Interferon-γ release assay in the diagnosis of latent tuberculosis infection in arthritis patients treated with tumor necrosis factor antagonists in Korea

Epidemiology of Latent Tuberculosis in Rheumatic Immune-Mediated Inflammatory Diseases-Study of 1117 Patients and Descriptive Literature Review

Background/Objectives: Patients with rheumatic immune-mediated diseases (rheumatic-IMID) and latent tuberculosis (LTBI) are at an increased risk of developing active tuberculosis (TB); therefore, screening is recommended before starting biological treatment. The aims of this study were as follows: (i) to assess the prevalence of LTBI, (ii) to determine the importance of using a booster test in TST-negative patients, (iii) to compare the tuberculin skin test (TST) with the interferon-gamma release assay (IGRA), (iv) to perform a review of the prevalence of LTBI. Methods: A cross-sectional hospital study was performed, including patients diagnosed with rheumatic-IMID who underwent a TST and/or IGRA during the period 2016-2020. If the first TST was negative, a new TST (booster) was performed. Results: A total of 1117 patients were included. The overall prevalence of LTBI was estimated to be 31.7% (95% confidence interval, 29.74-33.66). The LTBI prevalence ranged from 38.5% for vasculitis to 14% for sarcoidosis. The booster test was positive in 22.9% of 817 patients with a negative or indeterminate IGRA. The IGRA was positive in 3.8% of 793 patients with a negative booster.The adjusted Cohen's kappa coefficient between TST (+booster) and IGRA was 0.62. Conclusions: LTBI is frequent in patients with rheumatic-IMID. IGRA and TST (+booster) show a moderate, fair grade of agreement. Therefore, performing both tests before biological therapy should be highly recommended.

Reactivation of latent tuberculosis with TNF inhibitors: critical role of the beta 2 chain of the IL-12 receptor

Tumor necrosis factor (TNF) inhibitors have improved a lot the treatment of numerous diseases, with the well-known example of rheumatoid arthritis (RA). In the early 2000s, postmarketing data quickly revealed an alarming number of severe tuberculosis (TB) under such treatment. These findings were consistent with previous results in mice where TNF is essential for lymph node formation and granuloma organization. The effects of TNF inhibition on RA synovium structure are very similar to those on granuloma, with changes in cellular interactions, cytokine, and chemokine production. In addition to the role of TNF in granuloma, the interleukin (IL)-12/interferon (IFN)-γ pathway is required for an efficient host defense against TB. Primary and secondary immunodeficiencies affecting this pathway lead to severe bacillus Calmette-Guérin (BCG) reaction or full TB. Any chronic inflammation as in RA induces a systemic Th1 defect that predisposes to TB through specific downregulation of the IL-12Rß2 chain. When TNF inhibitors are initiated, this transiently increases this risk of TB, through effects on cellular interactions in a latent TB granuloma. At a later stage, when a better control disease activity is obtained, the risk of TB is reduced but not abrogated. Given the clear benefit from TNF inhibition, latent TB infection screening at baseline is essential for an optimal safety.

Assessment of latent infections in patients receiving biological therapies

The use of biological (or targeted) therapies constitutes a major advance in the management of autoinflammatory and malignant diseases. However, due to the selective effect of these agents on the host's immune response, reactivation of certain pathogens that cause latent infection is to be expected. The most relevant concern is the risk of reactivation of latent tuberculosis infection (LTBI) and progression to active tuberculosis among patients treated with agents targeting tumor necrosis factor (TNF)-α. Systematic screening for LTBI at base-line with appropriate initiation of antituberculous treatment, if needed, is mandatory in this patient population as risk minimization strategy. In addition, reactivation of hepatitis B virus induced by B-cell-depleting (anti-CD20) and anti-TNF-α agents should be also prevented among HBsAg-positive patients and those with isolated anti-HBc IgG positivity (risk of "occult HBV infection"). The present review summarizes available evidence regarding the risk of reactivation of these latent infections induced by newer biological agents, as well as the recommendations included in the most recent guidelines.

