Understanding Your Diagnostic Test: What It Is, How It's Done, and Why You May Need It
A blood test that measures the T-cell immune response to SARS-CoV-2 (COVID-19) by detecting gamma interferon release.
{"Measures T-cell immune response to COVID-19","Uses whole blood sample collected by venipuncture","Evaluates cellular immunity beyond antibody testing","Helps assess vaccine effectiveness or prior infection","Performed using immunoassay technique"}
Key facts at a glance
- LOINC
- 98846-9
- Short code
- SARS-CoV-2 T-cell IGRA
- Synonyms
- SARS-CoV-2 IFN-g CD4 cells Bld IA
- Category
- cardiac
- Sample
- whole-blood
- Container
- Lithium heparin tube (green top) or specialized T-cell activation tube (CD-TAH, ACD tube)
- Units
- N/A
- Ref low
- 0
- Ref high
- 10
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 18 years
- Method
- Immunoassay - Interferon Gamma Release Assay (IGRA) following in vitro SARS-CoV-2 antigen stimulation
- CPT
- 86341
- SNOMED
- 897481002
- Specimen volume
- 3-5 mL whole blood
- Stability
- Process within 8-24 hours of collection. Store at room temperature (20-25°C). Do not refrigerate or freeze whole blood.
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 48–72 hours
- Order
- routine
What is this test, and what does it check for in my body?
This test measures how your immune system's T-cells (specifically CD4+ helper T-cells) respond to SARS-CoV-2, the virus that causes COVID-19. It detects gamma interferon (IFN-γ) released by T-cells when they are stimulated by the virus in the laboratory. Unlike antibody tests that measure humoral immunity, this test evaluates cellular immunity, which plays a crucial role in long-term protection against viral infections.
How is this test performed, and what should I expect during the procedure?
A healthcare professional will collect a whole blood sample from a vein in your arm. The blood sample is then sent to a laboratory where it is exposed to SARS-CoV-2 antigens. If your T-cells have been previously exposed to the virus (either from infection or vaccination), they will recognize the antigens and release gamma interferon. This response is measured using a specialized immunoassay technique. The result is corrected for background levels to ensure accuracy.
Why might I need this test, and how will my doctor use the results?
This test may be ordered to: evaluate your immune response after COVID-19 vaccination, determine if you have had a previous SARS-CoV-2 infection (especially if antibody tests are negative), assess the durability of your immune protection, or support clinical research on COVID-19 immune responses. It provides information that complements antibody testing by measuring the cell-mediated portion of your immune system.
Reference range
Result reported as Negative (< 10 AU/mL), Positive (≥ 10 AU/mL), or Indeterminate. Positive results indicate T-cell mediated immune response to SARS-CoV-2 antigens.N/A
No special preparation required. Patient does not need to fast. Inform laboratory if patient has known immunodeficiency or is on immunosuppressive medications. Avoid collection during acute viral illness.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
The SARS-CoV-2 stimulated gamma interferon release test is clinically significant because it measures T-cell-mediated immunity, which is essential for long-term protection against viral infections. This test can detect immune responses in individuals who may have negative antibody results but still have protective T-cell immunity. It is particularly useful for immunocompromised patients who may not mount adequate antibody responses. The test helps healthcare providers understand an individual's immune status beyond what antibody tests reveal, supporting better clinical decision-making regarding vaccination strategies and immunity assessment.
Frequently asked questions
Do I need to fast before this test?
How long does it take to get results?
Does a positive result mean I am immune to COVID-19?
Can this test tell if my vaccine is working?
Is the test safe?
Sources
- 1
- 2
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy