, 34 %) or QFT-GIT (52/106, 50 %) positive. Concordance between TST and QFT-GIT was fair (71 % agreement, ĸ = 0.38, 95 % CI: 0.15, 0.61). Factors associated with LTBI positivity included smoking (OR = 1.26, 95 % CI–1.01–1.58) and diabetes/high blood sugar (OR = 0.70, 95 % CI = 0.51–0.98).

Discussion

Test concordance between the two tests was fair, with numerous discordant results observed. Greater proportion of positives detected using QFT-GIT may help avoid LTBI under-diagnosis. Assessment of LTBI status on the border provides evidence whether QFT-GIT should replace the TST in routine practice, as well as identifies risk factors for LTBI among migrant populations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-1959-3) contains supplementary material, which is available to authorized users.

Using IFN-gamma release assay to confirm tuberculin skin test improves the screening of latent tuberculosis infection in Italian healthcare workers

Background

Healthcare workers (HCWs) represent a tuberculosis (TB) risk group for a wide range of tasks in healthcare, even in countries with low TB incidence, like Italy. Latent Tuberculosis Infection (LTBI) screening programs are an important tool for TB prevention in these setting.

Methods

A retrospective study under a LTBI screening program among HCWs at the Siena University Hospital (Italy), was conducted between September 2011 and July 2015. Tuberculin Skin Test (TST) was used as a first level examination; all TST-positive cases were tested with QuantiFERON-TB Gold In-Tube (QFT-GIT) test, together with a group of TST-negative subjects.

Results

Among the 2136 HCWs screened, 144 (6.7 %) were TST-positive and therefore tested with QFT-GIT, confirming a positive result in 36 cases (25 %). Agreement between two tests was poor (k = 0.092; 95 %, Confidence Interval [CI]- 0.048–0.136, p = 0.002). Among TST-positive cases, discordant results occurred more frequently in BCG vaccinated than unvaccinated HCWs (86.3 %, p < 0.001). The probability of a QFT-GIT-positive result increased according to the TST diameter (p = 0.001). No putative risk factor was associated with LTBI occurrence.

Conclusions

The use of QFT-GIT test as a second step in TST-positive cases offers an appropriate tool for LTBI detection, especially among BCG-vaccinated HCWs.

The use of Mycobacterium tuberculosis HspX and GlcB proteins to identify latent tuberculosis in rheumatoid arthritis patients

Understanding the social conditions and immunological characteristics that allow some human immunodeficiency virus (HIV)-exposed patients to remain uninfected represents an on-going challenge. In this study, the socio-demographic and sexual behaviour characteristics and immune activation profiles of uninfected individuals exposed to HIV-infected partners were investigated. A confidential and detailed questionnaire was administered and venous blood was tested using HIV-1/enzyme immunoassays, plasma HIV-1 RNA levels/bDNA and immunophenotyping/flow cytometry to determine the frequencies of CD4 and CD8 T cells expressing activation markers. The data analysis showed significant differences (p < 0.05) for immune parameters in individuals who were uninfected, albeit exposed to HIV-infected partners, compared with unexposed individuals. In particular, the exposed, uninfected individuals had a higher frequency (median, minimum-maximum) of CD4⁺HLA-DR⁺ (4.2, 1.8-6.1), CD8⁺HLA-DR⁺ (4.6, 0.9-13.7), CD4⁺CD45RO⁺ (27.5, 14.2-46.6), CD4⁺CD45RO⁺CD62L⁺ (46.7, 33.9-67.1), CD8⁺CD45RA⁺HLA-DR⁺ (12.1, 3.4-35.8) and CD8⁺CD45RO⁺HLA-DR⁺ (9.0, 3.2-14.8) cells, a decreased percentage of CD8⁺CD28⁺ cells (11.7, 4.5-24.0) and a lower cell-surface expression of Fcγ-R/CD16 on monocytes (56.5, 22.0-130.0). The plasma HIV-1 RNA levels demonstrated detectable RNA virus loads in 57% of the HIV-1⁺ female partners. These findings demonstrate an activation profile in both CD4 and CD8 peripheral T cells from HIV-1 exposed seronegative individuals of serodiscordant couples from a referral centre in Belo Horizonte, state of Minas Gerais.

