Clinical evaluation of QuantiFERON TB-2G test for immunocompromised patients

Indeterminate results of interferon gamma release assays in the screening of latent tuberculosis infection: a systematic review and meta-analysis

Objectives

We aimed to evaluate the indeterminate rate of interferon gamma release assays (IGRAs) in the detection of latent tuberculosis infection (LTBI).

Methods

On 15 November 2022, we searched the PubMed® (National Library of Medicine, Bethesda, MD, USA), Embase® (Elsevier, Amsterdam, the Netherlands), and Cochrane Library databases in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Two investigators independently extracted the study data and assessed their quality using a modified quality assessment of diagnostic accuracy studies (i.e., QUADAS-2) tool. A random-effects model was used to calculate pooled results.

Results

We included 403 studies involving 486,886 individuals and found that the pooled indeterminate rate was 3.9% (95% CI 3.5%-4.2%). The pooled indeterminate rate for QuantiFERON®-TB (QFT) was similar to that for T-SPOT®.TB (T-SPOT) [odds ratio (OR) = 0.88, 95% CI 0.59-1.32]; however, the indeterminate rate for a new generation of QFT (QFT-plus) was lower than that of T-SPOT (OR = 0.24, 95% CI 0.16-0.35). The indeterminate rate in the immunocompromised population was significantly higher than that in healthy controls (OR = 3.51, 95% CI 2.11-5.82), and it increased with the reduction of CD4+ cell count in HIV-positive patients. Children's pooled indeterminate rates (OR = 2.56, 95% CI 1.79-3.57) were significantly higher than those of adults, and the rates increased as the children's age decreased.

Conclusion

On average, 1 in 26 tests yields indeterminate IGRA results in LTBI screening. The use of advanced versions of the QuantiFERON-TB assay (QFT-plus), may potentially reduce the occurrence of an indeterminate result. Our study emphasizes the high risk of immunosuppression and young age in relation to indeterminate IGRA, which should receive more attention in the management of LTBI.

Systematic review registration

PROSPERO https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020211363, CRD42020211363.

The association between diabetes status and latent-TB IGRA levels from a cross-sectional study in eastern China

Background

There is a debate regarding the sensitivity of the QuantiFERON-TB Gold In-Tube (QFT) among people with diabetes, and prior studies have shown heterogeneous results. We evaluated whether the QFT TB antigen was modified among persons with differing diabetes status and other related risk factors.

Methods

A cross-sectional study of 5,302 people was conducted to screen latent tuberculosis infection (LTBI) in eastern China. The QFT assay was performed as an indicator of LTBI. Fasting plasma glucose (FPG) was collected from each participant; the definition of diabetes followed the guidelines from the American Diabetes Association. Participants were classified into normoglycemia, prediabetes, undiagnosed diabetes, and previously diagnosed diabetes to evaluate the relationship between the QFT TB antigen and distinct diabetes status.

Results

TB antigen values from the QFT were statistically different among participants with differing diabetes status (P = 0.008). Persons with undiagnosed diabetes had a higher TB antigen value (0.96 ± 0.20) than persons with normoglycemia (0.50 ± 0.02, P < 0.05). However, the TB antigen values demonstrated no significant difference among the four different diabetic groups when stratified by the standard cutoff for the QFT (P = 0.492 for the positive group and P = 0.368 for the negative group). In a linear regression model, we found that FPG, age, and smoking were positively associated with the QFT TB antigen value (P = 0.017, P < 0.001, and P < 0.001).

Conclusions

Diabetes status had little influence on the level of QFT TB antigen response among IGRA-positive persons. However, FPG, old age, and smoking were important risk factors for increasing levels of QFT TB antigen.

Repeatability of QuantiFERON-TB gold plus testing utilizing microparticle chemiluminescence

BACKGROUND

Detection of latent Mycobacterium tuberculosis (LTBI) in patients is important to prevent active infection and the spread of disease, particularly in vulnerable patient populations. In 2020, a kit on the high throughput Liaison XL (DiaSorin) became commercially available for the analysis of QuantiFERON-TB Gold Plus assay (Qiagen). Pilot testing indicated suboptimal repeatability of some samples with this assay. This study provides an extensive assessment of repeatability with DiaSorin system.

RESULTS

Repeat testing of 481 IGRA positive samples, demonstrated substantial variability upon repeat analysis. Repeat results for TB1 and TB2 tubes, showed 73.73% and 72.82% concordance with initial results, respectively. TB1 and TB2 tube values minus the nil (IU/mL) were significantly higher in samples that were repeat positive (p < 0.001). Repeat results had better concordance with initial results if both TB1 and TB2 tubes were positive. Samples with TB1 tube values minus the nil (IU/mL) ≥ 4.54 and TB2 tube values minus the nil (IU/mL) ≥ 4.78 were found to always repeat positive. Assigning a threshold of 1.55 IU/mL for the TB1 tube value minus the nil and 1.45 IU/mL for the TB2 tube value minus the nil yielded a positive predictive value ≥95%.

CONCLUSION

These results identified a potential role for retesting of select IGRA positive samples on the Diasorin Liaison XL platform due to the high proportion of samples that show a lack of repeatability. Additionally, we identified a threshold that would determine samples most likely to repeat test positive and which samples should be retested.

Interferon-Inducible Protein-10 as a Marker to Detect Latent Tuberculosis Infection in Patients with Inflammatory Rheumatic Diseases

It is important to identify cases of latent tuberculosis infection (LTBI) who are at risk for tuberculosis (TB) reactivation. We aimed to evaluate the performance of interferon (IFN)-gamma-inducible protein 10 (IP-10) as a marker to detect LTBI in patients with inflammatory rheumatic diseases (IRD). This study comprised 76 consecutive subjects with IRD. Patients with a history of TB or having active TB were excluded. In all patients, IP-10 level was measured and tuberculin skin test (TST) and QuantiFERON-TB Gold In-Tube test (QFT-GIT) were performed. Seventy patients with complete test results were analyzed. Twenty-one (30%) QFT-GIT-positive patients were defined as having LTBI. IP-10 yielded 2197 pg/mL cut-off point. At this cut-off point, IP-10 showed 89% specificity with a sensitivity of 91% (AUC: 0.950, 95% CI 0.906–0.994). TST, QFT-GIT, and IP-10 were positive in 77.1%, 30%, and 44.3% of the patients, respectively. Concordance among the results of TST, QFT-GIT, and IP-10 tests was evaluated. Agreement was poor between IP-10 and TST (58.6%, κ = 0.19), whereas it was good between QFT-GIT and IP-10 (84.3%, κ = 0.65). The results of the present study demonstrated that sensitivity and specificity of released IP-10 were as high as those of QFT-GIT in indicating LTBI in IRD patient group.

