655. Patterns of Interferon-Gamma Release Assay (IGRA) Testing for Tuberculosis in Patients Less Than 2 Years Old

Background The American Academy of Pediatrics recommends use of Interferon-Gamma Release Assays (IGRAs) to diagnose tuberculosis (TB) infection in patients ≥2 years old. However, IGRAs are not currently recommended in younger patients due to limited data and concerns of invalid/indeterminate test results, which occur if there is a positive or negative control failure. We sought to characterize the patterns of IGRA use in clinical practice and results of IGRAs in patients < 2 years old. Methods We conducted a retrospective cohort study of children < 2 years old at two large health systems in the Boston area who had IGRA and/or tuberculin skin test (TST) performed from October 1, 2015 – January 31, 2021. We reviewed medical records to determine IGRA test type, IGRA result (positive, negative, invalid/indeterminate) and location of testing (outpatient primary care, outpatient subspecialty, inpatient). We summarized test interpretability, location, and changes in proportion of IGRA vs. TST. Results We identified 330 IGRA (268 T-SPOT.TB, 62 QuantiFERON Gold) and 2029 TST results among 1982 patients who were < 2 years old (range: 11 days – 1.9 years). Monthly proportion of IGRAs among all TB tests ordered increased from 2015 to 2021 (Figure 1) (Pearson correlation coefficient 0.85, P < 0.001). Among IGRA results, 314 (95%) were negative, 3 (1%) were positive, and 13 (4%) were invalid/indeterminate (11 T-SPOT.TB, 2 QuantiFERON Gold). Of 324 IGRA tests for which testing location was known, 233 (72%) and 91 (28%) were ordered in outpatient and inpatient settings, respectively. Of tests in outpatient settings, 132 (57%) were ordered in primary care offices, 53 (23%) were ordered in subspecialist offices, and 48 (21%) were obtained in outpatient labs of unidentified clinics. Tuberculosis infection tests and proportion IGRA. Total number of tests and proportion of IGRA:TST obtained by month, from October 2015-January 2021. Conclusion While most TB infection tests in this age group were TSTs, the monthly proportion of tests that were IGRAs increased over time between 2015-2021. IGRAs were obtained in varied clinical settings. In this low-burden setting, rates of invalid/indeterminate IGRAs were low among children < 2 years old, which suggests that IGRAs are reasonable TB testing options for patients < 2 years old, and may be preferred given limitations of TSTs. Disclosures Gabriella S. Lamb, MD, MPH, Nothing to disclose

Comparative Evaluation of Standard E TB-Feron ELISA and QuantiFERON-TB Gold Plus Assays in Patients with Tuberculosis and Healthcare Workers

Recently, the American Thoracic Society/Infectious Diseases Society of America/Centers for Disease Control and Prevention advised against performing the interferon-γ-release assay (IGRA) test for individuals with a low risk of TB, and also recommended retesting low-risk individuals with an initial positive IGRA result. However, to evaluate both sensitivity and specificity of available tests, we compared the performance of the Standard E TB-Feron (TBF) and QuantiFERON-TB Gold Plus (QFT-Plus) assays in healthcare workers (HCWs) and tuberculosis (TB) patients. We also retrospectively investigated diabetes mellitus (DM) comorbidity among the enrolled TB patients. We prospectively collected samples from 177 HCWs and 48 TB patients. The TBF and QFT-Plus tests were performed and analyzed according to the manufacturers’ instructions. We also defined IGRA results between 0.2 and 0.7 IU/mL as ‘borderline’. The agreement rate between TBF and QFT-Plus was 92.0% (207/225) with a Cohen’s kappa value of 0.77 (95% CI, 0.68–0.87). While the majority (26/31, 83.9%) of borderline TBF results were in HCWs, the majority (14/19, 73.7%) of borderline QFT-Plus results were in TB patients. Discordant results were found in 18 samples, with TBF-positive/QFT-Plus-negative or indeterminate results in 11 HCWs and seven TB patients. After resampling from 10 HCWs (seven borderline-positive and three positive results, all <1.0), six reverted to negative. The prevalence of DM comorbidity was very high (35.4%). In summary, TBF showed substantial agreement with the QFT-Plus assay but had a higher positivity rate in both HCWs and TB patients. The negative conversion rate was high (60%) among HCWs whose initial (TB Ag-nil) result was <1.0.

