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Antibody to SARS-CoV-2 Nucleocapsid Protein (Serum/Plasma)

Published: August 9, 2026Updated: August 16, 2026

This test detects antibodies in your blood that your immune system produces in response to the SARS-CoV-2 virus, which causes COVID-19. It helps determine if you’ve been exposed to the virus at some point, even if you didn’t get sick.

Quick summary

["This test can help track past infection and guide decisions about immunity or future testing."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
13165-6
Short code
Deprecated S pneum19 Ab Ser-aCnc
Synonyms
Deprecated S pneum19 Ab Ser-aCnc
Category
coagulation
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 Matters

While antibodies may fade over time, they can still provide clues about your immune response to COVID-19. This test is often used alongside other COVID-19 tests to assess exposure history, especially in research or vaccine studies.

How the Test Works

Your blood sample is tested for antibodies specific to the SARS-CoV-2 nucleocapsid protein, a viral component. The test uses an immunoassay method to detect these antibodies, which your immune system creates after exposure.

Sample Collection and Preparation

A blood sample is drawn from your arm, typically in a lab setting. The sample is processed into either serum (after clotting) or plasma (using an anticoagulant), then sent to a lab for testing.

When You Might Need This Test

This test may be recommended if you’ve had a suspected or confirmed COVID-19 infection in the past, if you’re part of a study evaluating immunity, or if your healthcare provider wants to assess past exposure for research purposes.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

COVID-19 Nucleocapsid Antibody

Frequently asked questions

What Does a Positive Result Mean?
A positive result indicates that your immune system has likely encountered the SARS-CoV-2 virus before, meaning you may have had an infection—even if symptoms were mild or absent. However, antibodies can decline over time, so this test is not a guarantee of current immunity.
What Does a Negative Result Mean?
A negative result suggests you either haven’t been exposed to the virus recently or your immune system hasn’t produced detectable antibodies at this time. It doesn’t definitively rule out past exposure, especially if testing was done too soon after infection.
How Long Do Antibodies Last?
Antibodies against SARS-CoV-2 can persist for months or years, but their levels may gradually decrease. Some people develop stronger, longer-lasting immunity, while others may lose detectable antibodies over time. This test is not designed to measure current infection status.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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