Risk of infection associated with anti-TNF-α therapy

INTRODUCTION

The advent, more than two decades ago, of monoclonal antibodies and soluble receptors targeting tumor necrosis factor (TNF)-α has revolutionized the therapeutic approach to otherwise difficult-to-treat autoimmune and inflammatory diseases. However, due to the pleiotropic functions played by this pro-inflammatory cytokine (with particular relevance in granuloma maintenance), TNF-α blockade may increase the incidence of serious infections. Areas covered: The present review summarizes the biological rationale supporting the impact of anti-TNF-α therapy on the host's susceptibility to infection. The structure, mode of action, and indications of available agents are reviewed, as well as the clinical evidence coming from clinical trials and observational registries. We discuss the impact of patient- and disease-related factors influencing the occurrence of infection. Finally, strategies for risk minimization are also covered, with particular attention to recommendations for screening of latent tuberculosis infection and management of chronic hepatitis B infection. Expert commentary: Methodological limitations (confounding by indication bias, patient dropout, or switching therapies) should be considered when interpreting observational data. Clinicians must individualize the infection risk assessment not only on the basis of the specific anti-TNF-α agent used or the expected duration of therapy, but also by taking into account the baseline susceptibility of a given patient.

Systemic review: agreement between the latent tuberculosis screening tests among patients with rheumatic diseases

BACKGROUND/AIMS

To estimate the level of agreement and positivity rates of latent tuberculosis infection (LTBI) tests prior to the use of tumor necrosis factor (TNF) inhibitors in relation to underlying rheumatic diseases and endemic tuberculosis levels.

METHODS

The Ovid-Medline, Embase, and Cochrane Libraries were searched for articles before October 2013 involving LTBI screening in rheumatic patients, including rheumatoid arthritis (RA), ankylosing spondylitis (AS), juvenile idiopathic arthritis (JIA), and psoriatic arthritis.

RESULTS

In pooled analyses, 5,224 rheumatic patients had undergone both a tuberculin skin test (TST) and an interferon-gamma release assay (IGRA) before TNF inhibitors use. The positivity of TST, QuantiFERON-TB Gold In Tube (QFT-GIT), and T-SPOT.TB (T-SPOT) tests were estimated to be 29%, 17%, and 18%, respectively. The agreement percentage between the TST and QFT-GIT, and between the TST and T-SPOT were 73% and 75%. Populations from low-to-moderate endemic TB presented with slightly less agreement (71% between TST and QFT-GIT, and 74% between TST and T-SPOT) than patients from high endemic countries (73% between TST and QFT-GIT, and 81% between TST and T-SPOT). By underlying disease stratification, a lower level of agreement between TST and QFT-GIT was found among AS (64%) than among JIA (77%) and RA patients (73%).

CONCLUSION

We reaffirm the current evidence for accuracy of LTBI test done by TST and IGRA among rheumatic patients is inconsistent. Our stratified analysis suggests different screening strategies might be needed in clinical settings considering the endemic status in the patient's country of origin and the precise nature of underlying diseases.

Comparative Evaluation of QuantiFERON-TB Gold In-Tube and QuantiFERON-TB Gold Plus in Diagnosis of Latent Tuberculosis Infection in Immunocompromised Patients

