Comparison of QuantiFERON-TB Gold In-Tube and QuantiFERON-TB Gold-Plus in the Diagnosis of Mycobacterium tuberculosis Infections in Immunocompromised Patients: a Real-World Study

Evaluation of QuantiFERON TB gold plus among TB household contacts in high incidence settings

BACKGROUND

Accurately identifying and categorizing individuals who are latently infected is critical for developing prevention strategies against tuberculosis (TB) disease. The QuantiFERON-TB Gold Plus (QFT-Plus), a set of two antigen tubes, was used to assess TB household contacts, aiming to induce CD4 + and CD8 + T cell responses.

METHODS

We examined fifty-six TB household contacts for TB infection using the QFT-Plus and QFT-Gold In-Tube (QFT-GIT) tests. In addition, we evaluated 616 samples from the parent study to determine whether there was any association between the QFT-Plus CD8 + T cell responses and variables that were clinically significant. This was done by analyzing the difference in interferon-gamma (IFNγ) levels between TB2 and TB1 tubes. We utilised a cut-off of 0.6 IU/mL.

RESULTS

To assess agreement between tests, a Cohen's kappa of 0.71 was observed across 56 TB contacts. Eight participants reported discordance: four reported positive QFT-Plus and negative QFT-GIT, and four reported negative QFT-Plus and positive QFT-GIT. The QFT-Plus CD8 + T cell responses did not show any significant correlation with the age, sex, history of BCG vaccination, HIV infection, TB risk score and baseline blood draw among adult TB household contacts.

CONCLUSION

The QFT-Plus and QFT-GIT tests significantly agree with one another. No clinically significant variable was observed to be associated with CD8 + T cell responses in QFT-Plus.

Performance comparison of QuantiFERON-TB Gold In-Tube and QuantiFERON-TB Gold Plus in detecting Mycobacterium tuberculosis infection among HIV patients in China

Introduction

No direct comparative study assessing QuantiFERON-TB Gold In-Tube (QFT-GIT) and QuantiFERON-TB Gold Plus (QFT-Plus) for Mycobacterium tuberculosis infection among persons living with HIV (PLHIV) in China has been conducted.

Methods

Simultaneous QFT-GIT and QFT-Plus tests were conducted on PLHIV in a prison hospital. Positivity and negativity results from both assays were compared, and their diagnostic agreement was assessed.

Results

A total of 232 PLHIV individuals were included in this study. Among them, 57 patients (24.6%) and 56 patients (24.1%) were diagnosed with Mycobacterium tuberculosis infection based on QFT-GIT results and QFT-Plus, respectively. The overall agreement between the two assays was 98.3%, with a Cohen's kappa value of 0.954. Consistency rates were observed between QFT-GIT plus, QFT-Plus TB1 and TB2 with QFT-GIT were 98.3%, 97.4% and 97.8%. The IFN-γ levels measured in QFT-GIT were found to surpass those in QFT-Plus TB1 (P = 0.04), while the difference compared to QFT-Plus TB2 exhibited a marginal trend (P = 0.134). Among the subgroup of 52 individuals who underwent dual QFT-GIT tests, a significant proportion of 23.1% (12 individuals) experienced a change in their QFT-GIT results, transitioning from a positive to a negative outcome.

Conclusions

The diagnostic performance of QFT-GIT and QFT-Plus for Mycobacterium tuberculosis infection among PLHIV with relatively higher CD4 counts was found to be comparable. Additionally, our investigation revealed that irrespective of the treatment regimen, whether it involved chemotherapy or immunotherapy, preventive Mycobacterium tuberculosis infection interventions among PLHIV consistently led to a reduction in IFN-γ levels.

Comparative evaluation of QuantiFERON-TB gold in-tube plus for Mycobacterium tuberculosis infection among adolescents in China

BACKGROUND

No head-to-head studies have simultaneously compared the performances of QuantiFERON-TB Gold In-Tube (QFT-GIT), QuantiFERON-TB Gold Plus (QFT-Plus), ESAT6-CFP10 (EC) skin test, and Tuberculin skin test (TST) in adolescents. This study aimed to conduct a comparative assessment of QFT-GIT and QFT-Plus for detecting Mycobacterium tuberculosis(Mtb) infection in high school freshmen.