Past and Present Approaches to Diagnosis of Active Pulmonary Tuberculosis

Tuberculosis disease continues to contribute to the mortality burden globally. Due to the several shortcomings of the available diagnostic methods, tuberculosis disease continues to spread. The difficulty to obtain sputum among the very ill patients and the children also affects the quick diagnosis of tuberculosis disease. These challenges warrant investigating different sample types that can provide results in a short time. Highlighted in this review are the approved pulmonary tuberculosis diagnostic methods and ongoing research to improve its diagnosis. We used the PRISMA guidelines for systematic reviews to search for studies that met the selection criteria for this review. In this review we found out that enormous biosignature research is ongoing to identify host biomarkers that can be used as predictors of active PTB disease. On top of this, more research was also being done to improve already existing diagnostic tests. Host markers required more optimization for use in different settings given their varying sensitivity and specificity in PTB endemic and non-endemic settings.

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 after liver transplantation in a large center in New York City: QuantiFERON® -TB Gold-based pre-transplant screening performance and active tuberculosis post-transplant

INTRODUCTION

Pre-transplant screening for latent tuberculosis infection (LTBI) is a complex consideration that varies by institution. Inconsistent performance of interferon-gamma release assay (IGRA) further complicates screening. Data regarding LTBI screening outcomes and test characteristics in a large, foreign-born pre-transplant population within the United States are limited.

METHODS

In this retrospective study, patients who received QuantiFERON^® -TB Gold (QFT) prior to liver transplantation (LT) were included. Characteristics of patients were compared by QFT result, and predictors of indeterminate results were evaluated. Similar comparisons were performed between patients who developed active TB and those who did not.

RESULTS

Of 148 patients screened, the rate of positive, indeterminate, and negative testing was 13.5% (20/148), 27% (40/148), and 59% (88/148), respectively. An indeterminate QFT result was more than 16 times more likely in patients with a Model for End-stage Liver Disease score >25 (odds ratio [OR] 16.7; 95% confidence interval [CI], 2.1-132.0; P = .008) and more than 4 times when performed in our institution's lab compared with commercial lab (OR 4.1; 95% CI, 1.34-12.44; P = .013). The overall TB incidence was 1102/100 000 transplant cases. No patient who developed active TB had a positive QFT. All were born outside of the United States (P = .06) and had pre-transplantation chest imaging demonstrating granulomatous disease (P = .006).

CONCLUSION

Our experience further highlights the challenges of LTBI screening prior to LT and suggests that QFT may be a poor predictor of active TB in higher risk pre-transplant populations. Candidates should be screened as early as possible to optimize QFT performance, and local epidemiological data should be used to create institution-specific screening protocols in areas with large populations from TB-endemic regions. Management should consider TB risk factors, QFT, and imaging instead of reliance on QFT testing alone.

Performance of QuantiFERON®-TB Gold In-Tube assay in children receiving disease modifying anti-rheumatic drugs

BACKGROUND

To evaluate the performance of the Quantiferon^®-TB Gold In-Tube (QFT-IT) interferon (IFN)-γ assay for the detection of latent tuberculosis infection (LTBI) in children receiving anti-rheumatic treatment in a tertiary referral hospital of Northern Greece.

METHODS

A total of 79 consecutive children receiving anti-rheumatic treatment [of which 18 screened prior to antitumor necrosis factor (TNF)-α treatment] were tested using Mantoux tuberculin skin test (TST) and QFT-IT. Association of both tests with risk factors for latent tuberculosis and Bacillus Calmette-Guerin immunization was determined. Influence of age, TNF-α inhibitors, systemic corticosteroids, conventional disease modifying anti-rheumatic drugs (DMARDs) and total duration of therapy on the QFT-IT mitogen-induced response was evaluated.

RESULTS

Agreement between TST and QFT-IT results was moderate (k=0.38). Frequency of QFT-IT indeterminate results was low (2.5%). In patients with risk factors for LTBI, the odds of a positive IFN-γ assay was increased by a factor of 27.6 (P=0.002), whereas there was no positive TST. There was a significant difference in the mitogen-induced IFN-γ secretion among various treatments (P=0.038). TNF-α inhibitors were associated with increased mitogen-induced IFN-γ secretion compared to monotherapy with conventional DMARDs (P=0.008). All children screened prior to anti-TNF-α treatment exhibited a negative QFT-IT and no active TB disease was detected during a 2-year follow-up.

CONCLUSIONS

QFT-IT may be a more reliable test than TST for detection of LTBI in children with rheumatic diseases receiving anti-rheumatic treatment. Drug regimen might influence the mitogen-induced IFN-γ secretion and the effect of TNF-α inhibitors might vary according to the specific agent administered.

Diabetes Mellitus and Latent Tuberculosis Infection: A Systematic Review and Metaanalysis

Background

Despite the well-documented association between diabetes and active tuberculosis, evidence of the association between diabetes and latent tuberculosis infection (LTBI) remains limited and inconsistent.

Methods

We included observational studies that applied either the tuberculin skin test or the interferon gamma release assay for diagnosis of LTBI and that provided adjusted effect estimate for the association between diabetes and LTBI. We searched PubMed and EMBASE through 31 January 2016. The risk of bias of included studies was assessed using a quality assessment tool modified from the Newcastle-Ottawa scale.

Results

Thirteen studies (1 cohort study and 12 cross-sectional studies) were included, involving 38263 participants. The cohort study revealed an increased but nonsignificant risk of LTBI among diabetics (risk ratio, 4.40; 95% confidence interval [CI], 0.50-38.55). For the cross-sectional studies, the pooled odds ratio from the random-effects model was 1.18 (95% CI, 1.06-1.30), with a small statistical heterogeneity across studies (I2, 3.5%). The risk of bias assessment revealed several methodological issues, but the overall direction of biases would reduce the positive causal association between diabetes and LTBI.

