Table 3.
Characteristics of IGRAs.
| Manufacturer | Kit Assay | Method | Antigen (Stimulation Tube) | Coating Plate | Assay Time | Calibrators No. | Dynamic Range | Positivity Criteria | Validity Criteria |
|---|---|---|---|---|---|---|---|---|---|
| Euroimmun | Quan-T-Cell ELISA | ELISA | S1 domain | monoclonal anti-interferon-γ antibody | 3 h 20′ | 6 | 0.5–2000 mIU/mL * | negative: <100 mIU/mL borderline: 100–200 mIU/mL positive: >200 mIU/mL |
BLANK ≤ 400 mIU/mL STIM minus BLANK ≥ 400 mIU/mL |
| SD Bionsensor | STANDARD E Covi-FERON ELISA | ELISA | spike protein antigen derived from SARS-CoV-2 and 20I/501Y.V1 variant (original SP antigen tube), spike protein antigen derived from 20H/501.V2 and 20J/501Y.V3 variants (variant SP antigen tube), nucleocapsid protein antigen (NP Antigen tube) |
monoclonal anti-interferon-γ antibody | Approx. 1 h 40′ | 4 | 0.125~10 IU/mL | Reactive: ≥0.250 IU/mL and ≥25% of Nil value | Nil ≤ 8.0 IU/mL Mitogen ≥ 0.5 IU/mL |
* Dynamic range could vary between batch numbers.