METHODS

We concurrently administered QFT-GIT, QFT-Plus, EC skin test, and TST to first-year high school students. Blood samples were obtained for the QFT-GIT and QFT-Plus assays before the administration of the EC skin test and TST. The diagnostic values were compared. Discrepancies between the tests were quantified using Cohen's kappa coefficient.

RESULTS

A total of 787 freshmen were recruited in this study. Among 787 subjects, EC was positive in 0.8%, TST in 5.3%, QFT-GIT in 1.1%, and QFT-Plus in 3.2%. Overall agreements for QFT-GIT vs. QFT-Plus, QFT-Plus TB1, and QFT-Plus TB2 were 95.7% (95% CI, 94.0-97.0), 97.3% (95% CI, 95.9-98.3), and 95.9% (95% CI, 94.3-97.2), respectively. Cohen's kappa values were 0.485 (95% CI, 0.319-0.621), 0.593 (95% CI, 0.413-0.744), and 0.451 (95% CI, 0.274-0.600). Consistency rates for QFT-GIT, QFT-Plus, EC skin test, and TST were 96.6% (95% CI, 95.0, 97.0), 92.1% (95% CI, 89.0, 94.0), 94.5% (95% CI, 92.6, 96.1), and 91.2% (95% CI, 88.8, 93.1) with Cohen's kappa values of 0.19 (95% CI, -0.01, 0.38), 0.07 (95% CI, -0.02, 0.19), 0.08 (95% CI, -0.01, 0.23), and 0.12 (95% CI, 0.01, 0.21).

CONCLUSION

The QFT-GIT and QFT-Plus assays exhibited a high level of agreement but demonstrated a moderate correlation. IFN-γ levels measured by both QFT-GIT and QFT-Plus were comparable. Notably, Our study suggests QFT-Plus may detect a higher rate of Mtb infection among high school freshmen compared to QFT-GIT, EC skin test, and TST, though this requires cautious interpretation due to the absence of a gold standard for Mtb infection diagnosis.

A Retrospective Study of Factors Contributing to the Performance of an Interferon-Gamma Release Assay Blood Test for Tuberculosis Infection

BACKGROUND

Tuberculosis (TB) remains a significant global health concern. Accurate detection of latent TB infection is crucial for effective control and prevention. We aimed to assess the performance of an interferon-gamma release assay blood test (QuantiFERON-TB Gold Plus [QFT-Plus]) in various clinical contexts and identify conditions that affect its results.

METHODS

We conducted a retrospective analysis of 31 000 QFT-Plus samples collected from 26 000 subjects at a tertiary hospital in South Korea over a 4-year period and compared the rates of positivity and indeterminate results across diverse clinical situations. We also analysed the contribution of the QuantiFERON TB2 tube to the test's sensitivity and determined optimal cutoff values for 3 hematologic parameters to distinguish false-negative results. These cutoff values were validated in a separate cohort of subjects with microbiologically confirmed subclinical TB.

RESULTS

Rates of QFT-Plus positivity and indeterminate results were disparate across diagnoses. The TB2 tube increased QFT-Plus sensitivity by 4.1% (95% CI, 1.1%-7.0%) in patients with subclinical TB. Absolute lymphocyte count ≤1.19 × 109/L, absolute neutrophil count ≥5.88 × 109/L, and neutrophil-to-lymphocyte ratio ≥4.33 were effective criteria to discriminate false-negative QFT-Plus results. Application of the hematologic criteria, individually or combined with mitogen response <10 IU/mL, substantially improved performance in the main study cohort and the validation cohort.

CONCLUSIONS

These findings highlight the influence of clinical context and patient hematologic profiles on QFT-Plus results. To minimise neglected latent TB infections due to false-negative QFT-Plus results, serial retesting is advisable in patients with severe lymphopenia or neutrophilia, particularly when the mitogen response is <10 IU/mL.

