QuantiFERON TB-2G test for patients with active tuberculosis stratified by age groups

A regression predictive model for QuantiFERON-TB Gold Plus® indeterminate results in immunosuppressed patients

Background

Screening for latent tuberculosis infection using Interferon-Gamma Release Assays is a routine procedure prior to the initiation of anti-tumor necrosis factor (TNF) biotherapy or immunosuppressive therapy. However, indeterminate results are relatively frequent and are an obstacle to treatment initiation.

Aim

The aim of this cross-sectional study was to estimate the frequency of indeterminate QuantiFERON-TB Gold Plus® test results in Tunisian patients, and to analyze the potential clinico-biological risk factors associated with these indeterminate results.

Methods

Whole blood samples from 712 patients being monitored for autoimmune diseases and candidates for anti-TNF biotherapy or switch of immunosuppressive therapy were used to screen for latent tuberculosis infection using the QuantiFERON-TB Gold Plus® test. Based on literature background, the following variables were tested for the association with indeterminate results: gender, age, diabetes, immunosuppressive drugs, lymphocyte count, Neutrophil-to-lymphocyte ratio, serum albumin, and estimated glomerular filtration rate.

Results

The QuantiFERON-TB Gold Plus® test was negative in 572 (80.3%) patients, positive in 106 (14.9%), and indeterminate in 34 (4.8%) cases. Positive results were significantly associated with a family history of confirmed and treated tuberculosis, OR (95% CI) = 52 (20.2-134.3). The use of immunosuppressive drugs and duration of treatment were significantly associated with the occurrence of indeterminate results: OR (95% CI) = 24.5 (5.8-103) and OR (95% CI) = 1.004 (1.002-1.007), respectively. Biologically, lymphopenia, hypoalbuminemia, and decreased estimated glomerular filtration rate were significant risk factors for indeterminate results: p = 5 E-6, p = 4.3 E-4, and p = 0.002, respectively. Thus, a multiple logistic regression model based on these three biological parameters enabled us to develop a predictive score for indeterminate results with a sensitivity of 91.2% and a specificity of 99.9%, AUC = 0.9964 (0.9917-1), p = 2.8 E-52.

Conclusion

Immunosuppressive therapy, lymphopenia, hypoalbuminemia, and kidney failure appeared to be risk factors for indeterminate QuantiFERON-TB Gold Plus® results.

Utility of interferon-gamma releasing assay for the diagnosis of active tuberculosis in children: A systematic review and meta-analysis

INTRODUCTION

The accurate diagnosis of tuberculosis (TB) in children is essential for its effective management and control. Reliable diagnostic tools that are currently available for identifying TB infection include the in vivo tuberculosis skin test (TST) and ex vivo interferon-gamma release assays (IGRAs). This systematic review and meta-analysis aimed to evaluate the diagnostic accuracy of IGRAs in children.

METHODS

Of the 768 screened studies, 47 met the eligibility criteria. Data from 9065 patients, including 1086 (12.0 %) with confirmed TB, were included in the analysis. The overall quality of the included studies, assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 tool, was unclear.

RESULTS

The calculated pooled sensitivity and specificity of IGRAs in children were 0.85 (95 % confidence interval [CI]: 0.79-0.89) and 0.94 (95 % CI: 0.88-0.97), respectively. Subpopulation analysis revealed that the sensitivities and specificities were as follows: QuantiFERON tests: 0.83 (95 % CI: 0.74-0.89) and 0.93 (95 % CI: 0.87-0.96), T-SPOT: 0.87 (95 % CI: 0.79-0.91) and 0.99 (95 % CI: 0.85-1.00), IGRAs in children under 15 years: 0.77 (95 % CI: 0.43-0.94) and 0.96 (95 % CI: 0.84-0.97), and IGRAs in children under 5 years: 0.85 (95 % CI: 0.52-0.97) and 0.94 (95 % CI: 0.90-0.99), respectively.