QuantiFERON-TB Gold Plus (QFT-Plus) is a new-generation QuantiFERON-TB Gold In-Tube (QFT-GIT) assay which has two antigen-coated tubes called TB1, which contains long peptides derived from ESAT-6 and CFP-10, and TB2, which contains the same components as TB1 and additional short peptides which potentially stimulate CD8⁺ T cells through the presentation of major histocompatibility complex class I. This is the first study to compare QFT-Plus and QFT-GIT for use in the diagnosis of latent tuberculosis infection (LTBI) among immunocompromised patients in the Republic of Korea. Among 317 consecutive patients who underwent screening for LTBI before solid organ or hematopoietic stem cell transplantation and tumor necrosis factor alpha inhibitor treatment, LTBI was identified in 92 (29.0%) and 88 (27.8%) patients by QFT-GIT and QFT-Plus, respectively. The rate of concordance between QFT-GIT and QFT-Plus was 93.7% (κ value, 0.860), and the indeterminate rate (3.2%) was similar between QFT-GIT and QFT-Plus. Of 20 (6.3%) samples with discordant results, 11 (55.0%) and 7 (35.0%) were positive by QFT-GIT alone and QFT-Plus alone, respectively, and 2 (15.0%) were indeterminate by each assay. The interferon gamma level in samples with discordant results ranged from 0.39 to 1.10 IU/ml, except for one sample, in which the gamma interferon level was 2.97 IU/ml only in TB2. Conclusively, there was a high degree of agreement between the results of QFT-GIT and QFT-Plus for the screening of immunocompromised patients for LTBI. The reactivity in TB2 contributed substantially to the difference between QFT-GIT and QFT-Plus, particularly in solid organ transplant candidates. The significance of the discrete responses in TB1 and TB2 of QFT-Plus needs to be explored further by means of an immunological and clinical approach in different patient groups and clinical settings.

Tuberculosis associated with tumor necrosis factor-α antagonists, case description and analysis of reported cases in Colombia

Tumor necrosis factor-α (TNF-α) is an important fundamental cytokine during the immune response against cancer and infections such as tuberculosis. This molecule also plays a key pathogenic role in complex and difficult-to-treat diseases such as rheumatoid arthritis, ankylosing spondylitis, Crohn's disease, psoriasis and ulcerative colitis. The treatment of these diseases frequently needs TNF-α antagonists, which has been related to an increased risk of developing tuberculosis, mycoses, and other severe infections.We report the case of a 68-year-old man with Crohn's disease, who developed  disseminated tuberculosis due to anti-TNF-α immunosuppressive therapy. The diagnosis was based on the histopathological findings and molecular biology assays.We discuss the clinical presentation and workup of this case, and we present a comparative analysis of tuberculosis cases associated with anti-TNF-α reported in Colombia during the last 10 years emphasizing on the diagnosis and treatment of latent tuberculosis.

Accurate diagnosis of latent tuberculosis in children, people who are immunocompromised or at risk from immunosuppression and recent arrivals from countries with a high incidence of tuberculosis: systematic review and economic evaluation

BACKGROUND

Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB) [(Zopf 1883) Lehmann and Neumann 1896], is a major cause of morbidity and mortality. Nearly one-third of the world's population is infected with MTB; TB has an annual incidence of 9 million new cases and each year causes 2 million deaths worldwide.

OBJECTIVES

To investigate the clinical effectiveness and cost-effectiveness of screening tests [interferon-gamma release assays (IGRAs) and tuberculin skin tests (TSTs)] in latent tuberculosis infection (LTBI) diagnosis to support National Institute for Health and Care Excellence (NICE) guideline development for three population groups: children, immunocompromised people and those who have recently arrived in the UK from high-incidence countries. All of these groups are at higher risk of progression from LTBI to active TB.

DATA SOURCES

Electronic databases including MEDLINE, EMBASE, The Cochrane Library and Current Controlled Trials were searched from December 2009 up to December 2014.

REVIEW METHODS

English-language studies evaluating the comparative effectiveness of commercially available tests used for identifying LTBI in children, immunocompromised people and recent arrivals to the UK were eligible. Interventions were IGRAs [QuantiFERON(®)-TB Gold (QFT-G), QuantiFERON(®)-TB Gold-In-Tube (QFT-GIT) (Cellestis/Qiagen, Carnegie, VA, Australia) and T-SPOT.TB (Oxford Immunotec, Abingdon, UK)]. The comparator was TST 5 mm or 10 mm alone or with an IGRA. Two independent reviewers screened all identified records and undertook a quality assessment and data synthesis. A de novo model, structured in two stages, was developed to compare the cost-effectiveness of diagnostic strategies.