Conclusions

Diabetes was associated with a small but statistically significant risk for LTBI. Findings from this review could be used to inform future cost-effectiveness analysis on the impact of LTBI screening programs among diabetics.

Interferon-Gamma Release Assays for the Diagnosis of Tuberculosis: A Systematic Review and Meta-analysis

BACKGROUND AND OBJECTIVE

We conducted a systematic review and meta-analysis to compare the accuracy of the interferon-gamma release assays (IGRAs) and the tuberculin skin test (TST) for the diagnosis of Mycobacterium tuberculosis infection.

METHODS

We systematically searched PubMed, Embase, Cochrane library, and Web of Science databases for relevant published studies in recent decades and calculated pooled estimated sensitivities, specificities, DOR, and SROC curve of the QFT-IT, T-SPOT and TST. Random-effects models were used to assess estimates from studies with significant heterogeneity. Moreover, area under the curve was used to evaluate the accuracy of the tests.

RESULTS

Overall, 9 studies for QFT-IT, 12 studies for T-SPOT, and 16 studies for TST involving 3586 participants were included in this analysis. We found that sensitivities of the QFT-IT, T-SPOT, and TST were respectively 0.842 (95 % CI 0.811-0.870), 0.840 (95 % CI 0.814-0.864), and 0.665 (CI 0.635-0.693); specificities were respectively 0.745 (95 % CI 0.715-0.775), 0.658 (95 % CI 0.621-0.693), and 0.633 (CI 0.605-0.661); positive likelihood ratios were respectively 3.652 (95 % CI 2.180-6.117), 2.196 (95 % CI 1.727-2.794), and 1.825 (95 % CI 1.351-2.464); negative likelihood ratios were respectively 0.212 (95 % CI 0.109-0.414), 0.246 (95 % CI 0.161-0.377), and 0.556 (95 % CI 0.385-0.804); the SROC curves were 19.205, 10.397, and 3.810.

CONCLUSIONS

The two IGRAs showed better performance than TST for the diagnosis of the tuberculosis. However, neither of them showed stability in the diagnosis of TB.

The pros and cons of the QuantiFERON test for the diagnosis of tuberculosis, prediction of disease progression, and treatment monitoring

OBJECTIVE/BACKGROUND

Tuberculosis (TB) is a re-emerging disease with the advent of human immunodeficiency virus/AIDS infections. Discovered in 1959, diagnosed by various approaches and treated with antibiotics, the treatment of TB infection still poses public health concerns. Many cases of resistance and cross-resistance are observed. Diagnosis by culture, which is considered as the standard method, takes too long (20-30days) and is not suitable for extrapulmonary TB. QuantiFERON test, which is an indirect immunoassay based on blood, was developed. Much hope was placed in this new approach because it is based on blood, and many research teams have used it. We discuss the results of these different research groups who have used QuantiFERON for diagnosis, prediction of disease progression, or monitoring patients during the treatment of TB.

METHODS

Articles published in PubMed and documents published on Google were searched with the keywords: diagnosis and TB and QuantiFERON; TB and QuantiFERON and therapeutic monitoring; interferon-γ release assay; disease progression. These articles were read and analyzed.

RESULTS

The results were controversial with regards to using the QuantiFERON test for the diagnosis of TB according to the study population (ethnic group, bacillus Calmette-Guérin vaccine use) and according to the state of the immune system of the people studied (human immunodeficiency virus immunosuppression in cancer medication, hypertension). Also, research findings were controversial with regards to using QuantiFERON for monitoring TB patients on anti-TB medications. Also, the predictive positive value for the progression to TB among immigrant close contacts of both interferon-γ release assays was not better than that of the tuberculin skin test.

CONCLUSION

The QuantiFERON has advantages and limitations depending on the type of population studied. Recommendations are made to improve the sensitivity and specificity and to differentiate between latent and active TB by adding other specific proteins in the Mycobacterium tuberculosis antigen cocktail.

Extrapulmonary tuberculosis presented as fever of unknown origin in two patients with endstage kidney disease not on dialysis: usefulness of 18-FDG-PET/CT in the diagnostic localization of fever of unknown origin

Tuberculosis is one of the common causes of fever of unknown origin in patients with chronic kidney disease (CKD). Extrapulmonary tuberculosis is more common in CKD patients, and is, unfortunately, often underdiagnosed despite extensive assessments. Recently, fluorine-18-deoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) has been available in the diagnosis of malignancy, inflammatory and infectious diseases, and has become a useful diagnostic tool. Here, we present two cases of endstage kidney disease who presented with fever of unknown origin at the time of dialysis initiation. In both cases, although interferon-gamma-releasing assay was positive, combined conventional diagnostic modalities such as computed tomography and gallium-citrate scintigraphy failed to detect the sites infected with tuberculosis. By contrast, extrapulmonary lesions were detected by FDG-PET/CT and successfully treated with combined anti-tuberculous drugs. Diagnosis of extrapulmonary tuberculosis was confirmed by biopsy of the affected lymph node and lumbar spine, followed by PCR of the biopsied specimen. These cases highlight the importance of considering tuberculosis as one of the differential diagnoses in pre-dialysis CKD patients with persistent fever, and the usefulness of FDG-PET/CT in the detection of infectious sites of extrapulmonary tuberculosis.

Comparison of IGRA tests and TST in the diagnosis of latent tuberculosis infection and predicting tuberculosis in risk groups in Krakow, Poland

BACKGROUND

The objective of this study was to assess the prevalence of latent tuberculosis infection (LTBI) in risk groups in Krakow, using the QuantiFERON-TB Gold In-Tube (QFT-GIT) test and the tuberculin skin test (TST); we also sought to assess the rate of progression to active disease over 4-5 y of follow-up.

METHODS

QFT-GIT tests were performed on 785 subjects and the TST on 701 subjects from the risk groups of homeless persons, close contacts, periodic contacts, and residents of long-term care facilities (LTCFs), and subjects from a low risk group.