CONCLUSIONS

This study demonstrated that the sensitivity and specificity of the IGRAs in children were moderate and high, respectively. Therefore, the IGRAs may be useful for detecting TB infection in children.

CLINICAL TRIAL REGISTRATION

The review protocol was prospectively registered with the University Hospital Medical Information Network Clinical Trials Registry (UMIN000046737).

Factors Influencing False-Negative Results of QuantiFERON-TB Gold In-Tube (QFT-GIT) in Active Tuberculosis and the Desirability of Resetting Cutoffs for Different Populations: A Retrospective Study

Objectives The value of QuantiFERON-TB Gold In-Tube (QFT-GIT) in the diagnosis of TB varies by population, comorbidities, and other factors. In this study, we aimed to investigate factors that influence false-negative results of QFT-GIT test in the diagnosis of TB as well as the impact of different cutoffs on the diagnostic value. Methods A total of 3562 patients who underwent QFT-GIT tests at Shanghai Pulmonary Hospital were enrolled retrospectively between May 2016 and May 2017. False-negative and false-positive results were analyzed using different clinical stratifications. The optimal cutoff values were established under different clinical conditions. Results Positive QFT-GIT results greatly shortened the time taken to diagnose smear-negative TB. The factors of age, smear and culture results, site of TB, comorbidity with tumors, white blood cell count, neutrophil count, and CD4/CD8 ratio were significantly correlated with false-negative QFT-GIT results (p < 0.05). Personalized cutoff values were established according to different influencing factors. The results showed high consistency between the smear-negative and total populations. Conclusion QFT-GIT can facilitate the early diagnosis of smear-negative TB. The diagnostic performance of the QFT-GIT test in the diagnosis of active TB was shown to be affected by many clinical factors. Personalized cutoff values may have superior value in the identification of active tuberculosis under different conditions.

Tuberculosis in the Elderly

The tuberculosis (TB) epidemic is most prevalent in the elderly, and there is a progressive increase in the notification rate with age. Most cases of TB in the elderly are linked to the reactivation of lesions that have remained dormant. The awakening of these lesions is attributable to changes in the immune system related to senescence. The mortality rate from tuberculosis remains higher in elderly patients. Symptoms of active TB are nonspecific and less pronounced in the elderly. Diagnostic difficulties in the elderly are common in many diseases but it is important to use all possible techniques to make a microbiological diagnosis. Recognising frailty to prevent loss of independence is a major challenge in dealing with the therapeutic aspects of elderly patients. Several studies report contrasting data about poorer tolerance of TB drugs in this population. Adherence to antituberculosis treatment is a fundamental issue for the outcome of treatment. Decreased completeness of treatment was shown in older people as well as a higher risk of treatment failure.

Screening for TB in Hospitalised Patients with Inflammatory Bowel Disease before Anti-TNF Therapy: Is QuantiFERON® Gold Testing Useful?

Background—Tumour necrosis factor alpha (TNFα) plays an important role in the pathogenesis of inflammatory bowel disease (IBD) and in immunity to Mycobacterium tuberculosis. Patients should be tested for latent tuberculosis infection using interferon-gamma release assays (IGRA/QF) prior to anti-TNFα therapy. Indeterminate QF results can delay anti-TNFα therapy. We sought to investigate factors associated with indeterminate QF results. Method—Retrospective study of all IGRA tests requested for gastroenterology patients in 2017. We compared inpatients and outpatients and investigated factors potentially associated with QF usefulness (steroid exposure, C-reactive protein (CRP), hypoalbuminaemia, thrombophilia). Results—We included 286 outpatients and 74 inpatients with IBD. Significantly more inpatients had an indeterminate IGRA (52.7% vs. 3.14% in outpatients; p < 0.0001). Laboratory parameters reflecting inflammation (high CRP, low albumin, low haemoglobin and high platelets) were also associated with an indeterminate QF (p < 0.0001). Exposure to steroids was more common in patients with an indeterminate QF (p < 0.0001). A binary logistic regression analysis revealed inpatient status and steroid exposure to be independently predictive of an indeterminate QF (p < 0.0001). Conclusion—There is a high chance of indeterminate QF results in inpatients. QF testing should ideally be performed in the outpatient setting at diagnosis.

