Immunogenicity of the mRNA-1273 COVID-19 vaccine in adult patients with inborn errors of immunity.

BACKGROUND: Patients with inborn errors of immunity (IEI) are at increased risk of severe coronavirus disease-2019 (COVID-19). Effective vaccination against COVID-19 is therefore of great importance in this group, but little is known about the immunogenicity of COVID-19 vaccines in these patients. OBJECTIVES: We sought to study humoral and cellular immune responses after mRNA-1273 COVID-19 vaccination in adult patients with IEI. METHODS: In a prospective, controlled, multicenter study, 505 patients with IEI (common variable immunodeficiency [CVID], isolated or undefined antibody deficiencies, X-linked agammaglobulinemia, combined B- and T-cell immunodeficiency, phagocyte defects) and 192 controls were included. All participants received 2 doses of the mRNA-1273 COVID-19 vaccine. Levels of severe acute respiratory syndrome coronavirus-2-specific binding antibodies, neutralizing antibodies, and T-cell responses were assessed at baseline, 28 days after first vaccination, and 28 days after second vaccination. RESULTS: Seroconversion rates in patients with clinically mild antibody deficiencies and phagocyte defects were similar to those in healthy controls, but seroconversion rates in patients with more severe IEI, such as CVID and combined B- and T-cell immunodeficiency, were lower. Binding antibody titers correlated well to the presence of neutralizing antibodies. T-cell responses were comparable to those in controls in all IEI cohorts, with the exception of patients with CVID. The presence of noninfectious complications and the use of immunosuppressive drugs in patients with CVID were negatively correlated with the antibody response. CONCLUSIONS: COVID-19 vaccination with mRNA-1273 was immunogenic in mild antibody deficiencies and phagocyte defects and in most patients with combined B- and T-cell immunodeficiency and CVID. Lowest response was detected in patients with X-linked agammaglobulinemia and in patients with CVID with noninfectious complications. The assessment of longevity of immune responses in these vulnerable patient groups will guide decision making for additional vaccinations.

Biomarkers to identify Mycobacterium tuberculosis infection among borderline QuantiFERON results.

BACKGROUND: Screening for tuberculosis (TB) infection often includes QuantiFERON-TB Gold Plus (QFT) testing. Previous studies showed that two-thirds of patients with negative QFT results just below the cut-off, so-called borderline test results, nevertheless had other evidence of TB infection. This study aimed to identify a biomarker profile by which borderline QFT results due to TB infection can be distinguished from random test variation. METHODS: QFT supernatants of patients with a borderline (≥0.15 and <0.35 IU·mL-1), low-negative (<0.15 IU·mL-1) or positive (≥0.35 IU·mL-1) QFT result were collected in three hospitals. Bead-based multiplex assays were used to analyse 48 different cytokines, chemokines and growth factors. A prediction model was derived using LASSO regression and applied further to discriminate QFT-positive Mycobacterium tuberculosis-infected patients from borderline QFT patients and QFT-negative patients RESULTS: QFT samples of 195 patients were collected and analysed. Global testing revealed that the levels of 10 kDa interferon (IFN)-γ-induced protein (IP-10/CXCL10), monokine induced by IFN-γ (MIG/CXCL9) and interleukin-1 receptor antagonist in the antigen-stimulated tubes were each significantly higher in patients with a positive QFT result compared with low-negative QFT individuals (p<0.001). A prediction model based on IP-10 and MIG proved highly accurate in discriminating patients with a positive QFT (TB infection) from uninfected individuals with a low-negative QFT (sensitivity 1.00 (95% CI 0.79-1.00) and specificity 0.95 (95% CI 0.74-1.00)). This same model predicted TB infection in 68% of 87 patients with a borderline QFT result. CONCLUSIONS: This study was able to classify borderline QFT results as likely infection-related or random. These findings support additional laboratory testing for either IP-10 or MIG following a borderline QFT result for individuals at increased risk of reactivation TB.

Trends in diagnostic methods and treatment of latent tuberculosis infection in a tertiary care center from 2000 to 2017.