The use of Mycobacterium tuberculosis HspX and GlcB proteins to identify latent tuberculosis in rheumatoid arthritis patients

Rheumatoid arthritis (RA) is an autoimmune disease characterised by the destruction of articular cartilage and bone damage. The chronic treatment of RA patients causes a higher susceptibility to infectious diseases such as tuberculosis (TB); one-third of the world’s population is latently infected (LTBI) with Mycobacterium tuberculosis (Mtb). The tuberculin skin test is used to identify individuals LTBI, but many studies have shown that this test is not suitable for RA patients. The goal of this work was to test the specific cellular immune responses to the Mtb malate synthase (GlcB) and heat shock protein X (HspX) antigens of RA patients and to correlate those responses with LTBI status. The T-helper (Th)1, Th17 and Treg-specific immune responses to the GlcB and HspX Mtb antigens were analysed in RA patients candidates for tumour necrosis factor-α blocker treatment. Our results demonstrated that LTBI RA patients had Th1-specific immune responses to GlcB and HspX. Patients were followed up over two years and 14.3% developed active TB. After the development of active TB, RA patients had increased numbers of Th17 and Treg cells, similar to TB patients. These results demonstrate that a GlcB and HspX antigen assay can be used as a diagnostic test to identify LTBI RA patients.

Simulation of risk of tuberculosis infection in healthcare workers in hospitals of an intermediate incidence country

We simulated the frequency of tuberculosis infection in healthcare workers in order to classify the risk of TB transmission for nine hospitals in Medellín, Colombia. We used a risk assessment approach to estimate the average number of infections in three risk groups of a cohort of 1082 workers exposed to potentially infectious patients over 10- and 20-day periods. The risk level of the hospitals was classified according to TB prevalence: two of the hospitals were ranked as being of very high priority, six as high priority and one as low priority. Consistent results were obtained when the simulation was validated in two hospitals by studying 408 healthcare workers using interferon gamma release assays and tuberculin skin testing. The latent infection prevalence using laboratory tests was 41% [95% confidence interval (CI) 34·3-47·7] and 44% (95% CI 36·4-51·0) in those hospitals, and in the simulation, it was 40·7% (95% CI 32·3-49·0) and 36% (95% CI 27·9-44·0), respectively. Simulation of risk may be useful as a tool to classify local and regional hospitals according to their risk of nosocomial TB transmission, and to facilitate the design of hospital infection control plans.

Occupational screening for tuberculosis and the use of a borderline zone for interpretation of the IGRA in German healthcare workers

Introduction

Healthcare workers (HCWs) in low incidence countries with contact to patients with tuberculosis (TB) are considered a high-risk group for latent TB infection (LTBI) and therefore are routinely screened for LTBI. The German Occupational TB Network data is analyzed in order to estimate the prevalence and incidence of LTBI and to evaluate putative risk factors for a positive IGRA and the performance of IGRA in serial testing.

Methods

3,823 HCWs were screened with the Quantiferon Gold in Tube (QFT) at least once; a second QFT was performed on 817 HCWs either in the course of contact tracing or serial examination. Risk factors for a positive QFT were assessed by a questionnaire.

Results

We observed a prevalence of LTBI of 8.3%. Putative risk factors for a positive QFT result were age >55 years (OR 6.89), foreign country of birth (OR 2.39), personal history of TB (OR 6.23) and workplace, e.g. internal medicine (OR 1.40), infection ward (OR 1.8) or geriatric care (OR 1.8). Of those repeatedly tested, 88.2% (721/817) tested consistently QFT-negative and 47 were consistently QFT-positive (5.8%). A conversion was observed in 2.8% (n = 21 of 742 with a negative first QFT) and a reversion occurred in 37.3% (n = 28 of 75 with a positive first QFT). Defining a conversion as an increase of the specific interferon concentration from <0.2 to >0.7 IU/ml, the conversion rate decreased to 1.2% (n = 8). Analogous to this, the reversion rate decreased to 18.8% (n = 9).