Risk Factors for Indeterminate Interferon-Gamma Release Assay for the Diagnosis of Tuberculosis in Children-A Systematic Review and Meta-Analysis

Background: Interferon-gamma release assays (IGRA) are well-established immunodiagnostic tests for tuberculosis (TB) in adults. In children these tests are associated with higher rates of false-negative and indeterminate results. Age is presumed to be one factor influencing cytokine release and therefore test performance. The aim of this study was to systematically review factors associated with indeterminate IGRA results in pediatric patients. Methods: Systematic literature review guided by the preferred reporting items for systematic reviews and meta-analyses (PRISMA) searching PubMed, EMBASE, and Web of Science. Studies reporting results of at least one commercially available IGRA (QuantiFERON-TB, T-SPOT.TB) in pediatric patient groups were included. Random effects meta-analysis was used to assess proportions of indeterminate IGRA results. Heterogeneity was assessed using the I² value. Risk differences were calculated for studies comparing QuantiFERON-TB and T-SPOT.TB in the same study. Meta-regression was used to further explore the influence of study level variables on heterogeneity. Results: Of 1,293 articles screened, 133 studies were included in the final analysis. These assessed QuantiFERON-TB only in 77.4% (103/133), QuantiFERON-TB and T-SPOT.TB in 15.8% (21/133), and T-SPOT.TB only in 6.8% (9/133) resulting in 155 datasets including 107,418 participants. Overall 4% of IGRA results were indeterminate, and T-SPOT.TB (0.03, 95% CI 0.02-0.05) and QuantiFERON-TB assays (0.05, 95% CI 0.04-0.06) showed similar proportions of indeterminate results; pooled risk difference was-0.01 (95% CI -0.03 to 0.00). Significant differences with lower proportions of indeterminate assays with T-SPOT.TB compared to QuantiFERON-TB were only seen in subgroup analyses of studies performed in Africa and in non-HIV-infected immunocompromised patients. Meta-regression confirmed lower proportions of indeterminate results for T-SPOT.TB compared to QuantiFERON-TB only among studies that reported results from non-HIV-infected immunocompromised patients (p < 0.001). Conclusion: On average indeterminate IGRA results occur in 1 in 25 tests performed. Overall, there was no difference in the proportion of indeterminate results between both commercial assays. However, our findings suggest that in patients in Africa and/or patients with immunocompromising conditions other than HIV infection the T-SPOT.TB assay appears to produce fewer indeterminate results.

Evaluation of risk factors for false-negative results with an antigen-specific peripheral blood-based quantitative T cell assay (T-SPOT®. TB) in the diagnosis of active tuberculosis: A large-scale retrospective study in China

Objective To investigate the diagnostic efficacy of an interferon-γ release assay, T-SPOT^®. TB, for diagnosing active tuberculosis (TB) and to identify risk factors for false-negative results. Methods This retrospective study enrolled consecutive patients with active TB and with non-TB respiratory diseases to evaluate the risk factors for false-negative results when using the T-SPOT^®. TB assay for the diagnosis of active TB. Patients with active TB were categorized as having confirmed pulmonary TB, clinically diagnosed pulmonary TB or extrapulmonary TB (EPTB). Results This study analysed 4964 consecutive patients; 2425 with active TB and 2539 with non-TB respiratory diseases. Multivariate logistic regression analyses identified the following five factors that were all associated with an increased false-negative rate with the T-SPOT^®. TB assay: increased age (odds ratio [OR] 1.018; 95% confidence interval [CI] 1.013, 1.024); decreased CD8+ count (OR 0.307; 95% CI 0.117, 0.803); negative sputum acid-fast bacilli (AFB) smear staining (OR 1.821; 95% CI 1.338, 2.477); negative mycobacterial cultures (OR 1.379; 95% CI 1.043, 1.824); and absence of EPTB (OR 1.291; 95% CI 1.026, 1.623). Conclusions Increased age, decreased CD8+ count, negative sputum AFB smear results, negative sputum mycobacterial cultures and absence of EPTB might lead to an increased false-negative rate when using the T-SPOT^®. TB assay.