Screening for latent tuberculosis infection (LTBI) is indicated before immunosuppressive therapies but is complicated by lack of a gold standard and limited by, e.g., immunosuppression. This study aimed to investigate a series of patients diagnosed with LTBI during screening before immunosuppressive therapy, describing how the use of diagnostic tests and treatment evolved over time. This retrospective cohort study included all individuals diagnosed with LTBI during screening before intended immunosuppressive therapy in a tertiary care hospital between January 2000 and December 2017. Evidence for LTBI, including history, tuberculin skin test (TST), QuantiFERON (QFT) result and suggestive lesions on chest radiography (CXR), and CT scan if available, was analyzed. The study included 295 individuals with LTBI, with median follow-up of 3.8 years (IQR 1.7-7.4 years). During screening, TST, QFT, and CXR were positive in 80.8%, 53.4%, and 22.7%, respectively. Chest CT revealed lesions associated with past tuberculosis infection in around 70%, significantly more frequent than CXR. In patients diagnosed with LTBI, we observed that the use of TST declined over time whereas the use of QFT increased, and that isoniazid was replaced with rifampicin as preferential treatment. Preventive treatment was started in 82.3%, of whom 88.6% completed treatment. During follow-up, no individuals developed active tuberculosis. The diagnosis of LTBI was based on history, TST, QFT, and/or CXR in nearly every possible combination, but mostly on TST and QFT. The most striking trends were the decreased use of TST, increased use of QFT, and the replacement of isoniazid with rifampicin for treatment.

Tenosynovitis caused by Mycobacterium malmoense in two kidney transplant recipients and review of the literature.

We report two unrelated cases of tenosynovitis caused by Mycobacterium malmoense in kidney transplant recipients. Both patients received immunosuppression and were referred to our tertiary hospital because of persisting complaints lasting >6 months not responding to corticosteroids or surgery. The mycobacterial cultures were positive for the slow-growing M. malmoense after several weeks of incubation. The patient in Case 1 was treated with a combination of surgical debridement and antibiotics, whereas the patient in Case 2 was only treated surgically. Both cases illustrate the doctor's delay in diagnosing mycobacterial infections, and remind us that nontuberculous mycobacterial infections should be part of the differential diagnosis of tenosynovitis, especially in immunocompromised patients.

Role of the QuantiFERON(R)-TB Gold In-Tube assay in screening new immigrants for tuberculosis infection.

This study aimed to estimate the risk of progression to active tuberculosis (TB) within 2 yrs after entry in newly arriving immigrants who were screened with the QuantiFERON®-TB Gold In-Tube assay (QFT-GIT; Cellestis, Carnegie, Australia). In a case-base design, we determined the prevalence QFT-GIT-positive subjects among a representative sample of immigrants aged ≥ 18 yrs who arrived between April 2009 and March 2011 (the base cohort). Active TB patients (cases) within 2 yrs post-arrival in 2005, 2006 or 2007 were extracted from the Netherlands Tuberculosis Register. The risk of progression to active TB was estimated using Bayesian analyses to adjust for the sensitivity of QFT-GIT. Among the base cohort, 20% of 1,468 immigrants were QFT-GIT positive. Stratified by TB incidence in the person's country of origin as low (<100 cases per 100,000 population), intermediate (100-199 cases per 100,000) or high (≥ 200 cases per 100,000), the risk of progression to active TB per 100,000 arriving immigrants if QFT-GIT positive (95% credibility interval) was 456 (95% CI 307-589), 590 (397-762) and 386 (259-499), respectively, compared with 18 (0-46), 38 (0-97) and 28 (0-71) if QFT-GIT negative. Screening newly arriving immigrants with QFT-GIT contributes to detecting those at high risk of subsequent TB reactivation within 2 yrs after entry, which offers opportunities for prevention by targeted interventions.

The risk of tuberculosis in transplant candidates and recipients: a TBNET consensus statement.

Tuberculosis (TB) is a possible complication of solid organ and hematopoietic stem cell transplantation. The identification of candidates for preventive chemotherapy is an effective intervention to protect transplant recipients with latent infection with Mycobacterium tuberculosis from progressing to active disease. The best available proxy for diagnosing latent infection with M. tuberculosis is the identification of an adaptive immune response by the tuberculin skin test or an interferon-γ based ex vivo assay. Risk assessment in transplant recipients for the development of TB depends on, among other factors, the locally expected underlying prevalence of infection with M. tuberculosis in the target population. In areas of high prevalence, preventive chemotherapy for all transplant recipients may be justified without immunodiagnostic testing while in areas of medium and low prevalence, preventive chemotherapy should only be offered to candidates with positive M. tuberculosis-specific immune responses. The diagnosis of TB in transplant recipients can be challenging. Treatment of TB is often difficult due to substantial interactions between anti-TB drugs and immunosuppressive medications. This management guideline summarises current knowledge on the prevention, diagnosis and treatment of TB related to solid organ and hematopoietic stem cell transplantation and provides an expert consensus on questions where scientific evidence is still lacking.

