Performance of Screening Strategies for Latent Tuberculosis Infection in Patients with Inflammatory Bowel Disease: Results from the ENEIDA Registry of GETECCU

(1) Aims: Patients receiving antitumor necrosis factor (anti-TNF) therapy are at risk of developing tuberculosis (TB), usually due to the reactivation of a latent TB infection (LTBI). LTBI screening and treatment decreases the risk of TB. This study evaluated the diagnostic performance of different LTBI screening strategies in patients with inflammatory bowel disease (IBD). (2) Methods: Patients in the Spanish ENEIDA registry with IBD screened for LTBI between January 2003 and January 2018 were included. The diagnostic yield of different strategies (dual screening with tuberculin skin test [TST] and interferon-ץ-release assay [IGRA], two-step TST, and early screening performed at least 12 months before starting biological treatment) was analyzed. (3) Results: Out of 7594 screened patients, 1445 (19%; 95% CI 18−20%) had LTBI. Immunomodulator (IMM) treatment at screening decreased the probability of detecting LTBI (20% vs. 17%, p = 0.001). Regarding screening strategies, LTBI was more frequently diagnosed by dual screening than by a single screening strategy (IGRA, OR 0.60; 95% CI 0.50−0.73, p < 0.001; TST, OR 0.76; 95% CI 0.66−0.88, p < 0.001). Two-step TST increased the diagnostic yield of a single TST by 24%. More cases of LTBI were diagnosed by early screening than by routine screening before starting anti-TNF agents (21% [95% CI 20−22%] vs. 14% [95% CI 13−16%], p < 0.001). The highest diagnostic performance for LTBI (29%) was obtained by combining early and TST/IGRA dual screening strategies in patients without IMM. (4): Conclusions: Both early screening and TST/IGRA dual screening strategies significantly increased diagnostic performance for LTBI in patients with IBD, with optimal performance achieved when they are used together in the absence of IMM.

Prevalence and risk factors for latent tuberculosis among diabetes patients in Taiwan: A cross-sectional study

INTRODUCTION

Diabetes mellitus (DM) is a known risk factor for tuberculosis (TB), leading to an approximate three-fold higher risk of developing active TB. However, epidemiological studies on the prevalence of latent TB infection (LTBI) in DM patients are lacking. In this study, we investigated the presence of LTBI and determined risk factors for LTBI in DM patients.

METHODOLOGY

We conducted a cross-sectional study at Taipei Medical University-Shuang Ho Hospital in northern Taiwan. The study population comprised DM patients (aged 20-70 years) attending a metabolism outpatient clinic between February 2011 and February 2013, excluding patients who were suspected or confirmed to have active TB. Venous blood samples were drawn from patients to detect LTBI using the QuantiFERON-TB Gold In-Tube (QFT-GIT) method.

RESULTS

We enrolled 1120 patients with DM. The QFT-GIT showed positive results for 241 people (21.5%) and negative results for 879 people (78.5%). The mean age at QFT-GIT positivity was 58.2 years, which was significantly dissimilar to the mean age at QFT-GIT negativity, which was 55.0 years (p < 0.001). Multivariate logistic regression indicated that the trend of QFT-GIT positivity increased after the age of 50 years. Effective glycemic control did not differ significantly between QFT-GIT-positive and -negative patients. Moreover, men were predominant were predominant in both QFT-GIT-positive and -negative patients.

CONCLUSIONS

More than one-fifth of DM patients have LTBI. Among the DM patients, those older than 50 years may have a higher risk of LTBI. Moreover, effective glycemic control did not differ significantly in patients with LTBI.

Impact of T-Cell Xtend on T-SPOT.TB Assay in High-Risk Individuals after Delayed Blood Sample Processing

T-SPOT.TB (T-SPOT) is an interferon gamma release assay (IGRA) used to detect infection with Mycobacterium tuberculosis based on the number of spot-forming T cells; however, delays in sample processing have been shown to reduce the number of these spots that are detected following laboratory processing. Adding T-Cell Xtend (XT) into blood samples before processing reportedly extends the amount of time allowed between blood collection and processing up to 32 h. In this study, paired blood samples from 306 adolescents and adults at high risk for latent tuberculosis (TB) infection (LTBI) or progression to TB disease were divided into three groups: (i) early processing (∼4.5 h after collection) with and without XT, (ii) delayed processing (∼24 h after collection) with and without XT, and (iii) early processing without XT and delayed processing with XT. The participants' paired samples were processed at a local laboratory and agreement of qualitative and quantitative results was assessed. The addition of XT did not consistently increase or decrease the number of spots. In groups 1, 2, and 3, samples processed with XT had 13% (10/77), 28.0% (30/107), and 24.6% (30/122), respectively, more spots, while 33.8% (26/77), 26.2% (28/107), and 38.5% (47/122) had fewer spots than samples processed without XT. The findings suggest that XT does not reliably mitigate the loss of spot-forming T cells in samples with processing delay.

[Concordance between the test of the tuberculin and Interferon Gamma Release Assay-IGRA in patients with immune-mediated inflammatory diseases]

OBJECTIVE

The immunosuppressive therapies in the treatment of the immune-mediated inflammatory diseases (EIMI) predispose individuals to the tuberculosis, so the screening of latent tuberculosis infection (ITL) and the treatment reduces the likelihood of a progression to an active tuberculosis. The aim of the study was to analyze the concordance between the test of the tuberculin (PT) and "Interferon Gamma Release Assay-IGRA" in relation to the type of EIMI and the immunosuppressive treatment (IS).