The Relationship between Pre-Pandemic Interferon Gamma Release Assay Test Results and COVID-19 Infection: Potential Prognostic Value of Indeterminate IFN-γ Release Assay Results

Objective. To reveal the relationship between interferon-gamma release assay (IGRA) test (Standard ETB-Feron ELISA (TBF)) results performed within 12 months before the COVID-19 pandemic and the frequency of COVID-19 infections and the severity of COVID-19. Methods. The retrospective TBF test results and contact information of 684 patients aged over 18 years who underwent TBF testing between March 11th, 2019, and March 10th, 2020, were obtained. Of the 684 patients contacted by phone, 365 agreed to participate in the study and were enrolled. The patients were divided into three groups (TBF test positive, negative, and indeterminate). The data obtained from the questionnaire were compared statistically. Results. According to the TBF test results, positive (n = 51, 14%), negative (n = 286, 78.3%), and indeterminate (n = 28, 7.7%) groups were compared. The frequency of COVID-19 infections in the indeterminate group was found significantly higher than that in the positive and negative groups ( p = 0.005 ). When the group with COVID-19 (n = 46, 12.6%) was compared with the group without (n = 319, 87.4%), no difference was found in terms of age, sex, body mass index, smoking history and number of cigarettes smoked, TB history, diabetes mellitus, hypertension, coronary artery disease, and biologic and corticosteroid therapy use. Only the frequency of obstructive pulmonary disease was significantly higher in the group without COVID-19 ( p = 0.033 ). Conclusion. The frequency of COVID-19 infection was increased in patients with indeterminate TBF test results. Indeterminate TBF test results may be a guide in terms of risk stratification in groups at risk for COVID-19.

Interferon-gamma release assay levels and risk of progression to active tuberculosis: a systematic review and dose-response meta-regression analysis

Background Identifying and treating individuals with high risk of progression from latent tuberculosis infection to active tuberculosis (TB) disease is critical for eliminating the disease. We aimed to conduct a systematic review and meta-regression analysis to quantify the dose-response relationship between interferon-gamma release assay (IGRA) levels and the risk of progression to active TB. Methods We searched PubMed and Embase from 1 January 2001 to 10 May 2020 for longitudinal studies that reported the risk of progression from latent to active TB as a function of baseline IGRA values. We used a novel Bayesian meta-regression method to pool effect sizes from included studies and generate a continuous dose-response risk curve. Our modeling framework enabled us to incorporate random effects across studies, and include data with different IGRA ranges across studies. The quality of included studies were assessed using the Newcastle-Ottawa scale (NOS). Results We included 34 studies representing 581,956 person-years of follow-up with a total of 788 incident cases of TB in the meta-regression analysis. Higher levels of interferon-gamma were associated with increased risk of progression to active tuberculosis. In the dose-response curve, the risk increased sharply between interferon-gamma levels 0 and 5 IU/ml, after which the risk continued to increase moderately but at a slower pace until reaching about 15 IU/ml where the risk levels off. Compared to 0 IU/ml, the relative risk of progression to active TB among those with interferon-gamma levels of 0.35, 1, 5, 10, 15, and 20 IU/ml were: 1.64 (1.28–2.08), 2.90 (2.02–3.88), 11.38 (6.64–16.38), 19.00 (13.08–26.90), 21.82 (14.65–32.57), and 22.31 (15.43–33.00), respectively. The dose-response relationship remains consistent when limiting the analysis to studies that scored highest in the NOS. Conclusion The current practice of dichotomizing IGRA test results simplifies the TB infection disease continuum. Evaluating IGRA test results over a continuous scale could enable the identification of individuals at greatest risk of progression to active TB.

POS1436 EPIDEMIOLOGY OF LATENT TUBERCULOSIS INFECTION IN PATIENTS WITH RHEUMATIC IMMUNE-MEDIATED DISEASES. SINGLE UNIVERSITY STUDY OF 1117 PATIENTS