Discussion

In countries with a low incidence of TB and high hygiene standards, the LTBI infection risk for HCWs seems low. Introducing a borderline zone from 0.2 to ≤0.7 IU/ml may help to avoid unnecessary X-rays and preventive chemotherapy. No case of active TB was detected. Therefore, it might be reasonable to further restrict TB screening to HCWs who had unprotected contact with infectious patients or materials.

Cost-effectiveness of interferon-gamma release assay for systematic tuberculosis screening of healthcare workers in low-incidence countries

BACKGROUND

Tuberculosis (TB) is one of the important occupationally acquired infectious diseases in low-incidence countries. Delays in TB diagnosis and treatment among healthcare workers (HCWs) result in costly large-scale TB contact screening among patients and other HCWs.

AIM

To assess the cost-effectiveness of TB screening for HCWs using interferon-gamma release assays (IGRAs) compared with tuberculin skin test (TST) and chest x ray (CXR).

METHODS

Markov models were constructed using a hospital payer perspective. The target populations were a hypothetical cohort of 30-year-old HCWs at the time of employment, and a hypothetical cohort of HCWs working on a high-risk ward until 60 years of age. Six strategies were modelled: TST, QuantiFERON-TB Gold In-Tube (QFT), T-SPOT.TB (T-SPOT), TST followed by QFT, TST followed by T-SPOT, and CXR. The main outcome measure of effectiveness was quality-adjusted life-years (QALYs). Costs and QALYs gained per person screened were calculated.

FINDINGS

QFT was the most cost-effective strategy at the 'willingness to pay' level of US$ 50,000/QALYs gained (at the time of employment: US$ 334.91, 21.071 QALYs; on a high-risk ward: US$ 1050.32, 20.968 QALYs; values for 2012). Cost-effectiveness was sensitive to latent TB infection (LTBI) rate and bacillus Calmette-Guérin vaccination rate. TST followed by QFT was more cost-effective than QFT when the LTBI rate was <0.026 at the time of employment and <0.08 on a high-risk ward.

CONCLUSION

Systematic TB screening using QFT is cost-effective for screening HCWs, and is recommended in low-incidence countries.

Vitamin D status and incidence of tuberculosis infection conversion in contacts of pulmonary tuberculosis patients: a prospective cohort study

The objective of this study was to estimate the relationship between serum vitamin D (VitD) status and tuberculosis (TB) infection conversion (TBIC), measured by the tuberculin skin test (TST) and an interferon-gamma release assay, the QuantiFERON-TB Gold In-Tube (QFT-GIT) test, in the contacts of pulmonary TB patients in Castellon (Spain) in a prospective cohort study from 2010 to 2012. Initially, the participants were negative to latent TB infection after a screening that included TST and QFT-GIT tests, and other examinations. A baseline determination of 25-hydroxyvitamin D [25(OH)D] was obtained by chemiluminescence immunoassay. After 8-10 weeks, participants were screened for a second time to determine TB infection conversion (TBIC). Poisson regression models were used in the statistical analysis. Of the 247 participants in the cohort, 198 (80·2%) were screened twice and 18 (9·1%) were TBIC cases. The means of VitD concentration in the TBIC cases and the non-cases were 20·7±11·9 and 27·2±11·4 ng/ml (P = 0·028), respectively. Adjusted for high exposure and TB sputum acid-fast bacilli (AFB)-positive index case, higher serum VitD concentration was associated with low incidence of TBIC (P trend = 0·005), and an increase of 1 ng/ml VitD concentration decreased the incidence of TBIC by 6% (relative risk 0·94, 95% confidence interval 0·90-0·99, P = 0·015). The results suggest that sufficient VitD level could be a protective factor of TBIC.

Tuberculosis screening at the Sainte-Anne Hospital in Paris - results of first and second IGRA

INTRODUCTION

Healthcare workers (HCWs) are exposed to Mycobacterium tuberculosis (MTB) and therefore are screened for tuberculosis (TB). Results of TB screenings with the Interferon-γ Release Assay (IGRA) in a French psychiatric hospital without a TB ward are described.

METHODS

At the Sainte-Anne Hospital, a referral centre for psychiatric patients throughout the municipal region of Paris, IGRA screening is performed during pre-employment and general health examination or after potential contact to MTB. The QuantiFERON Gold in tube (QFT) is used and data on TB history are assessed in a standardized manner.

