Immunoassay for Anti-SARS-CoV-2 Nucleocapsid Antibodies (Serum/Plasma)
This test detects antibodies against the SARS-CoV-2 virus’s nucleocapsid protein, which your immune system produces after infection with COVID-19. It helps confirm past infection, even if symptoms were mild or absent.
["This test checks for immunity markers from a previous COVID-19 infection, not current illness."]
Key facts at a glance
- LOINC
- 14025-1
- Short code
- HTLV I+II p36 Ab Ser Ql IB
- Synonyms
- HTLV I+II p36 Ab Ser Ql IB
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- ib
- 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 Does This Test Measure?
The test measures the presence of antibodies (specifically IgG) that target the nucleocapsid protein of SARS-CoV-2. These antibodies develop after your body has encountered the virus, typically within 1–3 weeks after infection. This is a qualitative test, meaning it only tells you if antibodies are present or not, not the exact amount.
Why Might You Need This Test?
Healthcare providers may order this test to determine if you’ve had COVID-19, even if you didn’t show symptoms. It’s useful for screening after exposure, evaluating vaccine responses, or assessing immunity in high-risk groups.
How Is the Test Performed?
A blood sample is taken from a vein in your arm. The serum or plasma is then tested using an immunoassay method to detect antibodies. Results are typically ready within 24–48 hours.
What Are Possible Results?
A **positive** result indicates the presence of antibodies, suggesting a past SARS-CoV-2 infection. A **negative** result means no detectable antibodies were found, but this doesn’t rule out infection if tested too early. False negatives can occur if tested before antibody development.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Positive results confirm past infection and may indicate immunity, though antibody levels can wane over time. Negative results alone don’t confirm no infection—retesting later may be needed. This test is not for diagnosing active COVID-19 or monitoring current illness. Always discuss results with your healthcare provider for guidance.
Short name
Anti-Nucleocapsid Antibody Test
Frequently asked questions
When Should I Expect Results?
What If My Test Is Negative but I Suspect I Had COVID-19?
Does This Test Differentiate Between Vaccine and Natural Infection?
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