Elecsys® IGRA SARS-CoV-2

Immunoassay for the qualitative detection of T cell-mediated immune response to SARS-CoV-2

Elecsys® IGRA SARS-CoV-2
Immunoassay for the qualitative detection of T cell-mediated immune response to SARS-CoV-2

Elecsys® IGRA SARS-CoV-2 test was developed as an aid in identifying individuals with an adaptive T cell response to SARS-CoV-2, indicative of past exposure to the virus or COVID-19 vaccination. By that, it provides the physicians valuable information on the T cell responses of the patient, enabling them to make better-informed decisions for patient care.

Together with other diagnostic and serological assays, Elecsys® IGRA SARS-CoV-2 represents a complementary tool that allows physicians to have a comprehensive picture of the immune status of patients. 


Elecsys® IGRA SARS-CoV-2 assay characteristics

The Elecsys® IGRA SARS-CoV-2 test combines the cobas® IGRA SARS-CoV-2 Tubes for in vitro T cell stimulation and an automated electrochemiluminescence immunoassay (“ECLIA”) for interferon gamma measurement, to qualitatively detect T cell-mediated immune response to SARS-CoV-2 in human whole blood. Using 189 different SARS-CoV-2 antigens with a broad coverage of the viral genome and host HLA subtypes, the assay is designed for robustness against viral variants and population diversity.

Elecsys® IGRA SARS-CoV-2

  • Systems

    cobas e 411 analyzer, cobas e 601/602 units, and cobas e 402 / cobas e 801 analytical modules

  • Testing Time

    T cell stimulation: 16-24h; ECLIA IFN-γ: 18 minutes

  • Test principle

    Two steps: 1. T cell stimulation with SARS-CoV-2 peptides; 2. Automated ECLIA immunoassay for IFN-γ measurement (Double antibody sandwich assay)

  • Calibration

    2-point calibration

  • Traceability

    Standardized against the first British INTERFERON GAMMA (HUMAN, LEUKOCYTE-DERIVED) NIBSC code: 82/587

  • Quality control (samples)

    NC tube: negative control (IFN-γ base line levels), PC tube: positive control (T cell fitness)

  • Quality control (ECLIA IFN-γ)

    PreciControl Interferon Gamma




  • Specimen types

    T cell stimulation: Human whole blood (collected in Li-Heparin tubes or cobas® IGRA SARS-CoV-2 Tubes); ECLIA IFN-γ: plasma*

  • Sample volume

    T cell stimulation: 3 × 1.2 mL; ECLIA IFN-γ: 30µL** / 18µL***

  • Onboard stability

    14 days

  • Intermediate precision**

    cobas e 411: CV 2.5–5.1%; cobas e 601/602: CV 2.5–3.4%; cobas e 402/801: 1.4–1.9%

* Resulting after centrifugation of whole blood after T cell stimulation. ** In plasma samples containing IFN-γ (~0.4 - 90 IU/mL)

** on the cobas e 411 analyzer and the cobas e 601 / 602 modules; *** on the cobas e 801 and cobas e 402 analytical units

Elecsys® IGRA SARS-CoV-2 (Mat. No. 09542477190, 09542485190) method sheets, V1 2022-06.

Elecsys® IGRA SARS-CoV-2 test principle


The Elecsys® IGRA SARS‐CoV‐2 test includes two major steps:

Step 1: ex-vivo / in vitro stimulation of patient T cells with pathogen specific peptides to generate production of interferon gamma indicating a previous contact of the patient with the pathogen - this phase takes place in the cobas® IGRA SARS-CoV-2 Tubes filled with patient whole blood.

Step 2: interferon gamma read out in the plasma extracted from the cobas® IGRA SARS-CoV-2 Tubes after incubation and centrifugation. Such read out will be performed on the cobas platforms with the Elecsys® IGRA SARS-CoV-2 immunoassay.

Elecsys® IGRA SARS-CoV-2

A stimulation phase using SARS-CoV-2 antigens in the cobas® IGRA SARS-CoV-2 tubes 


Whole blood

An automated ECLIA IFN-γ readout to qualitatively detect in vitro the patient T cell-mediated immune response to SARS-CoV-2



Process T cells in sample are stimulated by SARS-CoV-2 specific peptides. Activated SARS-CoV-2 specific T cells release IFN-γ as a result. IFN-γ levels are measured and result from the different tubes are combined for the final interpretation, so that the presence of IFN-γ released by SARS-CoV-2 specific cells is determined.
Sample Whole blood (heparinized) Plasma
Incubation Time 16–24h 18min
Specific for SARS-CoV-2 Yes No
Manufacturer LG Chem (3rd party) Roche

The Elecsys® IGRA SARS-CoV-2 solution comprises two types of reagents:

  • cobas® IGRA SARS-CoV-2 Tubes
  • Elecsys® IGRA SARS-CoV-2 immunoassay

T cell collection tubes - Combining the results of 3 individual tubes per patient

Positive control (PC) Tube

Confirmation of sample quality (T cell fitness and stimulation potential)

Positive control (PC)
  • Tube coated with mitogen (generic, non-pathogen specific T cell activator)
  • Value above a minimum threshold

Negative control (NC) tube

Determination of baseline IFN-γ levels in blood

Negative control (NC)
  • No activating components coated inside tube
  • Value below a maximum threshold

Antigen (Ag) Tube

Determination of IFN-γ released upon stimulation with SARS-CoV-2 peptides

Antigen tube (PC)
  • Ag test tube coated with SARS-CoV-2 unique peptides (≈ 200)
  • Only T cells that recognize and bind to the specific SARS-CoV-2 viral antigens (reactive T cells) will secrete IFN-γ
  • No specific threshold

The Elecsys®  IGRA SARS-CoV-2 immunoassay is a ready-to-use reagent pack for interferon gamma read-out. The module is calibrated and controlled with a negative and positive calibrator and control, respectively. The PreciControl Interferon Gamma (PC1:  negative; PC2: IFN Gamma positive) is launched together with the Elecsys® IGRA SARS-CoV-2 immunoassay.