Diagnostic Significance of Mycobacterium tuberculosis T-cell Assays for Active Tuberculosis

BACKGROUND

Active tuberculosis (TB) with negative results of sputum smear is difficult to be identified. Till now, there is no effective and noninvasive diagnostic method. This study evaluated the diagnostic power of Mycobacterium tuberculosis T-cell (T.SPOT®.TB) assays for active TB.

METHODS

We retrospectively screened 450 suspected TB patients that were hospitalized in the Respiratory Department of Henan Province People's Hospital from June 2015 to June 2016. The patients were divided into the active, previous, and non-TB groups according to their final diagnosis. We evaluated the diagnostic value of the T-SPOT®.TB assay by constructing receiver operating characteristic (ROC) curves and calculating the optimal diagnostic cutoff value. In addition, we compared the levels of A antigen (ESAT-6) and B antigen (CFP-10) in active TB.

RESULTS

The sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, and negative likelihood ratio of T-SPOT®.TB for active TB were 89.78%, 63.16%, 0.56, 0.92, 2.47, and 0.16, respectively. For active TB, the area under the ROC curve (AUC) of the A antigen (0.89) was higher than that of the B antigen (0.86). The AUC of the A antigen for active TB was largest at a cutoff value of 13.5 spot-forming cells (SFCs) per 2.5 × 105 peripheral blood mononuclear cells (PBMCs). The AUC of the A and B antigens was 0.60 and 0.58 for previous TB. The levels of A and B antigen in the active TB group were significantly different from those in the previous- and non-TB groups (A antigen: χ2 = 105.41, P< 0.01 and B antigen: χ2 = 91.03, P< 0.01; A antigen: χ2 = 12.99, P< 0.01 and B antigen: χ2 = 8.56, P< 0.01, respectively). There were no significant differences in the levels of A and B antigens between the non-TB group and previous TB group (A antigen: χ2 = 1.07, P> 0.05 and B antigen: χ2 = 0.77, P> 0.05).

CONCLUSIONS

T-SPOT®.TB has high sensitivity and specificity for the diagnosis of active TB at a cutoff value of 13.5 SFCs per 2.5 × 105 PBMCs and is not influenced by previous TB.

IFN-γ Release Assay Result Is Associated with Disease Site and Death in Active Tuberculosis

RATIONALE

The IFN-γ release assays and tuberculin skin tests are used to support the diagnosis of both latent and active tuberculosis. However, we previously demonstrated that a negative tuberculin test in active tuberculosis is associated with disseminated disease and death. It is unknown whether the same associations exist for IFN-γ release assays.

OBJECTIVES

To determine the association between these tests and site of tuberculosis and death among persons with active tuberculosis.

METHODS

We analyzed IFN-γ release assays and tuberculin test results for all persons with culture-confirmed tuberculosis reported to the U.S. National Tuberculosis Surveillance System from 2010 to 2014. We used logistic regression to calculate the association between these tests and site of disease and death.

MEASUREMENTS AND MAIN RESULTS

A total of 24,803 persons with culture-confirmed tuberculosis had either of these test results available for analysis. Persons with a positive tuberculin test had lower odds of disseminated disease (i.e., miliary or combined pulmonary and extrapulmonary disease), but there was no difference in the odds of disseminated disease with a positive IFN-γ release assay. However, persons who were positive to either of these tests had lower odds of death. An indeterminate IFN-γ release assay result was associated with greater odds of both disseminated disease and death.

CONCLUSIONS

Despite perceived equivalence in clinical practice, IFN-γ release assays and tuberculin test results have different associations with tuberculosis site, yet similar associations with the risk of death. Furthermore, an indeterminate IFN-γ release assay result in a person with active tuberculosis is not unimportant, and rather carries greater odds of disseminated disease and death. Prospective study may improve our understanding of the underlying mechanisms by which these tests are associated with disease localization and death.