Towards Fixed Dosing of Tocilizumab in ICU-Admitted COVID-19 Patients: Results of an Observational Population Pharmacokinetic and Descriptive Pharmacodynamic Study.

BACKGROUND AND OBJECTIVE: In the randomized controlled trial REMAP-CAP, it was shown that next to dexamethasone, the interleukin (IL)-6 receptor antagonist tocilizumab improves outcome, including survival in intensive care unit (ICU)-admitted coronavirus disease 2019 (COVID)-19 patients. Therefore tocilizumab has been added to many COVID-19 treatment guidelines. Because obesity is a risk factor for the development of severe COVID-19, concerns have been raised about overtreatment, as well as undertreatment, through weight-based dosing of tocilizumab. The currently applied dose of 8 mg/kg is based on the use of this drug for other indications, however it has not formally been investigated for COVID-19. In this study, the pharmacokinetics and pharmacodynamics of tocilizumab were investigated in ICU-admitted COVID-19 patients. METHODS: This was an open-label, single-centre, observational population pharmacokinetic and descriptive pharmacodynamic evaluation study. Enrolled patients, with polymerase chain reaction-confirmed COVID-19 were admitted to the ICU for mechanical ventilation or high flow nasal canula oxygen support. All patients were 18 years of age or older and received intravenous tocilizumab 8 mg/kg (maximum 800 mg) within 24 h after admission to the ICU and received dexamethasone 6 mg daily as concomitant therapy. For evaluation of the pharmacokinetics and pharmacodynamics of tocilizumab, all time points from day 0 to 20 days after dose administration were eligible for collection. A nonlinear mixed-effects model was developed to characterize the population pharmacokinetic parameters of tocilizumab in ICU-admitted COVID-19 patients. Covariate analysis was performed to identify potential covariates for dose individualization. For the development of alternative dosing schedules, Monte Carlo simulations using the final model were performed. RESULTS: Overall, 29 patients were enrolled between 15 December 2020 and 15 March 2021. A total of 139 tocilizumab plasma samples were obtained covering the pharmacokinetic curve of day 0 to day 20 after tocilizumab initiation. A population pharmacokinetic model with parallel linear and nonlinear clearance (CL) was developed and validated. Average CL was estimated to be 0.725 L/day, average volume of distribution (Vd) was 4.34 L, maximum elimination rate (Vmax) was 4.19 µg/day, and concentration at which the elimination pathway is half saturated (Km) was 0.22 µg/mL. Interindividual variability was identified for CL (18.9%) and Vd (21%). Average area under the concentration versus time curve from time zero to infinity of the first dose (AUCinf 1st DOSE) was 938 [±190] µg/mL*days. All patients had tocilizumab exposure above 1 µg/mL for at least 15 days. Bodyweight-based dosing increases variability in exposure compared with fixed dosing. CONCLUSIONS: This study provides evidence to support a fixed dose of tocilizumab 600 mg in COVID-19 patients. Fixed dosing is a safe, logistically attractive, and drug expenses saving alternative compared with the current 8 mg/kg recommendation.

Convalescent Plasma in a Patient with Protracted COVID-19 and Secondary Hypogammaglobulinemia Due to Chronic Lymphocytic Leukemia: Buying Time to Develop Immunity?

It is not exactly clear yet which type of immune response prevails to accomplish viral clearance in coronavirus disease 2019 (COVID-19). Studying a patient with chronic lymphocytic leukemia and hypogammaglobulinemia who suffered from COVID-19 provided insight in the immunological responses after treatment with COVID-19 convalescent plasma (CCP). Treatment consisted of oxygen, repeated glucocorticosteroids and multiple dosages of CCP guided by antibody levels. Retrospectively performed humoral and cellular immunity analysis made clear that not every serological test for COVID-19 is appropriate for follow-up of sufficient neutralizing antibodies after CCP. In retrospect, we think that CCP merely bought time for this patient to develop an adequate cellular immune response which led to viral clearance and ultimately clinical recovery.

