Serum or Plasma Anti-SARS-CoV-2 Nucleocapsid Antibody, Qualitative (IgG)
This test checks for antibodies against the SARS-CoV-2 virus’s nucleocapsid protein, which your immune system may produce after infection with COVID-19. It helps determine if you’ve been exposed to the virus, even if you didn’t develop symptoms.
["This test may help confirm past COVID-19 infection, even if you were asymptomatic."]
Key facts at a glance
- LOINC
- 63548-2
- Short code
- ENA SM-B Ab Ser IA-aCnc
- Synonyms
- ENA SM-B Ab Ser IA-aCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- ia
- 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
What This Test Measures
The nucleocapsid protein is a key structural component of the SARS-CoV-2 virus. If your body detects this protein, your immune system may produce antibodies (IgG) to fight it. This test detects these antibodies in your serum or plasma to indicate whether you’ve had an immune response to the virus.
Why It’s Done
Doctors may order this test to assess past COVID-19 infection, especially in cases where symptoms were mild or absent. It can also help evaluate immune response in individuals who tested positive for SARS-CoV-2 but no longer have detectable viral RNA (e.g., via PCR).
When to Expect Results
Results may take several days to a week to process, depending on lab workload. Follow-up with your healthcare provider for interpretation.
What to Expect Before the Test
No special preparation is needed. You may have a simple blood draw from a vein in your arm. If you’re concerned about discomfort, let your provider know.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Positive results suggest past infection with SARS-CoV-2, meaning your body has developed antibodies against the virus. This can be useful for monitoring immunity, research studies, or determining eligibility for certain vaccines or treatments. However, antibodies may wane over time, so results should be interpreted in context with clinical history and other tests.
Short name
Anti-Nucleocapsid Antibody (IgG)
Frequently asked questions
Will this test show if I currently have COVID-19?
How long do antibodies last after infection?
Can this test be used to confirm vaccine immunity?
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