RESULTS

In total, 6687 records were screened, of which 53 unique studies were included (a further 37 studies were identified from a previous NICE guideline). The majority of the included studies compared the strength of association for the QFT-GIT/G IGRA with the TST (5 mm or 10 mm) in relation to the incidence of active TB or previous TB exposure. Ten studies reported evidence on decision-analytic models to determine the cost-effectiveness of IGRAs compared with the TST for LTBI diagnosis. In children, TST (≥ 5 mm) negative followed by QFT-GIT was the most cost-effective strategy, with an incremental cost-effectiveness ratio (ICER) of £18,900 per quality-adjusted life-year (QALY) gained. In immunocompromised people, QFT-GIT negative followed by the TST (≥ 5 mm) was the most cost-effective strategy, with an ICER of approximately £18,700 per QALY gained. In those recently arrived from high TB incidence countries, the TST (≥ 5 mm) alone was less costly and more effective than TST (≥ 5 mm) positive followed by QFT-GIT or T-SPOT.TB or QFT-GIT alone.

LIMITATIONS

The limitations and scarcity of the evidence, variation in the exposure-based definitions of LTBI and heterogeneity in IGRA performance relative to TST limit the applicability of the review findings.

CONCLUSIONS

Given the current evidence, TST (≥ 5 mm) negative followed by QFT-GIT for children, QFT-GIT negative followed by TST (≥ 5 mm) for the immunocompromised population and TST (≥ 5 mm) for recent arrivals were the most cost-effective strategies for diagnosing LTBI that progresses to active TB. These results should be interpreted with caution given the limitations identified. The evidence available is limited and more high-quality research in this area is needed including studies on the inconsistent performance of tests in high-compared with low-incidence TB settings; the prospective assessment of progression to active TB for those at high risk; the relative benefits of two-compared with one-step testing with different tests; and improved classification of people at high and low risk for LTBI.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42014009033.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Concordance between the tuberculin skin test and interferon gamma release assay (IGRA) for diagnosing latent tuberculosis infection in patients with systemic lupus erythematosus and patient characteristics associated with an indeterminate IGRA

OBJECTIVE

We investigated the agreement between the tuberculin skin test (TST) and the QuantiFERON-TB gold (QFT-G) assay in the diagnosis of latent tuberculosis infection (LTBI) in patients with systemic lupus erythematosus (SLE). Furthermore, we evaluated the factors associated with indeterminate results in the QFT-G assay in patients with SLE.

METHODS

We enrolled 136 patients with SLE prospectively, and compared them to 66 patients with rheumatoid arthritis (RA). In addition to the TST, QFT-G assay, patients' medications, and Bacillus Calmette-Guérin (BCG) vaccination status were also investigated. A positive TST or QFT-G assay result without an active tuberculosis lesion on chest x-ray was considered to indicate a diagnosis of LTBI.

RESULTS

The prevalence of LTBI was 26.5% in patients with SLE and 30.3% in patients with RA. The agreement between the TST and QFT-G assay was fair in SLE patients, but poor in RA patients. BCG vaccination was one factor associated with discordance between TST and QFT-G. Older age and higher SLE Disease Activity Index (SLEDAI) score were associated with a negative TST/positive QFT-G result in patients with SLE. Higher SLEDAI score and increased glucocorticoid dose were associated with an indeterminate result in the QFT-G assay for patients with SLE.

CONCLUSIONS

Agreement between the QFT-G assay and TST in patients with SLE was found to be fair. However, BCG vaccination status, age, and SLEDAI score are all factors that could result in discordance between the two tests. Indeterminate results from the QFT-G assay may be caused by a higher SLEDAI score or increased glucocorticoid dose.