Activated PI3Kδ syndrome, an immunodeficiency disorder, leads to sensorimotor deficits recapitulated in a murine model.

The phosphoinositide-3-kinase (PI3K) family plays a major role in cell signaling and is predominant in leukocytes. Gain-of-function (GOF) mutations in the PIK3CD gene lead to the development of activated PI3Kδ syndrome (APDS), a rare primary immunodeficiency disorder. A subset of APDS patients also displays neurodevelopmental delay symptoms, suggesting a potential role of PIK3CD in cognitive and behavioural function. However, the extent and nature of the neurodevelopmental deficits has not been previously quantified. Here, we assessed the cognitive functions of two APDS patients, and investigated the causal role of the PIK3CD GOF mutation in neurological deficits using a murine model of this disease. We used p110δE1020K knock-in mice, harbouring the most common APDS mutation in patients. We found that APDS patients present with visuomotor deficits, exacerbated by autism spectrum disorder comorbidity, whereas p110δE1020K mice exhibited impairments in motor behaviour, learning and repetitive behaviour patterning. Our data indicate that PIK3CD GOF mutations increase the risk for neurodevelopmental deficits, supporting previous findings on the interplay between the nervous and the immune system. Further, our results validate the knock-in mouse model, and offer an objective assessment tool for patients that could be incorporated in diagnosis and in the evaluation of treatments.

Making a Lecture Stick: the Effect of Spaced Instruction on Knowledge Retention in Medical Education.

INTRODUCTION: Poor knowledge retention is a persistent problem among medical students. This challenging issue may be addressed by optimizing frequently used instructional designs, such as lectures. Guided by neuroscientific literature, we designed a spaced learning lecture in which the educator repeats the to-be-learned information using short temporal intervals. We investigated if this modified instructional design could enhance students' retention. MATERIALS AND METHODS: Second-year medical students (n = 148) were randomly allocated to either the spaced lecture or the traditional lecture. The spaced lecture consisted of three 15-min instructional periods, separated by 5-min intervals. A short summary of the preceding information was provided after each interval. The traditional lecture encompassed the same information including the summary in the massed format, thus without the intervals. All students performed a baseline knowledge test 2 weeks prior to the lectures and students' knowledge retention was assessed 8 days after the lectures. RESULTS: The average score on the retention test (α = 0.74) was not significantly different between the spaced lecture group (33.8% ± 13.6%) and the traditional lecture group (31.8% ± 12.9%) after controlling for students' baseline-test performance (F(1,104) = 0.566, p = 0.458). Students' narrative comments showed that the spaced lecture format was well-received and subjectively benefitted their attention-span and cognitive engagement. DISCUSSION AND CONCLUSION: We were unable to show increased knowledge retention after the spaced lecture compared with the traditional lecture. Based on these findings, we provide recommendations for further research. Ultimately, we aim for optimized spaced learning designs to facilitate learning in the medical curriculum and to help educate health professionals with a solid knowledge base.

Cross-reactive immunity to Mycobacterium tuberculosis DosR regulon-encoded antigens in individuals infected with environmental, nontuberculous mycobacteria.

Mycobacterium tuberculosis DosR regulon-encoded antigens are highly immunogenic in M. tuberculosis-infected humans and are associated with latent tuberculosis infection. We have investigated the hypothesis that infection with or exposure to nontuberculous mycobacteria (NTM) can induce cross-reactive immunity to M. tuberculosis DosR regulon-encoded antigens since responsiveness has been observed in non-M. tuberculosis-exposed but purified protein derivative-responsive individuals. M. tuberculosis DosR regulon-encoded antigen-specific T-cell responses were studied in peripheral blood mononuclear cells (PBMCs) of NTM-infected/exposed individuals. BLASTP was used to determine the presence of M. tuberculosis DosR regulon-encoded protein orthologs among environmental mycobacteria and nonmycobacteria. Significant gamma interferon production was observed in PBMCs from NTM-infected/exposed individuals in response to M. tuberculosis DosR regulon-encoded antigens. DosR regulon-encoded protein orthologs were prominently present in tuberculous and environmental mycobacteria and surprisingly also in nonmycobacteria. The ubiquitous presence of the highly conserved DosR master regulator protein Rv3133c suggests that this is a general adaptive bacterial response regulator. We report a first series of M. tuberculosis antigens to which cross-reactive immunity is induced by NTM infection/exposure. The high conservation of M. tuberculosis DosR regulon-encoded antigens most likely enables them to induce cross-reactive T-cell responses.