Current status and future landscape of diagnosing tuberculosis infection

Interferon-γ release assays (IGRAs), such as QuantiFERON-TB Gold (QFT) or T-SPOT.TB, are frequently used as tools for the diagnosis of tuberculosis (TB) infection in the 21st century. QFT-Plus recently emerged as the fourth generation of QFT assays and has replaced QFT In-Tube. However, IGRAs have several problems regarding the identification of active, latent, and cured TB infection, and the time-consuming diagnosis of TB infection because of the overnight incubation of clinical specimens or complexity of measuring the level of interferon (IFN)-γ. To easily diagnose TB infection and quickly compare it with conventional IGRAs, many in vitro tests are developed based on assays other than enzyme-linked immunosorbent assay or enzyme-linked immunospot, such as the fluorescent lateral flow assay that requires less manual operation and a shorter time. Simplified versions of IGRAs are emerging, including QIAreach QuantiFERON-TB. On the other hand, to distinguish active TB from latent or cured TB infection, new immunodiagnostic biomarkers beyond IFN-γ are evaluated using QFT supernatants. While IFN-γ or IFN-γ-related chemokine such as IFN-γ induced protein 10 is a potential biomarker in patients with active TB, interleukin-2 or latency-associated antigen such as heparin-binding hemagglutinin may be useful to distinguish active TB from latent or cured TB infection. There are no potential biomarkers to fully distinguish the time-phase of TB infection at present. It is necessary to discover new immunodiagnostic biomarkers to facilitate decisions on treatment selection for active or latent TB infection.

Prevalence and predictors of tuberculosis infection among people living with HIV in a high tuberculosis burden context

BACKGROUND

Tuberculosis (TB) disease is the leading cause of mortality among people living with HIV (PLHIV). Interferon-gamma release assays (IGRAs) are approved for TB infection ascertainment. However, current IGRA data on the prevalence of TB infection in the context of near-universal access to antiretroviral therapy (ART) and TB preventive therapy (TPT) are lacking. We estimated the prevalence and determinants of TB infection among PLHIV within a high TB and HIV burden context.

METHODS

This cross-sectional study included data from adult PLHIV age ≥18 years in whom QuantiFERON-TB Gold Plus (QFT-Plus) assay, an IGRA, was performed. TB infection was defined as a positive or indeterminate QFT-Plus test. Participants with TB and those who had previously used TPT were excluded. Regression analysis was performed to identify independent predictors of TB infection.

RESULTS

Of 121 PLHIV with QFT-Plus test results, females were 74.4% (90/121), and the mean age was 38.4 (SD 10.8) years. Overall, 47.9% (58/121) were classified as TB infection (QFT-Plus test positive and indeterminate results were 39.7% (48/121) and 8.3% (10/121), respectively). Being obese/overweight (body mass index ≥25 kg/m²; p=0.013, adjusted OR (aOR) 2.90, 95% CI 1.25 to 6.74) and ART usage for >3 years (p=0.013, aOR 3.99, 95% CI 1.55 to 10.28) were independently associated with TB infection.

CONCLUSION

There was a high TB infection prevalence among PLHIV. A longer period of ART and obesity were independently associated with TB infection. The relationship between obesity/overweight and TB infection may be related to ART use and immune reconstitution and requires further investigation. Given the known benefit of test-directed TPT among PLHIV never exposed to TPT, its clinical and cost implications for low and middle-income countries should be explored further.

TBC and COVID: an interplay between two infections

INTRODUCTION

In a historical era dominated by the SARS-CoV-2 pandemic, a fact of growing interest emerges regarding co-infection with Mycobacterium tuberculosis (M. tuberculosis). This represents today an important clinical and diagnostic challenge, as the two pathogens are capable, through specific immunopathological mechanisms, of interacting with each other, determining a severe respiratory condition with a severe prognosis.