RESULTS

In homeless persons, close contacts, periodic contacts, LTCF residents, and low risk persons, a positive QFT-GIT was found in 36.7%, 27.2%, 27.0%, 21.1%, and 23.7% of subjects, respectively, while a positive TST was found in 55.8%, 47.4%, 47.6%, 43.2%, and 47.9%, respectively. Of 63 homeless subjects, 5 developed active TB over 248 person-y of follow-up (incidence rate (IR) 20 per 1000 person-y, 95% confidence interval (CI) 8.4-48.5); of 148 close contacts, 5 developed active TB over 740 person-y of follow-up (IR 7, 95% CI 2.8-16.2); of 145 periodic contacts, 2 developed active TB over 580 person-y of follow-up (IR 4, 95% CI 0.9-13.8). The IR per 1000 person-y (95% CI) among subjects with a positive QFT-GIT was 30 (9.0-86.1) for homeless subjects, 18 (5.7-54.7) for close contacts, and 13 (3.2-51.3) for periodic contacts. In Poland there is no policy for the provision of LTBI treatment to people with a positive QFT or TST; therefore, the estimated rates of disease progression were analysed amongst untreated subjects.

CONCLUSIONS

The prevalence of positive QFT-GIT and TST was high in the study risk groups. The best predictor of active TB in the homeless and close contacts groups was a positive QFT-GIT together with a positive TST.

Extremes of age are associated with indeterminate QuantiFERON-TB gold assay results

Results from 3,263 QuantiFERON-TB Gold in-tube (QFT-GIT) assays were analyzed to determine the impact of age on test performance. The proportion of indeterminate results was significantly higher in pediatric and elderly (9.1% and 7.4%, respectively) than in adult (2.6%; chi-square test, P < 0.0001) patients. A detailed analysis of indeterminate QFT-GIT assay results is presented.

Performance of QuantiFERON-TB Gold In-Tube test and Tuberculin Skin Test for diagnosis of latent tuberculosis infection in BCG vaccinated health care workers

Background

Tuberculin skin test (TST) has been used for years as an aid in diagnosing latent tuberculosis infection (LTBI) but it suffers from a number of well-documented performance and logistic problems. Quantiferon-TB Gold In Tube test (QFT-GIT) has been reported to have better sensitivity and specifity than TST. In this study, it was aimed to compare the performance of a commercial IFN-γ release assay (QFT-GIT) with TST in the diagnosis of HCWs at risk for latent TB infection in BCG vaccinated population.

Material/Methods

Hundred healthy volunteer health care workers were enrolled. All were subjected to TST and QFT-GIT. Results were compared among Health Care Workers (HCWs) groups in terms of profession, workplace, working duration.

Results

TST is affected by previous BCG vaccinations and number of cases with QFT-GIT positivity is increased in accordance with the TST induration diameter range. QFT-GIT result was negative in 17 of 32 TST positive (≥15 mm) cases and positive in 4 of 61 cases whose TST diameters are between 6–14 mm, that is attritutable to previous BCG vaccination(s). It was negative in all cases with TST diameters between 0–5 mm.

HCWs with positive QFT-GIT results were significantly older than the ones with negative results. Furthermore duration of work was significantly longer in QFT-GIT positive than in negative HCWs.

Conclusions

There was a moderate concordance between QFT-GIT and TST, when TST result was defined as positive with a ≥15 mm diameter of induration. We suggest that QFT-GIT can be used as an alternative to TST for detection of LTBI, especially in groups with high risk of LTBI and in population with routine BCG vaccination program.

Immune response to mycobacterial infection: lessons from flow cytometry

Detecting and treating active and latent tuberculosis are pivotal elements for effective infection control; yet, due to their significant inherent limitations, the diagnostic means for these two stages of tuberculosis (TB) to date remain suboptimal. This paper reviews the current diagnostic tools for mycobacterial infection and focuses on the application of flow cytometry as a promising method for rapid and reliable diagnosis of mycobacterial infection as well as discrimination between active and latent TB: it summarizes diagnostic biomarkers distinguishing the two states of infection and also features of the distinct immune response against Mycobacterium tuberculosis (Mtb) at certain stages of infection as revealed by flow cytometry to date.

Significant reduction in rate of indeterminate results of the QuantiFERON-TB Gold In-Tube test by shortening incubation delay

The QuantiFERON-TB Gold In-Tube (QFT-G IT) test (Cellestis Inc., Valencia, CA) is one of the gamma interferon release assays (IGRAs) that are promising tools for diagnosing active or latent Mycobacterium tuberculosis infections. We investigated the clinical and laboratory factors that affect the rate of indeterminate QFT-G IT test results. We also suggest a workflow strategy for achieving optimized test results using the QFT-G IT test for the diagnosis of active tuberculosis (TB) or latent TB infection. We performed statistical analysis using data from a retrospective review of medical records. The first phase included 683 QFT-G IT test results from 676 patients tested between January 2008 and May 2008, and the second phase included an additional 663 QFT-G IT test results from 653 patients tested between January 2008 and December 2008 at Samsung Medical Center, a tertiary care hospital in South Korea. Immunosuppressive drug therapy, underlying diseases, bedridden status, and hypoalbuminemia were significantly associated with indeterminate QFT-G IT test results. With reduction of the incubation delay during the test procedure from an average of 9.82 h to an average of 2.70 h with changes in the workflow, the frequency of indeterminate QFT-G IT test results was significantly reduced from 11.4% to 2.7%. With >6 h of incubation delay, however, the frequency of indeterminate QFT-G IT test results was increased in a statistically significant manner. This study demonstrates that not only clinicopathological factors but also laboratory factors, such as incubation delay, significantly affect the rate of indeterminate QFT-G IT test results; therefore, optimization of the test procedure may contribute to reductions in the rate of indeterminate QFT-G IT test results, which delay the diagnosis of TB.

Cost-effectiveness of QuantiFERON testing before initiation of biological therapy in inflammatory bowel disease

BACKGROUND

Anti-tumor necrosis factor α drugs are known to reactivate latent tuberculosis (TB). Current guidelines recommend screening for latent tuberculosis infection, with either tuberculin skin test (TST) or interferon gamma release assays such as QuantiFERON-TB Gold (QFT-G). Given the high rates of anergy to TST among immunosuppressed inflammatory bowel disease (IBD) patients, there is considerable interest in evaluating the superiority of interferon gamma release assays over TST in this patient population to diagnose latent tuberculosis infection. We compared the performance of TST and QFT-G for screening latent TB among immunosuppressed IBD patients based on prevalence, mortality risk from reactivation TB, and costs.