RESULTS

Between August 2008 und August 2013 in total 1.192 HCWs were tested and the QFT was positive in 265 (22.2%). Probability of a positive QFT increased with age. A second QFT was performed in 144 HCWs with a positive QFT and 53 (36.8%) HCWs had a reversion. With a positive QFT close to the cut-off (e.g. 0.35-0.7 IU/ml) the odds ratio for a reversion was 4.6 compared to an INF-γ concentration of ≥3.0 IU/ml. Probability of reversion was not influenced by preventive chemotherapy, which was completed by 28 (19.4%) HCWs with a positive QFT. No active TB was detected.

CONCLUSION

Prevalence of positive IGRA is high in French HCWs as is the number of reversions in IGRA. Reversion rate is particularly high around the cut-off of the IGRA. A borderline zone will therefore reduce the influence of test variability.

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.

Tuberculosis in healthcare workers - a narrative review from a German perspective

Introduction

Despite the decline of tuberculosis in the population at large, healthcare workers (HCW) are still at risk of infection.

Methods

In a narrative review the TB risk in HCW and preventive measures are described, with the focus on epidemiology and Occupational Safety and Health (OSH) regulations in Germany.

Results

There is an increased risk of infection not only in pneumology and laboratories with regular contact with tuberculosis patients or infectious materials. Epidemiological studies have also verified an increased risk of infection from activities that involve close contact with patients’ breath (e.g. bronchoscopy, intubation) or close contact with patients in need of care in geriatric medicine or geriatric nursing. In occupational disease claim proceedings on account of tuberculosis, the burden of proof can be eased for insured persons who work in these or other comparable fields. Forgoing evidence of an index person as a source of infection has led to a doubling of the rate of cases of tuberculosis recognised as an occupational disease and has halved the duration of occupational disease claim proceedings in Germany. For several years now, it has been possible to use the new interferon-y release assays (IGRAs) to diagnose a latent tuberculosis infection (LTBI) with significantly greater validity than with the traditional tuberculin skin test (TST). However, variability of the IGRAs around the cut-off poses problems especially in serial testing of HCWs. At around 10%, LTBI prevalence in German healthcare workers is lower than had been assumed. It can make sense to treat a recent LTBI in a young healthcare worker so as to prevent progression into active tuberculosis. If the LTBI is occupational in origin, the provider of statutory accident insurance can cover the costs of preventive treatment. However, little is known about disease progression in HCWs with positive IGRA sofar.

Conclusion

TB screening in HCWs will remain an important issue in the near future even in low incidence, high income countries, as active TB in HCWs is often due to workplace exposure. The IGRAs facilitate these screenings. However, variability of IGRA results in serial testing of HCWs need further investigations.

Interferon-γ release assays and tuberculin skin testing for diagnosis of latent tuberculosis infection in healthcare workers in the United States

RATIONALE

IFN-γ release assays (IGRAs) are alternatives to tuberculin skin testing (TST) for diagnosis of latent tuberculosis infection. Limited data suggest IGRAs may not perform well for serial testing of healthcare workers (HCWs).

OBJECTIVES

Determine the performance characteristics of IGRAs versus TST for serial testing of HCWs.

METHODS

A longitudinal study involving 2,563 HCWs undergoing occupational tuberculosis screening at four healthcare institutions in the United States, where the average tuberculosis case rate ranged from 4 to 9 per 100,000 persons. QuantiFERON-TB Gold In-Tube (QFT-GIT), T-SPOT.TB (T-SPOT), and TST were performed at baseline and every 6 months for 18 months between February 2008 and March 2011.

MEASUREMENTS AND MAIN RESULTS

A total of 2,418 HCWs completed baseline testing, which was positive for 125 (5.2%) by TST, 118 (4.9%) by QFT-GIT, and 144 (6.0%) by T-SPOT. A baseline positive TST with negative IGRAs was associated with bacillus Calmette-Guérin (BCG) vaccination (odds ratio: 25.1 [95% confidence interval: 15.5, 40.5] vs. no BCG). Proportions of participants with test conversion during the study period were 138 of 2,263 (6.1%) for QFT-GIT, 177 of 2,137 (8.3%) for T-SPOT, and 21 of 2,293 (0.9%) for TST (P < 0.001 for QFT-GIT vs. TST and for T-SPOT vs. TST; P = 0.005 for QFT-GIT vs. T-SPOT). Of the QFT-GIT and T-SPOT converters, 81 of 106 (76.4%) and 91 of 118 (77.1%), respectively, were negative when retested 6 months later. There was negative/positive discordance for 15 of 170 (8.8%) participants by QFT-GIT and for 19 of 151 (12.6%) by T-SPOT when blood was drawn 2 weeks later.

