Antibody to SARS-CoV-2 Nucleocapsid Protein (Serum)
This test detects antibodies in your blood that may have developed in response to exposure to the SARS-CoV-2 virus, which causes COVID-19. It helps determine if your immune system has recognized and fought the virus, even if you had no symptoms.
["Assesses past exposure to COVID-19 through antibody presence."]
Key facts at a glance
- LOINC
- 49804-8
- Short code
- Deprecated S pneum19 Ab sp1 Ser IA-aCnc
- Synonyms
- Deprecated S pneum19 Ab sp1 Ser IA-aCnc
- Category
- coagulation
- 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 test looks for antibodies called immunoglobulin G (IgG) and sometimes immunoglobulin M (IgM) against the nucleocapsid protein of the SARS-CoV-2 virus. These antibodies are part of your immune response and can appear after infection, even if symptoms were mild or absent. This test is often used to confirm past infection rather than active illness.
Why It Might Be Ordered
Your healthcare provider may order this test if you had COVID-19 symptoms, were exposed to someone with COVID-19, or if you’re part of a study or surveillance program tracking antibody responses. It can also help determine immunity status for travel, work, or vaccination purposes.
How the Test Works
A blood sample is drawn from your arm. The serum (liquid part of blood without clots) is then tested in a lab using an immunoassay method to detect specific antibodies against the virus’s nucleocapsid protein. The result indicates whether your immune system has produced these antibodies.
What the Results Mean
A positive result means your body has likely been exposed to the virus and developed antibodies. A negative result suggests no detectable antibodies were found, which may mean you were never infected or the test was taken too early. Results can vary based on timing since exposure and individual immune response.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Antibody presence can indicate immunity from past infection, but it does not guarantee protection against future infection. Antibody levels may decline over time, and some people may not develop detectable antibodies. This test is not used to diagnose active COVID-19 or replace other diagnostic tools like PCR tests.
Short name
COVID-19 Nucleocapsid Antibody (Serum)
Frequently asked questions
When Might I Get False Results?
How Long Do Antibodies Last?
Does This Test Replace a COVID-19 PCR Test?
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