METHODS

Transversal study of patients with EIMI candidates or in treatment IS forwarded to the ITL screening, from April 2017 until May 2018. The outcome variables were PT and IGRA. The explicative variables were: EIMI, IS, age, gender, prior BCG vaccination and tuberculosis risk factors.

RESULTS

A total of 146 patients were analyzed (33[22.6%] vaccinated with BCG, 1 [0.7%] with a pre-diagnosis of tuberculosis, and 22 [15.1%] from an endemic country). Kappa index (k) was 0,338 between PT and IGRA for the whole sample. A lower concordance was found in patients with the Crohn's disease (k=0.125), in the ones treated with corticosteroids (k=0.222), vaccinated with BCG (k=0.122) and in patients from tuberculosis endemic countries (k=0.128).

CONCLUSIONS

The concordance between PT and IGRA is affected in patients with EIMI, and to a greater extent to patients with the inflammatory bowel disease, with the corticotherapy, with the BCG vaccination, or in the ones from endemic countries.

The performance of T-cell Xtend reagent in increasing blood storage times for interferon gamma release assays

BACKGROUND

T-cell Xtend (TCX) was introduced to extend the blood storage time for T-SPOT.TB test, a widely used commercial interferon gamma release assay (IGRA) for rapid in vitro tuberculosis.

METHODS

A total of 99 Uyghur suspected tuberculosis patients were recruited in this study. T-SPOT.TB test was performed with fresh blood (controls), 36 hours delayed blood and delayed and TCX-treated (at 36 hours) blood from each patient, respectively.

RESULTS

White blood cells and lymphocytes proportion in peripheral blood mononuclear cells s and spot-forming cells in positive control wells decreased significantly in delayed blood samples when compared with controls, while this decrease was not detected in TCX-treated group. In the 58 patients with paired T-SPOT.TB results of three groups of samples, a higher positive rate was observed in TCX-treated group than both in controls and untreated group (41.4% vs 37.9% and 25.9%). The concordance of T-SPOT.TB results between the treated group and controls was 0.856, whereas the agreement between controls and untreated group was unsatisfactory (0.649). In the 23 elderly patients (>70 years old) with paired T-SPOT.TB results of controls and TCX group, treated group showed a non-significant trend toward higher positive rate than controls (43.5% vs 26.1%, P=.22). Meanwhile, TCX treatment reduced the risk of false negative T-SPOT.TB results in the elderly population.

CONCLUSION

Deterioration of blood sample caused by long storage time can be neutralized by TCX treatment. The results provide data for the utility of TCX in a novel population and in Asian region, and reveal the potential of TCX to improve the accuracy of T-SPOT.TB test in elderly population.

Methods Used in Economic Evaluations of Tuberculin Skin Tests and Interferon Gamma Release Assays for the Screening of Latent Tuberculosis Infection: A Systematic Review

BACKGROUND

Latent tuberculosis infection (LTBI) provides a constant pool of new active tuberculosis cases; a third of the earth's population is estimated to be infected with LTBI.

OBJECTIVE

The objective of this systematic review was to assess the quality and summarize the available evidence from published economic evaluations reporting on the cost-effectiveness of tuberculin skin tests (TSTs) compared with interferon gamma release assays (IGRAs) for the screening of LTBI.

METHODS

An extensive systematic review of the published literature was conducted. A two-step process was adopted to identify relevant articles: information was extracted into evidence tables and then analyzed. The quality of the publications was assessed using a 10-item checklist specific for economic evaluations.

RESULTS

Twenty-eight studies were identified for inclusion in this review. Most of the studies found IGRAs to be more cost-effective than TSTs; however, the conclusions from the studies varied significantly. Most studies scored highly on the checklist although only one fulfilled all the stipulated criteria. A wide variety of methodological approaches were documented; identified differences included the type of economic evaluation and model, time horizon, perspective, and outcomes measures.

CONCLUSIONS

The lack of consistent methods across studies makes it difficult to draw any firm conclusions about the most cost-effective option between TSTs and IGRAs. This problem can be solved by improving the quality of economic evaluation studies in the field of LTBI screening, through adherence to quality checklists.

Major Loci on Chromosomes 8q and 3q Control Interferon γ Production Triggered by Bacillus Calmette-Guerin and 6-kDa Early Secretory Antigen Target, Respectively, in Various Populations

Background. Interferon γ (IFN-γ) release assays (IGRAs) provide an in vitro measurement of antimycobacterial immunity that is widely used as a test for Mycobacterium tuberculosis infection. IGRA outcomes are highly heritable in various populations, but the nature of the involved genetic factors remains unknown.

Methods. We conducted a genome-wide linkage analysis of IGRA phenotypes in families from a tuberculosis household contact study in France and a replication study in families from South Africa to confirm the loci identified.

Results. We identified a major locus on chromosome 8q controlling IFN-γ production in response to stimulation with live bacillus Calmette-Guerin (BCG; LOD score, 3.81; P = 1.40 × 10⁻⁵). We also detected a second locus, on chromosome 3q, that controlled IFN-γ levels in response to stimulation with 6-kDa early secretory antigen target, when accounting for the IFN-γ production shared with that induced by BCG (LOD score, 3.72; P = 1.8 × 10⁻⁵). Both loci were replicated in South African families, where tuberculosis is hyperendemic. These loci differ from those previously identified as controlling the response to the tuberculin skin test (TST1 and TST2) and the production of TNF-α (TNF1).

Conclusions. The identification of 2 new linkage signals in populations of various ethnic origins living in different M. tuberculosis exposure settings provides new clues about the genetic control of human antimycobacterial immunity.