Guidelines for the use of interferon-γ release assays in the diagnosis of tuberculosis infection

INTRODUCTION

Interferon-gamma release assays are widely used for the diagnosis of tuberculosis infection in low-prevalence countries. However, there is no consensus on their application. The objective of this study was to develop guidelines for the use of interferon-gamma release assays in specific clinical scenarios in Spain.

METHODS

A panel of experts comprising specialists in infectious diseases, respiratory diseases, microbiology, pediatrics and preventive medicine, together with a methodologist, formulated the clinical questions and outcomes of interest. They conducted a systematic literature search, summarized the evidence and rated its quality, and prepared the recommendations following the GRADE (Grading of Recommendations of Assessment Development and Evaluations) methodology.

RESULTS

The panel prepared recommendations on the use of interferon-gamma release assays for the diagnosis of tuberculosis infection in the contact-tracing study (both adults and children), health care workers, immunosuppressed patients (patients infected with human immunodeficiency virus, patients with chronic immunomediated inflammatory diseases due to start biological therapy and patients requiring organ transplant) and for the diagnosis of active tuberculosis. Most recommendations were weak, mainly due to the lack of good quality evidence to balance the clinical benefits and disadvantages of the interferon-gamma release assays as compared with the tuberculin skin test.

CONCLUSION

This document provides evidence-based guidance on the use of interferon-gamma release assays for the diagnosis of tuberculosis infection in patients at risk of tuberculosis or with suspicion of active disease. The guidelines will be applicable in specialist and primary care and in public health settings.

Screening of latent tuberculosis infection by interferon-γ release assays in rheumatic patients: a systemic review and meta-analysis

The aim of this study is to assess the diagnostic value of interferon-γ release assays (IGRAs) for latent tuberculosis infection (LTBI) in patients with rheumatic disease before receiving biologic agents. MEDLINE and EMBASE databases were used for searching studies concerning the evaluation on the performance of IGRAs [QuantiFERON-TB Gold (QFT-G), QuantiFERON-TB Gold In-Tube (QFT-GIT) and T-SPOT.TB] in rheumatic patients before biological therapy. After assessing the quality of all studies included in the review, we summarized the results in subgroups using forest plots and calculated pooled estimates if applicable. The search identified 11 studies with a total sample size of 1940 individuals. Compared with the tuberculin skin test (TST), the pooled agreements in QFT-G/GIT and T-SPOT.TB were 72 % (95 % confidence interval (CI) 65, 78 %) and 75 % (95 % CI 67, 83 %), respectively. BCG vaccination was positively correlated with positive rates of TST (pooled odds ratio (OR) 1.64, 95 % CI 1.06, 2.53). Compared with TST, IGRAs were better associated with the presentence of one or more tuberculosis (TB) risk factors. Neither steroid nor disease-modifying anti-rheumatic drugs (DMARDs) significantly affect positive IGRA results. In contrast, TST positivity was significantly impacted by the use of steroid (pooled OR 0.45, 95 % CI 0.30, 0.69), but less significantly by the use of DMARDs (pooled OR 0.78, 95 % CI 0.50, 1.21). In conclusion, in rheumatic patients with previous BCG vaccination or currently on steroid therapy, IGRAs would be the better choice to identify LTBI by decreasing the false-positivity and false-negativity rate compared with conventional TST.

The Significance of Sensitive Interferon Gamma Release Assays for Diagnosis of Latent Tuberculosis Infection in Patients Receiving Tumor Necrosis Factor-α Antagonist Therapy

OBJECTIVE

We compared two interferon gamma release assays (IGRAs), QuantiFERON-TB Gold In-Tube (QFT-GIT) and T-SPOT.TB, for diagnosis of latent tuberculosis infection (LTBI) in patients before and while receiving tumor necrosis factor (TNF)-α antagonist therapy. This study evaluated the significance of sensitive IGRAs for LTBI screening and monitoring.

METHODS

Before starting TNF-α antagonist therapy, 156 consecutive patients with rheumatic diseases were screened for LTBI using QFT-GIT and T-SPOT.TB tests. According to our study protocol, QFT-GIT-positive patients received LTBI treatment. Patients positive by any IGRAs were subjected to follow-up IGRA tests after completing LTBI-treatment and/or during TNF-α antagonist therapy.