AREAS COVERED

With this review, we wanted to collect and analyze the latest scientific evidence concerning the main immunopathogenetic mechanisms shared by these two respiratory pathogens, with particular interest in the possible iatrogenic factors favoring coinfection and the need to define multidisciplinary and standardized screening tools aimed to identify coinfection early, ensuring the best clinical and therapeutic management.

EXPERT OPINION

The existence of a direct immunopathogenetic link between COVID-19 and TB indirectly contributes to mutual morbidity and mortality. The identification and application of early and standardized screening tools aimed at the identification of this condition is essential, in addition to vaccine prevention.

Prevalence of Latent Tuberculosis Infection among Patients Undergoing Regular Hemodialysis in Disenfranchised Communities: A Multicenter Study during COVID-19 Pandemic

Background and Objectives: Due to their weakened immune response, hemodialysis (HD) patients with latent tuberculosis infection (LTBI) are at higher risk for active tuberculosis (TB) disease and are more subject to patient-to-patient transmission within dialysis units. Consequently, current guidelines advocate screening these patients for LTBI. To our knowledge, the epidemiology of LTBI in HD patients has never been examined before in Lebanon. In this context, this study aimed to determine LTBI prevalence among patients undergoing regular HD in Northern Lebanon and to identify potential factors associated with this infection. Notably, the study was conducted during the COVID-19 pandemic, which is likely to have catastrophic effects on TB and increase the risk of mortality and hospitalization in HD patients. Materials and Methods: A multicenter cross-sectional study was carried out in three hospital dialysis units in Tripoli, North Lebanon. Blood samples and sociodemographic and clinical data were collected from 93 HD patients. To screen for LTBI, all patient samples underwent the fourth-generation QuantiFERON-TB Gold Plus assay (QFT-Plus). Multivariable logistic regression analysis was used to identify the predictors of LTBI status in HD patients. Results: Overall, 51 men and 42 women were enrolled. The mean age of the study population was 58.3 ± 12.4 years. Nine HD patients had indeterminate QFT-Plus results and were therefore excluded from subsequent statistical analysis. Among the remaining 84 participants with valid results, QFT-Plus was positive in 16 patients, showing a positivity prevalence of 19% (95% interval for p: 11.3%, 29.1%). Multivariable logistic regression analysis showed that LTBI was significantly associated with age [OR = 1.06; 95% CI = 1.01 to 1.13; p = 0.03] and a low-income level [OR = 9.29; 95% CI = 1.62 to 178; p = 0.04]. Conclusion: LTBI was found to be prevalent in one in five HD patients examined in our study. Therefore, effective TB control measures need to be implemented in this vulnerable population, with special attention to elderly patients with low socioeconomic status.

Comparing the diagnostic performance of QuantiFERON-TB Gold Plus with QFT-GIT, T-SPOT.TB and TST: a systematic review and meta-analysis

BACKGROUND

QuantiFERON-TB Gold Plus (QFT-Plus) is an important test that has emerged in recent years for detecting TB infection. We conducted a review to compare the sensitivity, specificity and positive rate of QFT-Plus with that of QuantiFERON-TB Gold In-Tube (QFT-GIT), T-cell spot of tuberculosis assay (T-SPOT.TB) and Tuberculin test (TST).

METHODS

PubMed and Embase were searched, without language restrictions, from 1 January 2015 to 31 March 2022 using "Mycobacterium tuberculosis Infections" and "QuantiFERON-TB-Plus" as search phrases. We estimated the sensitivity from studies of patients with active tuberculosis, specificity from studies of populations with very low risk of TB exposure, and positive rate from studies of high-risk populations. The methodological quality of the eligible studies was assessed, and a random-effects model meta-analysis was used to determine the risk difference (RD). We assessed the pooled rate by using a random-effects model. This study was registered in PROSPERO (CRD 42021267432).