Comparison of the Sensitivity of QuantiFERON-TB Gold In-Tube and T-SPOT.TB According to Patient Age

Currently, there are two types of interferon-gamma release assays (IGRAs) in use for the detection of tuberculosis (TB) infection, the QuantiFERON-TB Gold In-Tube test (GFT-GIT) and T-SPOT.TB. Owing to contradictory reports regarding whether the results of these IGRAs are affected by the age of the patient, we aimed to determine if these two tests have age-related differences in sensitivity. We retrospectively reviewed the medical records of diagnosed TB patients who were tested using either QFT-GIT or T-SPOT.TB from February 2008 to December 2013. The positivity of the two tests was analyzed and compared with true TB infection, which was defined as active TB based on either a positive Mycobacterium culture or a positive TB polymerase chain reaction. The QFT-GIT group included 192 TB patients, and the T-SPOT.TB group included 212 TB patients. Of the patients with pulmonary TB, 76 (39.6%) were in the QFT-GIT group and 143 (67.5%) in the T-SPOT.TB group. The overall sensitivity was 80.2% for QFT-GIT and 91.0% for T.SPOT.TB. The sensitivities of QFT-GIT and T-SPOT.TB according to age group were as follows: <29 years, 93.3% and 96.7%; 30-49 years, 86.5% and 94.7%; 50-69 years, 76.8% and 87.5%; and >70 years, 68.3% and 85.7%, respectively. The trend of age-related changes in sensitivity was significant for both QFT-GIT (p = 0.004) and T.SPOT.TB (p = 0.039). However, only QFT-GIT was significantly related to age in the multivariate analysis. QFT-GIT, but not T-SPOT.TB, was significantly affected by patient age.

QuantiFERON-TB Gold Assay on Plasma for Confirmation of Presumed Tuberculosis-Related Uveitis

The QuantiFERON-TB Gold assay was used to measure interferon gamma levels in plasma from 4 patients with presumed tuberculosis-related uveitis before, during, and after antitubercular therapy. After treatment, all patients showed clinical improvement. The concentrations showed a reversion to an absence of interferon gamma in one case, decreased in two cases, and remained stable in one case. These results suggest that the QuantiFERON assay may be useful for tuberculosis-related uveitis diagnosis and follow-up.

Maintenance of Mycobacterium tuberculosis-specific T cell responses in End Stage Renal Disease (ESRD) and implications for diagnostic efficacy

End-stage renal disease (ESRD) patients exhibit elevated risk of tuberculosis (TB) reactivation, but current diagnostics, including the interferon gamma release assay (IGRA), exhibit poor sensitivity in ESRD. We tested 80 ESRD patients and found an 18.75% prevalence of IGRA positivity. A subset of patients was assessed for Mtb-specific expression of 44 cytokines/chemokines, and CD4+ T cell phenotype and function. Similar to non-ESRD IGRA+ individuals, Mtb-specific IFNγ, IL-1RA, IP-10, MCP-3 and IL-2 responses were identified in the ESRD IGRA+ group. 27% of the ESRD IGRA- group exhibited MCP-3 or IL-2 Mtb-specific responses, which may identify cases of latent TB infection in ESRD. Stimulation of PBMC with PPD demonstrated similar CD4+ T cell production of IFNγ, TNFα and GM-CSF by ESRD patients. The reported low sensitivity of the IGRA in ESRD cohorts is therefore unlikely to be due to poor T cell cytokine secretion, and may instead reflect defects in antigen presentation.

Does tuberculosis threaten our ageing populations?

Background

The global population is ageing quickly and our understanding of age-related changes in the immune system suggest that the elderly will have less immunological protection from active tuberculosis (TB).