METHODS

A decision analytical model was constructed to compare 1-year outcomes and costs of using TST or interferon gamma release assay in an immunosuppressed IBD population.

RESULTS

Under the base case scenario, for every 1000 patients screened, the QFT-G strategy resulted in 0.53 deaths from reactivation TB compared with 1.92 deaths using TST. The QFT-G strategy results in 1.85 reactivation TB versus 6.7 reactivation TB using TST. The model was not sensitive to background prevalence of latent TB. The cost of QFT-G would have to be more than double for the TST strategy to become more cost effective. QFT-G also remains the cost-effective option unless the sensitivity of the TST improves by 400%.

CONCLUSIONS

Under a broad range of parameter values, the QFT-G strategy dominates the TST strategy in cost-effectiveness. Consideration should be given to QFT-G as the preferred method of identifying latent TB in all immunosuppressed IBD patients.

Indeterminate T-SPOT.TB Test Results in Patients with Suspected Extrapulmonary Tuberculosis in Routine Clinical Practice

Background

The two interferon-γ release assays such as QuantiFERON-TB Gold / In-Tube (QFT-TB) and T-SPOT.TB-are useful tools for the rapid diagnosis of tuberculosis (TB) but can yield indeterminate test results (ITRs). While some studies have identified risk factors for ITRs in the QFT-TB test, there have been few such studies for the T-SPOT.TB test. The aim of this study was to investigate the risk factors associated with ITRs in the T-SPOT.TB test.

Materials and Methods

From April 2008 to August 2010, all patients with suspected extrapulmonary tuberculosis (E-TB) were enrolled in a tertiary hospital in Korea. ITR was defined as < 20 spots in the positive control well or > 10 spots in the negative control well.

Results

Out of a total of 368 patients, 32 (8.7%, 95% CI, 6.0% to 11.7%) had ITRs in their T-SPOT.TB tests. The ITRs were due to a low mitogen response in 13 (40.6%) patients and to a high nil response in the other 19 (59.4%) patients. Statistical analysis revealed that old age, underlying diseases, immunosuppressive treatment, lymphopenia, and clinical manifestations of E-TB were not significantly associated with ITRs.

Conclusions

Indeterminate results in the T-SPOT.TB test are not affected by age, underlying disease, immunosuppressive treatment, lymphopenia, or clinical manifestations of E-TB, which are known risk factors for indeterminate results in the QFT-TB test.

Identification of latent tuberculosis infection in rheumatic patients under consideration for treatment with anti-TNF-α agents

INTRODUCTION

Immunosuppressive therapy with anti-tumour necrosis factor-α (TNF-α) agents in rheumatic patients modulates the immune system and may increase the risk of reactivating infections that are normally maintained in a latent state, such as tuberculosis. The purpose of this study was to analyse the value of QuantiFERON TB Gold In-Tube (QFT IT) and tuberculin skin test (TST) in BCG vaccinated patients with rheumatoid arthritis and ankylosing spondylitis who were qualified to receive TNF-α blockers.

MATERIAL AND METHODS

Ninety patients with rheumatoid arthritis and ankylosing spondylitis were included in the study. The control group consisted of 20 healthy participants. Chest X-ray, TST and QFT IT were carried out in all persons.

RESULTS

In rheumatic patients positive results of QFT IT and TST tests were identified in 15 cases (16.7%) whereas negative results of both tests were detected in 56 cases (62.2%). In the group of examined patients, 11 (12.2%) had QFT IT-/TST+ test results. In patients with QFT IT+/TST- status one active tuberculosis case was detected. In the control group QFT IT positive results were found in 4 cases (20%) and TST positive in 11 cases (55%). Treatment with TNF-α blockers was introduced in 26 rheumatology patients with the following test status: 3 with QFT IT+/TST+; 20 with QFT IT-/TST-; 3 with QFT IT-/TST+.

CONCLUSIONS

In the BCG vaccinated population the QFT IT assay may potentially improve the identification and selection for therapy for latent TB infection before treatment with anti-TNF agents.

Diagnostic value of ex vivo pleural fluid interferon-gamma versus adapted whole-blood quantiferon-TB gold in tube assays in tuberculous pleural effusion

BACKGROUND:

Noninvasive diagnosis of pleural tuberculosis (TB) remains a challenge due to the paucibacillary nature of the disease. As Mycobacterium tuberculosis (MTB)-specific T cells are recruited into pleural space in TB effusion; their indirect detection may provide useful clinical information.

OBJECTIVES:

Evaluation of pleural fluid interferon (INF)-γ levels vs Quantiferon–TB Gold In tube assay (QFT- IT) in blood and its adapted variants, using pleural fluid or isolated pleural fluid cells in the diagnosis of pleural TB.

METHODS:

Thirty-eight patients with pleural effusion of unknown etiology presented at Assiut University Hospital, Egypt, were recruited. Blood and pleural fluid were collected at presentation for INF-γ assays. Ex vivo pleural fluid INF-γ levels, QFT-IT in blood and its adapted variants were compared with final diagnosis as confirmed by other tools including blind and/or thoracoscopic pleural biopsy.

RESULTS:

The final clinical diagnosis was TB in 20 (53%), malignancy in 10 (26%), and effusion due to other causes in eight patients (21%). Ex vivo pleural fluid INF-γ levels accurately identified TB in all patients and were superior to the QFT-IT assays using blood or pleural fluid (70 and 78% sensitivity, with 60 and 83% specificity, respectively). QFT-IT assay applied to isolated pleural fluid cells had 100% sensitivity and 72% specificity. The optimal cut-off obtained with ROC analysis was 0.73 for TB Gold assay in blood assay, 0.82 IU/ml for the cultured pleural fluid assay, and 0.94 for isolated pleural cells assay.