RESULTS

At the initial LTBI screening, 45 (28.9%) and 70 (44.9%) patients were positive by QFT-GIT and T-SPOT.TB, respectively. The agreement rate between IGRA results was 78.8% (k = 0.56; 95% confidence interval [95% CI] = 0.43 to 0.68). Of 29 patients who were positive only by T-SPOT.TB in the initial screening, 83% (19/23) were persistently positive by T-SPOT.TB, while QFT-GIT testing showed that 36% (9/25) had conversion during TNF-α antagonist therapy. By the end of the follow-up period (218 to 1,264 days), four patients (4/137, 2.9%) developed active tuberculosis (TB) diseases during receiving TNF-α antagonist therapy. Among them, one was Q-T+, one was Q+T-, and the remaining two were Q-T- at the initial screening (Q, QuantiFERON-TB Gold In-Tube; T, T-SPOT.TB; +, positive; -, negative). Two (2/4, 50%) patients with TB reactivation had at least one prior risk factor consistent with previous TB infection.

CONCLUSION

This study demonstrated the need to capitalize on sensitive IGRAs to monitor for LTBI in at-risk patients for a more sensitive diagnosis in countries with an intermediate TB burden.

Diagnosis and Management of Latent Tuberculosis Infection

The post-2015 World Health Organization global tuberculosis strategy recognizes that elimination requires a focus on reducing the pool of latently infected individuals, an estimated 30% of the global population, from which future tuberculosis cases would be generated. Tackling latent tuberculosis infection requires the identification and treatment of asymptomatic individuals to reduce the risk of progression to active disease. Diagnosis of latent tuberculosis infection is based on the detection of an immune response to Mycobacterium tuberculosis antigens using either the tuberculin skin test or interferon-γ release assays. Current treatment requires the use of antibiotics for at least 3 months. In this article, we review the current knowledge of the natural history, immunology, and pathogenesis of latent tuberculosis, describe key population groups for screening and risk assessment, discuss clinical management in terms of diagnosis and preventative treatment, and identify areas for future research.

QuantiFERON-TB Gold In-Tube assay for screening arthritis patients for latent tuberculosis infection before starting anti-tumor necrosis factor treatment

Background

Patients undergoing anti-tumor necrosis factor (TNF) treatment are at an increased risk of reactivating a latent tuberculosis infection (LTBI). This study evaluated the effectiveness of the QuantiFERON-TB Gold In-Tube (QFT) assay for diagnosing LTBI in arthritis patients undergoing anti-TNF treatment.

Methods

We enrolled 342 consecutive patients from August 2007 to October 2013: 176 (51.5%) patients with ankylosing spondylitis and 166 (48.5%) with rheumatoid arthritis. Screening tests included tuberculin skin test (TST) and QFT assay. Positive QFT results, regardless of TST results, were considered an indicator for LTBI treatment.

Results

Bacillus Calmette-Guérin scars were found in 236 (69.0%) patients. Of 342 patients, TST and QFT were positive in 122 (35.7%) and 103 (30.1%) patients, respectively, and discordant in 101 (29.5%) patients. During a median follow-up duration of 41.7 months, five patients (1.5%) developed TB in a median of 20.8 months after initiation of anti-TNF treatment (428/100,000 person-years). TB did not occur in 62 TST+/QFT+ patients who received LTBI treatment. Of 41 TST−/QFT+ patients who received LTBI treatment, one (2.4%) developed TB 20.5 months after starting anti-TNF treatment (705/100,000 person-years). Of 60 TST+/QFT− patients who did not receive LTBI treatment, two (3.3%) developed TB 20.8 and 22.0 months after starting anti-TNF treatment (871/100,000 person-years). Of 179 TST−/QFT− patients, two (1.1%) developed TB 7.2 and 22.7 months, respectively, after initiating anti-TNF treatment (341/100,000 person-years). TB incidence rate during the follow-up period did not differ among TST−/QFT+, TST+/QFT−, and TST−/QFT− patients (P = 0.661).