CONCLUSIONS

Most conversions among HCWs in low TB incidence settings appear to be false positives, and these occurred six to nine times more frequently with IGRAs than TST; repeat testing of apparent converters is warranted.

The effect of introducing IGRA to screen French healthcare workers for tuberculosis and potential conclusions for the work organisation

INTRODUCTION

In France, pre-employment screening for tuberculosis (TB) is performed for healthcare workers (HCW). Screening is repeated when exposure to TB patients or infectious material occurs. The results of these TB screenings were analysed in a retrospective analysis.

METHOD

Tuberculin skin tests (TST) and interferon-gamma release assays (QuantiFERON® Gold In-Tube - QFT) were used to perform the TB screenings. The screening results of 637 HCWs on whom QFT was performed were taken from the records of the University Hospital of Nantes.

RESULTS

In three (0.5%) HCW, the QFT was indeterminate. In 22.2%, the QFT was positive. A second QFT was performed in 118 HCWs. The reversion rate was 42% (5 out of 17). The conversion rate was 6% (6 out of 98). A TST was performed on 466 (73.5%) of the HCWs. Results for TST > 10 mm were 77.4%. In those with a TST < 10 mm, QFT was positive in 14% and in those with a TST ≥ 10 mm, QFT was positive in 26.7%. Depending on the definition for conversion in the QFT, the annual attack rate was 4.1% or 7.3%. X-ray and pneumology consultation was based on positive QFT rather than TST alone (52 out of 56). No active TB was detected.

CONCLUSION

The TST overestimated the prevalence of LTBI in this cohort. The decision about X-ray and consultation regarding preventive treatment should be based on the QFT rather than the TST results. The high reversion rate should be taken into consideration when consulting with HCWs regarding preventive treatment. The high conversion rate seems to indicate that preventive measures such as wearing masks should be improved.

Screening for tuberculosis and the use of a borderline zone for the interpretation of the interferon-γ release assay (IGRA) in Portuguese healthcare workers

Introduction

The effect of using a borderline zone for the interpretation of the interferon-γ release assay (IGRA) on the prediction of progression to active tuberculosis (TB) in healthcare workers (HCW) is analysed.

Methods

Data from a published study on TB screening in Portuguese HCW is reanalysed using a borderline zone for the interpretation of the IGRA. Testing was performed with the QuantiFERON-TB Gold In-Tube (QFT). The borderline zone for the QFT was defined as interferon (INF) in QFT ≥0.2 to <0.7 IU/mL. An X-ray was performed when the IGRA was positive (≥0.35 IU/mL) or typical symptoms were present. Sputum analysis was performed according to the X-ray or the presence of typical symptoms.

Results

The cohort comprised 2,884 HCW with a QFT that could be interpreted. In 1,780 (61.7%) HCW, the QFT was <0.2 IU/mL. A borderline result was found in 341 (11.8%) and a QFT >0.7 IU/mL in 763 (26.3%) HCW. Fifty-seven HCW had a TB in their medical history, eight had a TB at the time of screening and progression to active TB was observed in four HCW. Two out of eight HCW (25%) with active TB at the time of screening had a QFT result falling into the borderline zone. One out of four HCW (25%) who progressed towards active TB after being tested with QFT had QFT results falling into the borderline zone. A second IGRA was performed in 1,199 HCW. In total, 292 (24.4%) HCW had at least one of the two IGRA results pertaining to the borderline zone.

Conclusion

Using a borderline zone for the QFT from 0.2 to 0.7 IU/mL should be administered with care, as active TB as well as progression to active TB might be overlooked. Therefore, the borderline zone should be restricted to populations with a low TB risk only.