RESULTS

Of 3996 studies, 83 were eligible for full-text screening and 41 were included in the meta-analysis. In patients with active TB, the sensitivity of QFT-Plus was compared to that of QFT-GIT and T-SPOT.TB, respectively, and no statistically differences were found. In populations with a very low risk of TB exposure, the specificity of QFT-Plus was compared with that of QFT-GTI and T-SPOT.TB, respectively, and no statistically differences were found. Two studies were eligible to compare the specificity of the QFT-Plus test with that of the TST test, and the pooled RD was 0.12 (95% CI 0.02 to 0.22). In high-risk populations, 18 studies were eligible to compare the positive rate of the QFT-Plus test with that of the QFT-GIT test, and the pooled RD was 0.02 (95% CI 0.01 to 0.03). The positive rate of QFT-Plus was compared with that of T-SPOT.TB and TST groups, and no statistically differences were found.

CONCLUSIONS

The diagnostic performance of QFT-Plus was similar to that of QFT-GIT and T-SPOT.TB, but was slightly more specific than TST.

Clinical Characteristics and Outcomes in Chronic Kidney Disease Patients with Tuberculosis in China: A Retrospective Cohort Study

Background

The diverse manifestations of tuberculosis (TB) in chronic kidney disease (CKD) patients can cause difficulty in diagnosis, delayed treatment, even death. Therefore, this study investigated the clinical characteristics and the risk factors for mortality in CKD patients with TB.

Methods

This retrospective study included 167 patients diagnosed with active TB at two tertiary medical centers in Chongqing within six years. Clinical characteristics and outcomes of anti-TB treatment in patients with and without CKD were collected, and the predictive mortality values of variables were analyzed.

Results

Of the 167 patients, 66.7% (44/66) hemodialysis (HD), 41.1% (21/51) pre-HD, and 32.0% (16/50) non-CKD patients had extrapulmonary TB. The pleura and lymph node were the common sites in CKD patients. Clinical presentations of cough and hemoptysis in CKD patients were less common than those in non-CKD patients, 13.7% (16/117) of CKD patients even not having any clinical symptoms. The positive rates of tuberculin skin test, TB-polymerase chain reaction and acid-fast bacilli in sputum in HD patients were lower than those in pre-HD and non-CKD patients (p<0.05). CKD patients were more prone to gastrointestinal and neurological side effects during anti-TB treatment. The mortality rates of non-CKD, pre-HD and HD patients was 6.1%, 31.9% and 37.3%, respectively. Multivariate Cox analysis revealed that age≥40 years (HR: 5.871; p=0.019), hypoalbuminemia (HR:2.879; p=0.004), CKD stage 4–5 (HR:4.719; p=0.018) and HD (HR:6.13; p=0.005) were associated with mortality.

Discussion

CKD patients with TB have atypical clinical manifestations and high mortality. Age, hypoalbuminemia, CKD stage 4–5, and HD were independent predictors of mortality.

Evaluation of tuberculosis diagnostic biomarkers in immunocompromised hosts based on cytokine levels in QuantiFERON-TB Gold Plus

Tuberculosis (TB) remains a serious health concern globally. QuantiFERON-TB (QFT) is a diagnostic tool for TB detection, and its sensitivity is reduced in immunocompromised hosts with low T lymphocyte counts or abnormal T cell function. This study aimed to evaluate the correlation between T cell and cytokine levels in patients with active TB using QFT-Plus. Forty-five patients with active TB were enrolled, and the cytokines in QFT-Plus tube supernatants were quantified using the MAGPIX System. CD4⁺ T cell count negatively correlated with patient age (p < 0.001, r = -0.51). The levels of TB1-responsive interleukin-1 receptor antagonist (IL-1Ra) and IL-2 correlated with CD4⁺ T cell count, whereas the levels of TB2-responsive IL-1Ra and IFN-γ-induced protein 10 correlated with both CD4⁺ and CD8⁺ T cell counts. Cytokines that correlated with CD4⁺ and CD8⁺ T cell counts might not be suitable TB diagnostic biomarkers in immunocompromised hosts. Notably, cytokines that did not correlate with the T cell counts, such as monocyte chemoattractant protein-1, might be candidate biomarkers for TB in immunocompromised hosts. Our findings might help improve TB diagnosis, which could enable prompt treatment and minimize poor disease outcomes.