Background:Patients with rheumatologic immune-mediated diseases (R-IMID) with Latent tuberculosis infection (LTBI) requiring biologic therapy (BT) are at an increased risk of active tuberculosis (TB). Screening of LTBI with tuberculin skin test (TST) and/or Interferon (IFN)-γ release assays (IGRA) is recommended before starting of BT.Objectives:In patients with R-IMID previously to BT our aim was to assess a) prevalence of LTBI, b) importance of using a booster test in negative TST and c) to compare TST with the IGRA test.Methods:Cross-sectional single University Hospital study including all patients diagnosed with R-IMID who underwent a TST and/or IGRA in the last five years (2016-2020).TST was performed by a subcutaneous injection of 0.1 ml of purified protein derivative (PPD) with a reading after 72 hours. TST was considered positive with an induration of more than 5 mm of diameter. If the first TST was negative, a new TST (Booster) was performed between 1 and 2 weeks after the first TST.LTBI was diagnosed by a positive IGRA and/or TST and absence of active TB (Chest radiograph). Diagnosis with IGRA vs TST was compared (Cohen’s kappa coefficient).Results:We included 1117 patients (741 women/376 men), mean age 53±15 years with LTBI. Chest radiograph was normal in most of the patients, only 39 patients (3.5%) presented signs of previous TB infection, mostly granuloma. Total LTBI prevalence was 31.7% (354/1117). LTBI prevalence in different underlying R-IMID ranges from 35% in vasculitis up to 26.5% in conectivopathies (Figure 1).Booster was positive in 66 patients (7.7%) out of 859 patients with a negative simple TST. Results of TST (+booster) and IGRA tests are shown in Table 1. TST (+booster) was positive in 187 patients (22.9%) out of 817 with a negative or indeterminate IGRA test. IGRA test was positive in 30 (3.8%) out of 793 patients with a negative TST (+booster). Cohen’s Kappa coefficient between TST (+booster) and IGRA (QFT-plus), was 0.381.Conclusion:LTBI is frequent between patients with R-IMID. Booster after negative simple TST may be useful, since it can detect false negatives for LTBI. IGRA and TST(+booster) show a low grade of agreement. Therefore, performing both tests before BT may be recommendable.Table 1.Results of TST (+booster) and IGRA testIGRA (QFT-Plus)PositiveNegativeIndeterminateUnavailableTotalTST(+Booster)Positive891424548324Negative30500130133793Total1196421751811117* Cohen’s kappa coefficient: 0.381Figure 1.Prevalence of LTBI in different underlying R-IMIDLTBI: Latent tuberculosis infection, PsA: Psoriatic arthritis, RA: Rheumatoid arthritis, SpA: Axial spondyloarthritis.Diagnosis of LTBI: Positive TST(+booster) and/or IGRA test.Disclosure of Interests:David Martínez-López: None declared, Joy Osorio-Chavez: None declared, Carmen Álvarez-Reguera: None declared, Virginia Portilla: None declared, Miguel A González-Gay Speakers bureau: Abbvie, Pfizer, Roche, Sanofi and MSD, Consultant of: Abbvie, Pfizer, Roche, Sanofi and MSD, Grant/research support from: Abbvie, MSD, Jansen and Roche, Ricardo Blanco Speakers bureau: Abbvie, Pfizer, Roche, Bristol-Myers, Janssen, Lilly and MSD, Consultant of: Abbvie, Pfizer, Roche, Bristol-Myers, Janssen, Lilly and MSD, Grant/research support from: Abbvie, MSD, and Roche

AB0650 SCREENING TESTS FOR LATENT TUBERCULOSIS OF CANDIDATES TO BIOLOGIC THERAPY: DATA FROM THE TUNISIAN BINAR REGISTRY

Background:The screening and treatment of latent tuberculosis infection (LTBI) is required before starting biologic therapy. Tuberculin skin test (TST) and interferon γ gamma release assay (IGRA) are the two commonly used tests.Objectives:The aim of our study was to analyze data from the Biological National Registry BINAR between 2016 and 2020 in order to compare the diagnostic value of TST and IGRA tests.Methods:We collected data of patients diagnosed with LTBI (having had a TST and/or IGRA before receiving any biotherapy) from the BINAR registry (a National Tunisian registry of patients with inflammatory rheumatic diseases under biologic therapy since less than two years from the inclusion date).Results:From a total of 298 patients included in our study, 199 patients (66.8%) were screened by TST and 159 patients were screened (53.4%) by IGRA.Thirty-four patients (11.4%) had a positive TST and 27 patients (9.1%) had a positive IGRA test.Three patients having negative TST and two having negative IGRA developed tuberculosis.There was no significant difference in our study between these two tests for LTBI diagnosis. The reactivation of tuberculosis can occur even when LTBI screening is negative using TST and IGRA tests.Conclusion:Our results show that the predictive diagnostic value for these two tests is the same. It would be more interesting to practice one of those tests prior to biotherapy.Disclosure of Interests:None declared.

Safety and Immunogenicity of the GamTBvac, the Recombinant Subunit Tuberculosis Vaccine Candidate: A Phase II, Multi-Center, Double-Blind, Randomized, Placebo-Controlled Study

GamTBvac is a candidate tuberculosis vaccine with two fusion proteins, containing Ag85a, ESAT6, CFP10, and a dextran-binding domain (DBD). Phase II of a double-blind, randomized, multicenter, placebo-controlled study in parallel groups in healthy adults to evaluate the safety and immunogenicity of GamTBvac in 180 previously-vaccinated with Bacillus Calmette–Guérin vaccine (BCG) healthy volunteers without Mycobacterium tuberculosis (MTB) infection was conducted. The dose (0.5 mL) of either the study drug or a placebo was administered subcutaneously twice with an 8-week interval. At eight timepoints from 14 to 150 days, whole blood and sera were assayed. Antigen-specific T-cell responses were measured by an in-house interferon-gamma release assay (IGRA-test), the QuantiFERON (QTF) test, and intracellular cytokine staining (ICS). For antibody response detection, the bead-based multiplex immunoassay (MIA) was applied. The vaccine confirmed an acceptable safety profile previously shown in a first-in-human clinical study. After stimulation with both fusions, the highest median level of INF-γ was detected on day 21. The GamTBvac vaccine induced antigen-specific interferon-gamma release, Th1 cytokine-expressing CD4+ T-cells, and IgG responses and results support further clinical testing of GamTBvac.

