Anti-SARS-CoV-2 IgG and IgA Nucleocapsid Protein Antibody Test (Serum/Plasma)
This test detects antibodies (IgG and IgA) against the SARS-CoV-2 virus’s nucleocapsid protein, which your immune system produces after infection or vaccination. It helps determine if you’ve been exposed to COVID-19.
["This test checks for immunity to COVID-19 by measuring specific antibodies in your blood."]
Key facts at a glance
- LOINC
- 99771-8
- Short code
- SARS-CoV-2 IGRA Spk+Nuclcp Pnl Bld
- Synonyms
- SARS-CoV-2 IGRA Spk+Nuclcp Pnl Bld
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why This Test Is Done
Your healthcare provider may order this test to assess immunity status after vaccination, evaluate past infection history, or guide decisions about exposure risk. It’s often used in screening or confirmation settings for COVID-19.
The test uses an immunoassay method to detect antibodies (IgG and IgA) against the virus’s nucleocapsid protein. IgG antibodies typically appear weeks to months after infection or vaccination and last longer, while IgA may appear earlier but is less durable.
IgG antibodies indicate long-term immunity, while IgA may reflect recent exposure or early immune response. Both together provide a more complete picture of your immune system’s reaction.
What to Expect Before the Test
No special preparation is needed. You’ll provide a blood sample (serum or plasma) via venipuncture or fingerstick. If testing urine or saliva, follow your provider’s instructions for sample collection.
What the Results Mean
Positive results suggest you’ve been infected or vaccinated and developed antibodies. Negative results mean no detectable antibodies were found at this time. Results may vary by test type (screen vs. confirm).
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: This test helps determine immunity status for vaccination recommendations, travel clearance, or workplace safety. IgG positivity often correlates with protection, while IgA may indicate recent exposure. Results guide decisions about retesting or booster timing.
Short name
SARS-CoV-2 Antibody Panel (Screen/Confirm)
Frequently asked questions
How long does it take to get results from this test?
Can I get this test if I’m not vaccinated?
What if my results are negative but I suspect I had COVID-19?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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