The IGRA-ELISA and T-SPOT.TB are widely used in China. The aim of the study was to evaluate the performance of the two assays in diagnosis Mycobacterium tuberculosis infection.
Of the 3727 patients ...in the study, 204 underwent testing using both the T-SPOT.TB and IGRA-ELISA, 1794 were tested using the T-SPOT.TB only, and 1729 were tested using the IGRA-ELISA only. The positive rate and consistency of the two assays were analyzed, and their sensitivity and specificity for diagnosing active tuberculosis were compared.
There were no significant differences in the positive rate between the T-SPOT.TB test (25.8%) and IGRA-ELISA (28.6%), p = .065. The two assays were highly consistent, with a kappa value of 0.852 (p < .0001) and a total coincidence rate of 92.7%. For the diagnosis of active tuberculosis, the sensitivity and specificity values of the T-SPOT.TB test were 82.9% (107/129) and 78.6% (1309/1665), respectively, and those of IGRA-ELISA were 81.7% (94/115) and 75.2% (1214/1614), respectively. There were no significant differences in sensitivity (p > .05), but the specificity of the T-SPOT.TB test was slightly higher than that of IGRA-ELISA (p = .023).
Both in terms of diagnosing M. tuberculosis infection and ruling out active tuberculosis, the performance of the IGRA-ELISA—a simple, almost labor-free assay that allows simultaneous processing of a very large number of samples—was well-matched with that of T-SPOT.TB test. However, IGRAs cannot be used as the only test to diagnose active tuberculosis.
•Two IGRAs (T-SPOT.TB test and IGRA-ELISA) were evaluated in the study.•IGRA-ELISA was well-matched with T-SPOT.TB in diagnosing M. tuberculosis infection.•Both T-SPOT.TB test and IGRA-ELISA can be used to rule out active TB.•A cutoff value >300 pg/mL for the IGRA-ELISA or >60 SFCs for T-SPOT.TB test may be reliable to rule in active TB.
Abstract
Background
An immunodiagnostic assay that sensitively detects a cell-mediated immune response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is needed for epidemiological ...investigation and for clinical assessment of T- cell-mediated immune response to vaccines, particularly in the context of emerging variants that might escape antibody responses.
Methods
The performance of a whole blood interferon-gamma (IFN-γ) release assay (IGRA) for the detection of SARS-CoV-2 antigen-specific T cells was evaluated in coronavirus disease 2019 (COVID-19) convalescents tested serially up to 10 months post-infection and in healthy blood donors. SARS-CoV-2 IGRA was applied in contacts of households with index cases. Freshly collected blood in the lithium heparin tube was left unstimulated, stimulated with a SARS-CoV-2 peptide pool, and stimulated with mitogen.
Results
The overall sensitivity and specificity of IGRA were 84.5% (153/181; 95% confidence interval CI: 79.0–89.0) and 86.6% (123/142; 95% CI: 80.0–91.2), respectively. The sensitivity declined from 100% (16/16; 95% CI: 80.6–100) at 0.5-month post-infection to 79.5% (31/39; 95% CI: 64.4–89.2) at 10 months post-infection (P < .01). The IFN-γ response remained relatively robust at 10 months post-infection (3.8 vs 1.3 IU/mL, respectively). In 14 households, IGRA showed a positivity rate of 100% (12/12) and 65.2% (15/23), and IgG of 50.0% (6/12) and 43.5% (10/23) in index cases and contacts, respectively, exhibiting a difference of + 50% (95% CI: +25.4 to +74.6) and +21.7% (95% CI: +9.23 to +42.3), respectively. Either IGRA or IgG was positive in 100% (12/12) of index cases and 73.9% (17/23) of contacts.
Conclusions
The SARS-CoV-2 IGRA is a useful clinical diagnostic tool for assessing cell-mediated immune response to SARS-CoV-2.
SARS-CoV-2 immunodiagnostics are needed to identify infected individuals in order to understand the transmission dynamics of emerging variants and to assess vaccine response. Interferon-gamma release assay maintains sensitivity 10 months post-infection in convalescents and detects more household contacts than IgG.
Comparing the performance of commercially available SARS-CoV-2 T-cell immunoassay responses may provide useful information for future observational or intervention studies as well as to their ...potential customers.
Whole blood was collected from a total of 183 subjects fully vaccinated against COVID-19: 55 healthy controls (Group 1), 50 hematological patients (Group 2), 50 chronic kidney disease patients (Group 3), and 28 elderly nursing home residents (Group 4). Samples were tested with the Roche Elecsys® IGRA (Interferon-gamma release assay) SARS-CoV-2 test (Roche Diagnostics, Rotkreuz, Switzerland), the Euroimmun SARS-CoV-2 test (Euroimmun, Lubeck, Germany), the SARS-CoV-2 T Cell Analysis Kit (Miltenyi Biotec, Bergisch Gladbach, Germany), and a flow-cytometry for intracellular cytokine (IFN-γ) staining-based immunoassay (FC-ICS).
Overall, the Roche Elecsys® assay returned the highest number of positive results (151/179; 84.3%), followed by the Euroimmun test (127/183; 69%), and the FC-ICS (135/179; 75%). The Kappa coefficient of agreement was best between IGRAs (0.64). Most discordant results across assays involved patients from Group 2. Overall, IFN-γ concentrations measured by both IGRAs correlated strongly (rho = 0.78; 95% CI 0.71-0.84; P < 0.001) irrespective of the study group. The frequencies of SARS-CoV-2-reactive IFN-γ T cells and IFN-γ concentrations measured by the IGRAs correlated moderately for CD4
T cells, however, weakly for CD8
T cells. SARS-CoV-2-experienced participants displayed stronger responses than SARS-CoV-2-naïve when IGRAs, rather than FC-ICS, were used.
The SARS-CoV-2 immunoassays evaluated in the present study did not return interchangeable qualitative or quantitative results either in seemingly healthy individuals or in immunosuppressed patients.
Interferon gamma release assays (IGRAs) are used to detect latent Mycobacterium tuberculosis (M.tb) infection (LTBI) in adults, but their performance in older people is not well-established. We ...evaluated IGRAs for LTBI detection in older Hispanic recent TB contacts (ReC) or community controls (CoC).
Cross-sectional assessment of LTBI with T-SPOT.TB and/or QuantiFERON-Gold in-tube or –Plus assay in older (≥60 years) and adult (18–50 years) Hispanic people.
We enrolled 193 CoC (119 adults, 74 older persons) and 459 ReC (361 adults, 98 older persons). LTBI positivity increased with age in CoC (19%–59%, P<0.001), but was similar in ReC (59%–69%, P=0.329). Older people had lower concordance between IGRAs (kappa 0.465 vs 0.688 in adults) and more inconclusive results (indeterminate/borderline 11.6% vs 5.8% in adults, P=0.012). With simultaneous IGRAs, inconclusive results were resolved as positive or negative with the other IGRA. The magnitude of response to M.tb peptides in IGRAs was similar among age groups, but responsiveness to mitogens was lower in older people.
IGRAs are suitable for LTBI detection in older people. Discordant and inconclusive findings are more prevalent in older people, but results are resolved when IGRA is repeated with a different IGRA test.
Abstract
Background
We measured T-cell and antibody responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in vaccinated patients hospitalized for coronavirus disease 2019 ...(COVID-19) and explored their potential value to predict outcomes.
Methods
This was a prospective, longitudinal study including vaccinated patients hospitalized with Delta and Omicron SARS-CoV-2 variants. TrimericS-IgG antibodies and SARS-CoV-2 T-cell response were measured using a specific quantitative interferon-γ release assay (IGRA). Primary outcome was all-cause 28-day mortality or need for intensive care unit (ICU) admission. Cox models were used to assess associations with outcomes.
Results
Of 181 individuals, 158 (87.3%) had detectable SARS-CoV-2 antibodies, 92 (50.8%) showed SARS-CoV-2–specific T-cell responses, and 87 (48.1%) had both responses. Patients who died within 28 days or were admitted to ICU were less likely to have both unspecific and specific T-cell responses in IGRA. In adjusted analyses (adjusted hazard ratio 95% confidence interval), for the entire cohort, having both T-cell and antibody responses at admission (0.16 .05–.58) and Omicron variant (0.38 .17–.87) reduced the hazard of 28-day mortality or ICU admission, whereas higher Charlson comorbidity index score (1.27 1.07–1.51) and lower oxygen saturation to fraction of inspired oxygen ratio (2.36 1.51–3.67) increased the risk.
Conclusions
Preexisting immunity against SARS-CoV-2 is strongly associated with patient outcomes in vaccinated individuals requiring hospital admission for COVID-19. Persons showing both T-cell and antibody responses have the lowest risk of severe outcomes.
In this prospective study of vaccinated patients hospitalized for COVID-19, T-cell immunity against SARS-CoV-2 measured by interferon-γ release assay (IGRA) was strongly associated with patient outcomes. Persons showing both positive antibody test and T-cell responses by IGRA had the lowest risk of mortality.
Authors present a pilot study of the development of innovative flow cytometry-based assay with a potential for use in tuberculosis diagnostics. Currently available tests do not provide robust ...discrimination between latent tuberculosis infection (TBI) and tuberculosis disease (TB). The desired application is to distinguish between the two conditions by evaluating the production of a combination of three cytokines: IL-2 (interleukin-2), IFNɣ (interferon gamma) and TNFɑ (tumor necrosis factor alpha) in CD4+ and CD8+ T cells.
The study was conducted on 68 participants, divided into two arms according to age (paediatric and adults). Each arm was further split into three categories (non-infection (NI), TBI, TB) based on the immune reaction to Mycobacterium tuberculosis (M.tb) after a close contact with pulmonary TB. Each blood sample was stimulated with specific M.tb antigens present in QuantiFERON tubes (TB1 and TB2). We inferred TBI or TB based on the predominant cytokine response of the CD4+ and/or CD8+ T cells.
Significant differences were detected between the NI, TBI and the TB groups in TB1 in the CD4+TNFɑ+parameter in children. Along with IL-2, TNFɑ seems to be the most promising diagnostic marker in both CD4+and CD8+ T cells. However, more detailed analyses on larger cohorts are needed to confirm the observed tendencies.
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•Innovative flow cytometry assay with potential for diagnosing tuberculosis in the clinics.•Differentiation between TB infection and TB disease.•Evaluation of IL-2, IFNɣ and TNFɑ production by CD4+ and CD8+ T cells.
Introduction: Latent tuberculosis infection (LTBI) accounts for almost a quarter of the world population, and, in 5-10% of the subjects with impaired immune-response against M. tuberculosis growth, ...it may progress to active tuberculosis (TB). In this review, we focus on the need to propose a screening for LTBI including preventive therapy offer in rheumatic patients undergoing therapy with biological drugs.
Areas covered: We report on evidence that biologics are associated with an increased risk of active TB reactivation. This effect seems to be mainly limited to treatment with anti-tumor necrosis factor (TNF) agents, while non-anti-TNF-targeted biologics are not likely associated to any increased risk. We introduce the concept that the patients' coexisting host-related risk factors, such as comorbidities, are crucial to identify those at higher risk to reactivate TB. We report that preventive TB therapy is well tolerated in patients treated with biological drugs.
Expert commentary: Availability of non-anti-TNF targeted biologics, that are not associated with an increased risk of TB reactivation, offers a great opportunity to tailor a therapeutic intervention at low/absent TB risk. After proper LTBI screening investigations, preventive TB therapy has been demonstrated to be effective and well-tolerated to reduce the risk of TB reactivation in rheumatic patients requiring biological drugs.
•TSPOT.COVID is an ELISpot interferon gamma-release assay for SARS-CoV-2•TSPOT.COVID identifies a T cell response to SARS-CoV-2 spike S1 and N peptides•2–8 weeks post SARS-CoV-2 diagnosis TSPOT.COVID ...detected 98% of infections•In comparison, immunoglobulin G (IgG) serology detected 83% of infections in the same period•Cellular immune response activated sooner and lasted longer than antibodies
To evaluate the performance of the T-SPOT.COVID test for identifying SARS-CoV-2-responsive T-cells in participants with SARS-CoV-2 infection.
The T-SPOT.COVID test uses ELISpot interferon-gamma release assay (IGRA) methodology to measure T cell responses to SARS-CoV-2 spike S1 and nucleocapsid peptides. T-SPOT.COVID and anti-N immunoglobulin (Ig) G serology tests were performed on blood from 186 patients with nucleic acid amplification test (NAAT)-confirmed-SARS-CoV-2 infection and 100 control group participants.
In the 2–8 weeks after NAAT-diagnosed SARS-CoV-2 infection, the T-SPOT.COVID test detected 98.4% (63 of 64) of infected participants, while anti-N IgG serology detected 82.8%. In the first 2 weeks after diagnosis, during adaptive immune response activation, there were less reactive T-SPOT.COVID responses (75.7%, 28 of 37 infected participants) and many less seropositive responses (32.4%). Response numbers tapered after 8 weeks; however, T-SPOT.COVID test continued to detect most participants with confirmed infection (83.6%, 56 of 67) and continued to out-perform serology (52.2%). T-SPOT.COVID response due to cross-reactive T cells was ruled out by demonstrating that, of 44 control group participants with T cells responsive to 4 human common cold coronavirus peptides, only 1 was T-SPOT.COVID reactive.
The T-SPOT.COVID test performed well in detecting SARS-CoV-2-sensitized T-cells over many months.
Immunosuppression induced by
is important in the pathogenesis of active tuberculosis (TB). However, the impact of depressed TB-specific and non-TB-specific gamma interferon (IFN-γ) response on the ...treatment outcomes of TB patients remains uncertain. In this prospective cohort study, culture- or pathology-proven active TB patients were enrolled and QuantiFERON-TB Gold In-Tube (QFT-GIT) assays were performed before the initiation of anti-TB treatment. TB-specific IFN-γ responses (TB antigen tube subtracted from the nil tube) and non-TB-specific IFN-γ responses (mitogen tube subtracted from the nil tube) were measured and associated with treatment outcomes, including 2-month culture conversion and on-treatment mortality. A total of 212 active TB patients were included in the analysis. We observed a close correlation between decreased lymphocyte count and lower non-TB-specific IFN-γ responses but not TB-specific IFN-γ responses. Patients with lower non-TB-specific IFN-γ responses had lower 2-month culture conversion rate (71.1% versus 84.7%, respectively;
= 0.033) and higher on-treatment mortality (22.6% versus 5.7%, respectively;
= 0.001) than those with higher non-TB-specific IFN-γ responses. In multivariate analysis, depressed non-TB-specific IFN-γ response was an independent factor associated with 2-month sputum culture nonconversion (odds ratio OR, 2.49; 95% CI 95% confidence interval, 1.05 to 5.90) and on-treatment mortality (hazard ratio HR, 2.76; 95% CI, 1.15 to 6.62). In contrast, depressed TB-specific IFN-γ responses were significantly associated with higher on-treatment mortality in univariate analysis but not in multivariate analysis. Our findings suggest that depressed non-TB-specific responses, but not TB-specific IFN-γ responses, as measured by QFT-GIT before the initiation of anti-TB treatment, were significantly associated with worse treatment outcomes in TB patients.
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