CONCLUSION:

The ex vivo pleural fluid INF-γ level is an accurate marker for the diagnosis of pleural TB. QFT- IT assay in peripheral blood or its adapted versions of the assay using pleural fluid and/or washed pleural fluid cells had no diagnostic advantage over pleural fluid INF-γ in the diagnosis of pleural TB.

QuantiFERON-TB Gold In-Tube test for diagnosis of latent tuberculosis (TB) infection in solid organ transplant candidates: a single-center study in an area endemic for TB

BACKGROUND

The prevalence of Mycobacterium tuberculosis in transplant recipients is estimated to be 50 times higher than in the general population, with a mortality rate of around 40%. Diagnosis and treatment of latent tuberculosis (TB) infection (LTBI) is an essential strategy for TB control. In this study we compared the QuantiFERON-TB Gold In-Tube test (QFT) with the tuberculin skin test (TST) for detection of LTBI in solid organ transplant (SOT) candidates.

PATIENTS AND METHODS

Between March 2008 and September 2011, 187 transplant candidates, who were referred to the transplant clinic of Imam-Khomeini Hospital, were enrolled in the study. Patients were screened for LTBI with both QFT and TST. Twenty-three patients (12.3%) were excluded for failure to follow up. Concordance between the 2 tests, and variables associated with test discordance were assessed.

RESULTS

The mean age of patients was 40 years (range: 11-65) and male-to-female ratio was 1.2 (88/76). TST and QFT were positive in 26 (15.9%) and 33 (20.1%) patients, respectively. Five cases (3.1%) had indeterminate QFT. Overall agreement between QFT and TST was about 80% (k = 0.32, P-value = 0.0001).

CONCLUSION

Considering the fair overall agreement between the 2 tests, and greater ease of the QFT from the patient's point of view, QFT is recommended for detection of LTBI in SOT candidates.

Positive tuberculin skin test or interferon-gamma release assay in patients with radiographic lesion suggesting old healed tuberculosis

Radiographic lesions suggesting old healed tuberculosis (TB) is considered a risk factor for the subsequent development of active TB. The aim of this study was to estimate the positive rates of tuberculin skin test (TST) and interferon-gamma release assay (IGRA) in persons with old healed TB. Participants with lesions suggesting old healed TB on chest images and controls without such lesions were prospectively enrolled between January 1, 2010, and January 31, 2011. TST and the QuantiFERON-TB Gold In-Tube test (QFT-GIT) were performed. In total, 193 participants with old healed TB and 126 controls were recruited. The rates of positive TST and QFT-GIT among patients with old healed TB were 54.6% and 77.7%, respectively. The rates of positive TST and QFT-GIT among patients without old healed TB were 38.9% and 61.9%. Sixteen percent of participants with old healed TB showed negative results by both TST and QFT-GIT. The positive rate of TST waned among participants with old healed TB who were older than 60 yr, whereas QFT-GIT positivity was unaffected by age. The positive rates of TST and IGRA among participants with radiographic lesions suggesting old healed TB was higher than without those lesions. In addition, IGRA may be more accurate than TST for the detection of latent TB infection, especially in populations of individuals older than 60 yr.

Factors Associated with Indeterminate and False Negative Results of QuantiFERON-TB Gold In-Tube Test in Active Tuberculosis

BACKGROUND

The sensitivities and specificities of interferon-gamma release assays (IGRAs) vary among different population studies, and the data on the routine use of IGRAs are limited. The aim of this study was to evaluate the role of QuantiFERON-TB Gold In-Tube (QFT-GIT) test in the diagnosis of active tuberculosis.

METHODS

We conducted a prospective study, enrolling 77 patients with suspected pulmonary tuberculosis (TB), at a secondary care teaching hospital in Seoul.

RESULTS

In total, 12 (15.6%) patients showed indeterminate results due to positive control failure on the QFT-GIT test. Indeterminate results were significantly associated with the elderly, history of the intensive care unit stay, lymphocytopenia, especially low CD4 count, increased C-reactive protein and decreased protein levels. Of the 77 patients, 44 (57.1%) were diagnosed with active pulmonary tuberculosis, and the percentage of false negative results of the QFT-GIT was 36.4% (vs. 31.8% with TST). In the TB group with >65 years old (n=12), the proportions of the indeterminate (33.3% vs. 3.1%) and the false negative results (58.3% vs. 25.0%) of the QFT-GIT were significantly higher than in the younger TB group (n=32).

CONCLUSION

Indeterminate and false negative results of QFT-GIT test were not infrequent in tuberculosis, especially in the elderly. Care should be considered for the interpretation with the elderly, immunocompromised, chronic and severely diseased patients.

Comparison of QuantiFERON-TB Gold test and tuberculin skin test for the identification of latent Mycobacterium tuberculosis infection in lupus patients

The tuberculin skin test (TST) has low sensitivity for the diagnosis of tuberculosis (TB). QuantiFERON-TB Gold (QFT-G) is an IFN-gamma-release assay that measures the release of interferon-gamma after stimulation in vitro by Mycobacterium tuberculosis antigens using ELISA. The main advantage of this assay compared with TST is the lack of cross-reaction with Bacillus Calmette-Guérin (BCG) as well as most of non-tuberculous mycobacteria. The aim of our study is to compare QFT-G with TST for the detection of latent tuberculosis infection (LTBI) among patients with systemic lupus erythematosus (SLE).

Methods: Seventy-eight patients with SLE and 49 healthy subjects (HCs) participated in the study. All patients and controls were interviewed for a history of TB then BCG vaccinations were recorded and chest X-rays were examined for a sign of TB infection. QTF-G and TST were performed on both patients and controls. QTF-G results were recorded as positive, negative or indeterminate. A positive TST for SLE was defined as ≥5 mm.

Results: Seventy-six SLE patients (97.4%) had been BCG vaccinated. Similar to the HC (28.5%), 19 of 78 (24.3%) SLE patients had positive QTF-G. Two patients had an indeterminate result. The agreement between QTF-G and TST was 49/76 (64.4%) (κ = 0.33). There were fewer positive QFT-G test results than positive TST results (24.3% vs. 50%; p < 0.01). Twenty-two (28.9%) patients were TST(+)/QTF-G(−) while only 3(3.9%) patients were TST(−)/QTF-G(+). When the positive TST was defined as ≥10 mm indurations, which is the cut-off in screening for LTBI in Turkey, the agreement between two tests increased up to 58/76 (76.3%) with a κ value of 0.47. The mean TST measurements was higher in QTF-G positive patients (13.4 ± 8.8 mm) than the QTF-G negative patients (4 ± 5.3 mm) ( p < 0.001).