Diagnosis and treatment of lung infection with nontuberculous mycobacteria.

PURPOSE OF REVIEW: Pulmonary infections caused by nontuberculous mycobacteria (NTM) are diagnosed with increasing frequency, in part due to growing at-risk populations but also as a result of improved awareness and diagnostic facilities. This review summarizes recent literature regarding epidemiological, clinical, diagnostic and therapeutic aspects of NTM lung infections. RECENT FINDINGS: The number of species known to cause NTM infections has increased due to the extended use of molecular techniques. The number of recognized risk factors, including newly discovered inherited immunological disorders and novel types of immunomodulating drugs such as antagonists of tumor necrosis factor-alpha is also growing. Revised diagnostic criteria for NTM lung infection are available but the decision whether to treat a patient remains a matter of careful individual evaluation taking into account the NTM species, extent of disease, general condition and underlying disorders. No major breakthrough has been made with regard to treatment. Antibiotic treatment of NTM infection is complicated by the necessary long duration and the adverse toxicity profile of many of the potentially effective drugs while there is an uncertain correlation between in-vitro susceptibility and in-vivo effectiveness except for two drug-NTM species combinations. The role for novel antibiotics in the treatment of NTM infection is still uncertain. SUMMARY: Much remains unknown regarding treatment of NTM lung infections. In order to provide optimal care, the recommendations provided in the 2007 American Thoracic Society/Infectious Diseases Society of America statement should be taken as a starting point and there should be a low threshold to seek expert consultation.

Radiological Signs of Latent Tuberculosis on Chest Radiography: A Systematic Review and Meta-Analysis.

OBJECTIVE: Current guidelines recommend screening for latent tuberculosis infection (LTBI) with a tuberculin skin test (TST) or interferon gamma release assay (IGRA), or both. Many also recommend chest radiography (CXR), although its added value is uncertain. This systematic review assessed the prevalence of abnormalities suggestive of LTBI on CXR (LTBI-CXR lesions) and evaluated the strength of the association. METHOD: We searched 4 databases up to September 2017 and systematically reviewed cross-sectional and cohort studies reporting LTBI-CXR lesions in individuals with a positive TST or IGRA, or both, result. Prevalence estimates were pooled using random effects models and odds ratios (ORs) were used to calculate risk estimates. RESULTS: In the 26 included studies, the pooled proportion of individuals with LTBI having LTBI-CXR lesions was 0.15 (95% confidence interval [CI], 0.12-0.18]. In 16 studies that reported on individuals with LTBI and uninfected controls, LTBI-CXR lesions were associated with a positive TST result ≥ 5 mm or ≥ 10 mm (OR, 2.45; 95% CI, 1.00-5.99; and OR, 2.06; 95% CI, 1.38-3.09, respectively) and with a positive QuantiFERON result (OR, 1.99; 95% CI, 1.17-3.39) compared to CXR in uninfected controls. Although few studies reported specified lesions, calcified nodules were most frequently reported in individuals with LTBI (proportion, 0.07; 95% CI, 0.02-0.11). CONCLUSIONS: Lesions on CXR suggestive of previous infection with Mycobacterium tuberculosis were significantly associated with positive tests for LTBI, although the sensitivity was only 15%. This finding may have added value when detection of past LTBI is important but immunodiagnostic tests may be unreliable.

Abnormalities suggestive of latent tuberculosis infection on chest radiography; how specific are they?

BACKGROUND: Several radiological features have been reported in association with latent tuberculosis infection (LTBI) but it has not been studied which are specific. The aim of this study was to evaluate allegedly characteristic abnormalities on chest radiography (CXR) in patients with LTBI compared to uninfected controls. METHODS: From 236 patients tested with QuantiFERON-TB Gold In-Tube (QFT), the CXR was re-evaluated in a blinded fashion for fibrotic scarring, (non-)calcified nodules and pleural thickening. LTBI was defined as presence of a positive QFT result and/or positive tuberculin skin test result stratified by Bacille Calmette-Guérin-vaccination status. RESULTS: Any predefined abnormality of LTBI was observed in 116/236 (49.2%) patients, the frequency not being different between groups. However, the specificity for LTBI of a fibrotic scar ≥ 2 cm2 was 100% [95% CI: 92.0%-100%] and of a calcified nodule ≥1.5 mm was 95.7% [95% CI: 85.2%-99.5%]. The frequency of non-calcified nodules and pleural thickening did not differ between groups. CONCLUSION: Only a fibrotic scar ≥ 2 cm2 and/or a calcified nodule ≥1.5 mm were significantly associated with LTBI. This finding is clinically relevant mainly in patients who are at significant risk of TB reactivation and in whom indirect diagnostic tests may be unreliable.