Conclusion

QFT might be used instead of TST for diagnosing LTBI in patients before starting anti-TNF therapy in countries, such as Korea, where the TB prevalence is intermediate and the BCG vaccination is mandatory at birth. In the absence of a true gold standard test for LTBI, however, there is still a risk of TB development during anti-TNF treatment.

Assessment of tuberculosis infection during treatment with biologic agents in a BCG-vaccinated pediatric population

Biologic therapies, such as tumor necrosis factor-alpha (TNF-α) blockers, are commonly used to treat rheumatological diseases in childhood. Screening patients for tuberculosis (TB) is highly recommended before starting therapy with TNF-α blockers. Despite appropriate screening, TB still remains a problem in patients receiving anti-TNF therapy in countries where TB is not endemic. TB in anti-TNF-treated patients is often diagnosed late due to altered presentation, and this delay results in high morbidity and mortality with a high proportion of extrapulmonary and disseminated disease. The aim of this study is to show the course of TB disease in children who are on biologic therapy, in an era where many of the children are BCG-vaccinated and TB is intermediately endemic. We recruited 71 patients with several types of inflammatory diseases. Six of them had a positive test result during TB screening and began taking isoniazid (INH) prophylactically. During the 3 years of follow-up, none of these patients developed TB disease. Biologic agents can be safely used in a BCG-vaccinated pediatric population, as long as patients are closely monitored to ensure that any cases of TB will be detected early.

Follow-up testing of interferon-gamma release assays are useful in ankylosing spondylitis patients receiving anti-tumor necrosis factor alpha for latent tuberculosis infection

We evaluated the utility of follow-up interferon-gamma release assays (IGRAs) for the diagnosis of reactivation of latent tuberculosis infection (LTBI) or new tuberculosis in ankylosing spondylitis (AS) patients receiving anti-tumor necrosis factor alpha (anti-TNFα). The study participants (n=127) had a negative IGRA screening before receiving anti-TNFα and were evaluated by follow-up IGRA. We retrospectively examined data of the subjects according to age, gender, tuberculosis prophylaxis, concomitant medications, IGRA conversion and anti-TNFα, including type and treatment duration. The median duration of anti-TNFα was 21.5 months, and the median age was 35.3 yr. Of the 127 patients, IGRA conversion was found in 10 patients (7.9%). There was no significant variation between IGRA conversion rate and any risk factors except for age. IGRA conversion rate was not significantly different between AS and rheumatoid arthritis (P=0.12). IGRA conversion was observed in AS patients receiving anti-TNFα in Korea. A follow-up IGRA test can be helpful for identifying LTBI or new tuberculosis in AS patients receiving anti-TNFα.

Gamma interferon release assays for detection of Mycobacterium tuberculosis infection

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

Interferon-gamma release assays versus tuberculin skin testing in patients with rheumatoid arthritis

OBJECTIVE

The aim of this study was to analyze the results of interferon-gamma release assays (IGRAs) and tuberculin skin tests (TST) performed to detect latent tuberculosis infection (LTBI) in patients with rheumatoid arthritis (RA).

METHODS

Interferon-γ release assays and TST test results were summarized and systematically reviewed.

RESULTS

Four hundred and five RA patients and 339 controls that underwent IGRA and/or TST were identified in seven studies. Five studies were case-control studies and two were cross-sectional studies. Among RA patients, the IGRA positivity rate was 31.6% (89/282; range 11.4%-44.6%), and the TST positivity rate was 23.0% (78/339; range from 14.60% to 45%). Concordance rates ranged from 40% to 76% and discordance rates from 24% to 29.7%. Agreement between IGRAs and TST in RA was poor (69.6%, k = 0.33, 95% CI 0.188-0.478). The IGRA positivity rate was 31.0% in RA and 40.0% in controls, which was not significant (relative risk [RR] 0.802, 95% CI 0.629-1.023, P = 0.075). The TST positivity rate was 24.7% in RA and 50.5% in controls, and this difference was not significant (RR 0.680, 95% CI 0.331-1.339, P = 0.295).