Development and validation of novel diagnostic nomogram for tuberculous pleurisy based on TB-IGRA results

OBJECTIVE: To establish the diagnostic nomogram for tuberculous pleurisy (TP) based on TB-interferon-gamma release assays (TB-IGRA), as well as clinical and peripheral blood characteristics.MATERIAL AND METHODS: Patients who underwent TB-IGRA tests during hospitalisation and were finally diagnosed, were retrospectively and continuously enrolled. TP was divided into confirmed TP (cTP) and presumptive TP (pTP), and corresponding diagnostic nomograms were established.RESULTS: A total of 1283 patients were enrolled (median age 49 years, range 14–96; males: 63.1%). The area under the curve (AUC) of TB-IGRA was 0.81 (95%CI 0.77–0.84) for cTP (n = 272) and 0.74 (95%CI 0.71–0.78) for pTP (n = 644). The false-positive and negative rates of TB-IGRA among non-TP and cTP were respectively 32.4% and 16.8%. Based on LASSO analysis, we then selected respectively 12 and 10 predictors from clinical and peripheral blood characteristics to establish cTP and pTP nomograms (TB-IGRA was selected). The cTP and pTP nomograms had an AUC of 0.93 (95%CI 0.90–0.95) and 0.92 (95%CI 0.90–0.94) in the training group, and 0.91 (95%CI 0.87–0.96) and 0.93 (95%CI 0.89–0.96) in the validation group, respectively, which were superior to TB-IGRA test alone.CONCLUSION: Novel predictive nomograms with less invasiveness were provided based on TB-IGRA test to assist differential diagnosis of TP and non-TP patients.

Tuberculosis Infection Screening in 5468 Italian Healthcare Students: Investigation of a Borderline Zone Value for the QFT-Test

Healthcare workers are at an increased risk of contracting Mycobacterium tuberculosis infection. Tuberculin skin test (TST) and interferon gamma release assay (IGRA) represent the available tests most used for the diagnosis of latent tuberculosis infection (LTBI). Different borderline zones have been proposed for defining conversions and reversions to improve the interpretation of the IGRA test results as part of serial testing. From 2012 to 2017, 5468 health students of an Italian University Hospital were screened for tuberculosis infection through the execution of the TST and, in case of positivity, of the QuantiFERON-TB® Gold In-Tube assay (QFT–GIT). The QFT–GIT is considered “borderline” with values from 0.35 to 0.99 IU/mL. Among the students who performed the QFT–GIT assay, 27 subjects presented a range of values defined as borderline. The QFT–GIT was repeated after 90 days on 19 subjects with borderline values and showed a negativization of the values in 14 students and a positive conversion in three cases, while for two students, a borderline value was also found for the second test, with a 74% regression of the borderline cases. The introduction of QuantiFERON borderline values is a useful assessment tool to bring out LTBI case candidates for chemoprophylaxis.

An interferon-gamma release assay as a novel biomarker in systemic lupus erythematosus

Objective The mycobacterium tuberculosis (TB) IFN-γ release assay (TB-IGRA) assesses peripheral blood cell release of IFN-γ upon ex vivo exposure to mitogen (IGRA-MT), TB antigen or a negative/nil control (IGRA-NL); IGRA-NL is a measure of spontaneous IFN-γ release (SIR). Here, we investigate the diagnostic associations of elevated SIR and the potential use of IGRA-NL as a novel biomarker in SLE. Methods We analysed diagnostic code frequencies among 11 823 individuals undergoing TB-IGRA testing between 2010 and 2015 in a large urban US health-care system. To study the relationship between IGRA-NL and SLE, we identified 99 individuals with SLE and TB-IGRA test results then assessed correlations between IGRA-NL, normalized IGRA-NL (the quotient of IGRA-NL/IGRA-MT), disease manifestations and disease activity. Results We identified a discovery cohort of 108 individuals with elevated SIR (&gt;5 S.d. above median) that was significantly enriched for a limited set of diagnoses, including SLE, TB infection, haemophagocytic lymphohistiocytosis and HIV infection. In SLE patients undergoing TB-IGRA testing, normalized IGRA-NL correlated better with disease activity than did anti-dsDNA or complement levels. This relationship appeared to reflect interactions between normalized IGRA-NL and the presence of acute skin disease, hypocomplementemia, fever and thrombocytopenia. Conclusion Elevated SIR appears to be associated with a limited number of disease processes, including SLE. The diagnostic utility of SIR remains to be determined. IFN-γ activation, as measured by the TB-IGRA test, may offer a readily available tool for assessing disease activity in patients with SLE.