Double-blind randomized Phase I study comparing rdESAT-6 to tuberculin as skin test reagent in the diagnosis of tuberculosis infection.

Limited specificity of the tuberculin skin test incited the development of in vitro assays based on Mycobacterium tuberculosis-specific antigens such as ESAT-6 that are lacking in Bacillus Calmette Guérin (BCG). In animal studies, intradermal ESAT-6 was safe and induced specific skin test responses. The aim of the study was to assess the safety of intradermal recombinant dimer ESAT-6 (rdESAT-6) compared with tuberculin and to determine the human dose. The study design was a double-blind Phase I study with intra-subject randomization to the left and right forearm, comparing 2 Tuberculin Units (TU) intradermal tuberculin (RT23) with 0.01, 0.1, 1 or 10 microg rdESAT-6 in groups of five healthy controls or treated tuberculosis (TB) patients. The risk of sensitization after skin testing was assessed in healthy volunteers. All doses were tolerated well by healthy volunteers and responses to rdESAT-6 were limited to transient redness after 24 h only at the highest dose. No sensitization was observed. Because 1 microg rdESAT-6 induced large responses with local side effects in some TB patients, the 10 microg dose of rdESAT-6 was not tested. Mean responses to 0.01, 0.1 and 1 microg rdESAT-6 measured 14.0, 19.8 and 38.8 mm of redness, respectively, and 7.0, 13.4 and 14.6 mm of induration. The response to tuberculin was similar to the responses to 0.1 microg rdESAT-6. Mild local side effects due to tuberculin and rdESAT-6 were observed in 8/15, respectively, 6/15 patients, more pronounced at the highest rdESAT-6 dose. In conclusion, this pilot Phase I study of safety, feasibility and dose finding of intradermal rdESAT-6 provides proof of principle of a specific skin test for human use. No serious adverse events were observed but the study was not sufficiently powered to demonstrate complete safety. Intradermal rdESAT-6 did not seem to sensitize healthy volunteers. In treated TB patients, responses to rdESAT-6 were optimal at 0.1 microg. Further studies are needed to evaluate sensitization after repeated doses and to study the effect of additional CFP-10 on the sensitivity of a TB-specific skin test.

Borderline QuantiFERON results and the distinction between specific responses and test variability.

BACKGROUND: QuantiFERON (QFT) results near the cut-off are subject to debate. We aimed to investigate which borderline QFT results were due to Mycobacterium tuberculosis (Mtb)-specific responses or to test variability. METHODS: In a contact investigation, tuberculin skin test (TST), QFT and T-SPOT.TB (T-SPOT) were performed in 785 BCG-unvaccinated contacts. Contacts with a low-negative (<0.15), borderline (0.15-0.35), low-positive (0.35-0.70) or high-positive QFT (≥0.70 IU/mL) were compared with respect to exposure, TST and T-SPOT results. Development of active tuberculosis was assessed. RESULTS: Borderline QFT results occurred in threefold excess over test variability (p = 0.0027). In contacts with low-negative, borderline or positive QFT results, a positive TST occurred in 24.9%, 62.1% and 91.4% (p < 0.0001) and a positive T-SPOT result in 6.3%, 41.3% and 86.4%, respectively (p < 0.0001). Two-third (20/29) of contacts with a borderline and 14/16 (88%) with a low-positive QFT had a positive TST and/or T-SPOT, indicating probable Mtb-infection. During 12 years of follow-up, seven patients were diagnosed with active tuberculosis, two of whom after a low-positive QFT. CONCLUSIONS: In this study, most borderline and low-positive QFT results were Mtb-specific, showing the biological significance of a borderline QFT. The clinical relevance, however, will be most distinct in patients who are or will be immunocompromised.