CONCLUSIONS

Positivity rates of IGRA and TST were 31.6 and 23.0%, respectively, in RA patients. Agreement between IGRA and TST results in RA was poor. Our data suggest that both IGRA and TST are needed to detect LTBI in RA.

Risk of tuberculosis infection in anti-TNF-α biological therapy: from bench to bedside

Anti-tumor necrosis factor-α (TNF-α) biological agents, including soluble TNF-α receptors and anti-TNF-α monoclonal antibodies, bring new hope for treating rheumatic diseases such as rheumatoid arthritis, but also increase the risk of infection, especially tuberculosis (TB) infection. Recent findings have shown that the physiological TNF-mediated signaling was somehow impaired by TNF antagonists, leading to the exacerbation of chronic infection associated with aberrant granuloma formation and maintenance. Although both receptor and antibody agents appear to pose an equally high risk in causing development of new TB infections, monoclonal anti-TNF-α antibody seems more inclined to reactivate latent TB infection. This review is focused on the underlying mechanisms that cause the TB risk in the anti-TNF-α therapy and also the strategies to deal with it, with the aim of reducing the TB incidence during anti-TNF-α biological therapies.

Interferon-Gamma Release Assays versus Tuberculin Skin Testing for the Diagnosis of Latent Tuberculosis Infection: An Overview of the Evidence

A profusion of articles have been published on the accuracy and uses of interferon-gamma releasing assays. Here we review the clinical applications, advantages, and limitations of the tuberculin skin test and interferon-gamma release assays and provide an overview of the most recent systematic reviews conducted for different indications for the use of these tests. We conclude that both tests are accurate to detect latent tuberculosis, although interferon-gamma release assays have higher specificity than tuberculin skin testing in BCG-vaccinated populations, particularly if BCG is received after infancy. However, both tests perform poorly to predict risk for progression to active tuberculosis. Interferon-gamma release assays have significant limitations in serial testing because of spontaneous variability and lack of a validated definition of conversion and reversion, making it difficult for clinicians to interpret changes in category (conversions and reversions). So far, the most important clinical evidence, that is, that isoniazid preventive therapy reduces the risk for progression to disease, has been produced only in tuberculin skin test-positive individuals.

Interferon-γ release assays versus tuberculin skin test for targeting people for tuberculosis preventive treatment: an evidence-based review

OBJECTIVES

To assess whether Interferon-γ release assays (IGRAs) reduce the number of people considered for tuberculosis (TB) preventive treatment without increasing subsequent active disease.

METHODS

Longitudinal studies with both tuberculin skin test (TST) and IGRAs were identified through a PubMed search. Reductions in diagnosis of TB infection and increases in incident TB in people considered not infected, using IGRAs either instead of TST or as a confirmatory test (two-step approach), were assessed.

RESULTS

In comparison with TST alone, the pooled reductions in diagnosis of TB infection obtained with IGRAs were 16.7% and 5.8% at 5 and 10 mm cut-offs respectively, and 24.5% and 12.4% at 5 and 10 mm respectively with the two-step approach. Compared with TST alone, incident TB among people considered not infected increased with the two-step approach (0.94% with T-SPOT(®).TB and 1.1% with QuantiFERON(®)-TB Gold In-Tube) in one of seven studies in high-income countries. In middle- and low-income countries, two of four studies presented increases (0.08 and 0.03 per 100 patient-years respectively) with the two-step approach.

CONCLUSIONS

In high-income countries, the use of IGRAs, either instead of TST or as confirmatory test reduces the number of people considered for preventive treatment, without a significant risk of subsequent active disease.