Discussion

Ongoing global surveillance of TB notifications shows increasing age of patients with active TB. This effect of age is compounded by changes to clinical manifestations of disease, confounding of diagnostic tests and increased rates of adverse reactions to antimicrobial treatment of TB. Future epidemiological surveillance, development of diagnostic tests and trials of treatment shortening should all include a focus on ageing people.

Summary

More detailed surveillance of TB notifications in elderly people should be undertaken and carefully evaluated. Risk stratification will help target care for those in greatest need, particularly those with comorbidities or on immunosuppressive therapies. Novel diagnostics and treatment regimes should be designed specifically to be used in this cohort.

Indirect supportive evidence for diagnosis of tuberculosis-related uveitis: from the tuberculin skin test to the new interferon gamma release assays

PURPOSE

To evaluate clinical and paraclinical parameters for the indirect diagnosis of tuberculosis-related uveitis (TRU).

METHODS

Prospective 2-year study in a tertiary referral centre. Patients with clinically suspected TRU were recruited. Demographical and clinical data were recorded. QuantiFERON(®) -TB Gold (QFT), tuberculosis skin test (TST) and pulmonary X-ray were performed, and other possible uveitis aetiologies were ruled out. Further investigations were also performed case by case after consultation. After final assessment, standard antituberculosis therapy was started if TRU was considered highly probable. Finally, diagnosis of TRU was established according to current criteria and set as gold standard. Strength of association for TRU was determined by odds ratio and compared by appropriate tests. Concordance and binary classification tests were also assessed.

RESULTS

  The study included 103 patients, 54 men and 49 women. Mean age 45.6 years. Sixty-eight patients were Spanish-born and 35 were foreign-born. Final diagnosis included 33 (32%) cases of TRU and 70 (67%) cases with other diagnoses. Asian origin (OR = 3.50, p = 0.046), previous tuberculosis (TB) contact (OR = 2.61, p = 0.026), TB in the past (OR = 6.18, p = 0.004) and associated retinal vasculitis (OR = 7.85, p < 0.001) were significantly related to TRU. Sensitivity (S) and specificity (Sp) of the TST and QFT did not differ significantly (S 87% versus 90% and Sp 85% versus 82%, respectively) with fair agreement (k = 0.607).

CONCLUSION

In a Western urban multi-ethnic population, patients from Asia, TB history or contact in the past and vasculitis are at higher risk of TRU. TST and QF are complementary providing enough S and Sp to support the diagnosis.

Negative effect of smoking on the performance of the QuantiFERON TB gold in tube test

Background

False negative and indeterminate Interferon Gamma Release Assay (IGRA) results are a well documented problem. Cigarette smoking is known to increase the risk of tuberculosis (TB) and to impair Interferon-gamma (IFN-γ) responses to antigenic challenge, but the impact of smoking on IGRA performance is not known. The aim of this study was to evaluate the effect of smoking on IGRA performance in TB patients in a low and high TB prevalence setting respectively.

Methods

Patients with confirmed TB from Denmark (DK, n = 34; 20 smokers) and Tanzania (TZ, n = 172; 23 smokers) were tested with the QuantiFERON-TB Gold In tube (QFT). Median IFN-γ level in smokers and non smokers were compared and smoking was analysed as a risk factor for false negative and indeterminate QFT results.

Results

Smokers from both DK and TZ had lower IFN-γ antigen responses (median 0.9 vs. 4.2 IU/ml, p = 0.04 and 0.4 vs. 1.6, p < 0.01), less positive (50 vs. 86%, p = 0.03 and 48 vs. 75%, p < 0.01) and more false negative (45 vs. 0%, p < 0.01 and 26 vs. 11%, p = 0.04) QFT results. In Tanzanian patients, logistic regression analysis adjusted for sex, age, HIV and alcohol consumption showed an association of smoking with false negative (OR 17.1, CI: 3.0-99.1, p < 0.01) and indeterminate QFT results (OR 5.1, CI: 1.2-21.3, p = 0.02).

Conclusions

Cigarette smoking was associated with false negative and indeterminate IGRA results in both a high and a low TB endemic setting independent of HIV status.

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.