Discussion: In a TB-endemic and BCG vaccinated population, the QuantiFERON-TB Gold assay seemed to be a more accurate test for the detection of LTBI in SLE patients. Although 5 mm is usually accepted to be the standard cut-off for TST in immunocompromised patients such as SLE, the level of agreement between QTF-G and TST was better with a 10 mm cut-off in our population.

Questionable role of interferon-γ assays for smear-negative pulmonary TB in immunocompromised patients

OBJECTIVE

The purpose of this study was to examine the usefulness of the TST and the interferon-γ release assays (IGRA) for diagnosing smear-negative pulmonary TB in immunocompromised patients in an intermediate TB burden.

METHODS

We conducted a prospective study enrolling 119 immunocompromised participants with suspected smear-negative pulmonary TB in Seoul, South Korea. Clinical assessment, TST, QuantiFERON-TB Gold In Tube (QFT-GIT), and T-SPOT.TB were performed in immunosuppressed condition.

RESULTS

All participants were categorized according to the type of immunosuppression: 29 patients with diabetes mellitus, 53 with malignancy, 23 with taking immunosuppressive drugs, and 14 with end stage renal disease. IGRA sensitivity and specificity (95% CI) were: QFT-GIT [59.0% (44.9-72.0)] and [61.3% (54.4-67.6)] and T-SPOT.TB [72.0% (54.2-86.2)] and [42.3% (33.8-49.1)], respectively. For TST, sensitivity was 41.2% (28.3-50.8) and specificity was 91.8% (85.8-96.30). The sensitivities of the three diagnostic methods tended to be lower in the immunosuppressive drug group than in other groups (QFT-GIT 11.1%, T-SPOT.TB 40.0% and TST 25.0% in patients with taking immunosuppressive drugs). Among 111 patients who underwent a chest CT examination, there were no significant differences in the CT findings between the immunocompromised TB and non-TB patients.

CONCLUSIONS

The IGRAs and TST had no value as a single test either to rule-in or rule-out active TB in immunocompromised patients in an intermediate burden.

Prednisolone treatment affects the performance of the QuantiFERON gold in-tube test and the tuberculin skin test in patients with autoimmune disorders screened for latent tuberculosis infection

BACKGROUND

During screening for latent tuberculosis infection (LTBI), before anti-tumor-necrosis-factor-α treatment, most patients are already receiving immunosuppressive therapy. The objective was to evaluate the performance of the QuantiFERON Gold In-Tube (QFT-IT) and the Tuberculin Skin Test (TST).

METHODS

A prospective multicenter study included 248 patients with ulcerative colitis (39), Crohn's disease (54), rheumatoid arthritis (111), and spondylo-arthropathy (44).

RESULTS

QFT-IT was positive in 7/248 (3%), negative in 229 (92%), and indeterminate in 12 (5%). TST was positive in 54/238 (23%) patients. Chest x-ray was suspect for tuberculosis in 5/236 (2%), and 35/167 (21%) had ≥1 risk-factors for infection with Mycobacterium tuberculosis. The main finding was a pronounced negative effect on QFT-IT and TST performance associated with prednisolone treatment. During prednisolone treatment interferon gamma (IFN-γ) response to mitogen stimulation was impaired (median IFN-γ response 4.9 IU/mL; interquartile range [IQR] 0.8 to ≥10.0) compared to patients 1) not receiving corticosteroids (median ≥10.0; IQR 5.0 to ≥10.0; P = 0.0015) or 2) receiving long-acting corticosteroids (median >10.0; IQR 9.7 to >10.0; P = 0.0058). Prednisolone treatment was strongly associated with negative TST, adjusted odds ratio (AOR) 0.22 (0.1-0.8; P = 0.018), and with an increased risk of indeterminate QFT-IT results AOR 16.1 (4.1-63.2; P < 0.001), whereas no negative effect was found for long-acting corticosteroids. Doses of ≥10 mg prednisolone were associated with a 27% risk of indeterminate results. Single use of azathioprine, methotrexate, or 5-aminosalicylate (5-ASA) did not affect the test results.

CONCLUSIONS

Oral prednisolone severely suppressed QFT-IT and TST performance, whereas the long-acting corticosteroids methotrexate, azathioprine, and 5-ASA did not have a similar detrimental effect. Patients should be screened for LTBI with QFT-IT or TST prior to initiation of prednisolone therapy and negative QFT-IT or TST results interpreted with caution in patients treated with any corticosteroid until further data are available.

Predictors of indeterminate IFN-γ release assay in screening for latent TB in inflammatory bowel diseases

BACKGROUND

IFN-γ release assays (IGRA), widely used for latent tuberculosis screening prior to anti-TNF-α treatment, are limited by indeterminate results in patients under immunomodulatory (IM) therapy. The aim of our observational study was to delineate factors associated with indeterminate IGRA results.

METHODS

A total of 190 patients with inflammatory bowel disease were included. IGRA was indeterminate if the result of IFN-γ concentration was < 0·35 IU mL(-1) for tuberculosis-specific antigens and < 0·5 IU mL(-1) for the positive control. Predictors for indeterminate results were delineated from multivariate logistic regression.

RESULTS

IFN-γ release assays was indeterminate in 26/190 (13·7%) patients. Indeterminate IGRA were associated with lower serum albumin levels (odds ratio [OR] 0·88, 95% confidence interval [CI] 0·79-0·96), lower absolute lymphocyte count (OR 0·39, 95% CI 0·18-0·75) and double IM therapy (OR 2·98, 95% CI 0·95-8·90). Sub-analysis of IM therapy revealed an association of steroid therapy with indeterminate IGRA (OR 3·19, 95% CI 1·35-7·70). Hypoalbuminaemia increased the risk of indeterminate IGRA by (OR 2·97, 95% CI 1·03-8·61) and lymphopaenia by (OR 3·28, 95% CI 1·41-7·65). After a mean of 18·5 ± 14·4 days, retesting of IGRA in 18 patients with indeterminate results yielded 9 negative vs. 9 indeterminate results.

CONCLUSIONS

Our results reveal associations of indeterminate IGRA with low serum albumin levels and absolute lymphocyte count and double IM therapy. IGRA testing appears best to be performed prior to initiation of IM therapy in patients with inflammatory bowel disease.

The Challenging Evaluation of Patients with Severe Psoriasis for Latent Tuberculosis: An Important Indication for IGRA

It is well-established that tumour necrosis factor (TNF)-α-antagonist regimens are advisable for the control of moderate to severe psoriasis; however the application of these agents is associated with increased risk of TB reactivation. Screening for latent tuberculosis infection (LTBI) is indispensable prior to treatment inception in order to diminish the risk of active TB. Although tuberculin skin test (TST) still represents a useful tool for LTBI detection, it is difficult to be performed and read in patients with extensive psoriatic lesions. In this paper, we report the case of a 65-year-old male with severe psoriasis, who was evaluated by an interferon-gamma release assay (IGRA) for LTBI diagnosis prior to anti-TNF-α therapy. Furthermore, the physiological aspects of interferon-gamma release assays are discussed emphasizing the value of these novel immunodiagnostic tests (IGRAs) for presumable LTBI in all patients with extensive skin disorders.

The clinical utility of tuberculin skin test and interferon-γ release assay in the diagnosis of active tuberculosis among young adults: a prospective observational study

Background

The roles of the tuberculin skin test (TST) and QuantiFERON^®-TB Gold In-Tube assay (QFT-IT) in the diagnosis of active tuberculosis (TB) are not clear in young adults. We evaluated the diagnostic accuracy of the TST and QFT-IT in smear-negative TB among young adults with no underlying disease.

Methods

We prospectively enrolled 166 young participants 20-29 years of age with suspected active TB in a military hospital of South Korea. The TST and QFT-IT were performed for all participants.

Results

Of the 143 patients included in the analysis, active TB was diagnosed in 100 (69.9%). There were 141 male patients, none of whom had immunosuppressive disease. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of TST were 94% (95% CI, 87-98%), 88% (95% CI, 74-96%), 95% (95% CI, 88-98%), and 86% (95% CI, 72-94%), respectively. The sensitivity, specificity, PPV, and NPV of the QFT-IT were 93% (95% CI, 86-97%), 95% (95% CI, 81-99%), 98% (95% CI, 92-99%), and 84% (95% CI, 69-93%), respectively. No significant differences were found between the TST and QFT-IT in any statistic.

Conclusions

Both the TST and QFT-IT showed high sensitivity and specificity in differentiating active TB from other diseases. The diagnostic accuracy of these two tests did not differ significantly when applied to this clinical population of young, immunocompetent adults in whom neonatal BCG vaccination was common, there was no history of previous TB and in whom suspicion of TB was high.

Trial registration

ClinicalTrials.gov: NCT00982969

Detection and management of latent tuberculosis in liver transplant patients

The optimal means for detecting and managing liver transplantation (LT) patients with latent tuberculosis (TB) are not well defined. Our study aims were to (1) determine the frequency and risk factors of latent TB in a large cohort of consecutive adult LT candidates and (2) determine the safety and efficacy of isoniazid treatment in LT recipients with latent TB. A review of patients assessed for latent TB by skin testing using purified protein derivative (PPD; January 2004 to September 2008) or with the interferon-γ release assay QuantiFERON-TB Gold (QFT; March 2008 to October 2009) was undertaken. The baseline clinical features and outcomes of subjects with latent TB and subjects without latent TB were compared. Twenty-five of 420 subjects (6.0%) were positive for PPD. In comparison, 11 of 119 subjects (9.2%) had a positive QFT assay, and 15 others (13%) had indeterminate results. Both PPD-positive and QFT-positive subjects were less likely to be Caucasian than subjects without latent TB (p < 0.001). The 3-year survival rate of the 25 LT recipients with latent TB was similar to that of the 296 LT recipients without latent TB (78.7% versus 74.6%, P = 0.58). Fifteen of the 25 latent TB patients received isoniazid at a mean of 0.67 months after LT. Although isoniazid was discontinued in 8 subjects because of possible side effects, none of the 25 latent TB patients developed TB reactivation after transplantation with a mean follow-up of 33 months. In conclusion, both QFT testing and PPD testing demonstrate similar rates of detecting latent TB infection in American LT candidates, but QFT testing also leads to a moderate rate of indeterminate test results. Early isoniazid chemoprophylaxis after LT is poorly tolerated and is frequently discontinued.

QuantiFERON TB gold testing for tuberculosis screening in an inflammatory bowel disease cohort in the United States

BACKGROUND

Reactivation of latent Mycobacterium tuberculosis (TB) is a rare, yet devastating infectious complication associated with anti-tumor necrosis factor alpha (TNF-α) therapy. We evaluated the performance of the QuantiFERON TB Gold test (QFT-G) for TB screening in a cohort of inflammatory bowel disease (IBD) patients in the United States.

METHODS

We performed a retrospective, observational study of patients initiated and/or maintained on an anti-TNF-α agent in a single IBD referral center and recorded the frequency and the test results of QFT-G testing and the rate of TB reactivation.

RESULTS

512 QFT-G tests were done in 340 patients. Five patients (1.5%) had a positive, nine (2.7%) indeterminate, and 326 patients (95.8%) had a negative QFT-G. After a mean follow-up of 17 months there was one case of TB reactivation (0.3%). The use of immunosuppressive therapy or anti-TNF therapy at the time of testing did not affect the results of the QFT-G testing. Test-retest had substantial concordance (κ = 0.72). 25% of patients (n = 85) had TST testing. Concordance between the TST and QFT-G was found to be moderate (κ = 0.4152, P = 0.0041).

CONCLUSIONS

Most patients with negative QFT-G tolerated anti-TNF therapy with no evidence of TB reactivation. Concomitant use of immunosuppressive therapy or anti-TNF did not seem to affect QFT-G results. One patient had an indeterminate QFT-G while on infliximab and later developed miliary TB. Concordance with TST is moderate.