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

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

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 did not experience symptoms.

Quick summary

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

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

Key facts at a glance

LOINC
13159-9
Short code
Deprecated S pneum19 Ab sp1 Ser-aCnc
Synonyms
Deprecated S pneum19 Ab sp1 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 Might Be Ordered

Your healthcare provider may recommend this test if you suspect you’ve had COVID-19 but test results for active infection (such as PCR or antigen tests) are unclear. It can also be used in research or screening contexts where past exposure is suspected.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample, typically drawn from a vein in your arm. The sample is processed to check for antibodies against the virus’s nucleocapsid protein.

What the Test Results Mean

Positive results indicate the presence of antibodies, suggesting your immune system has likely encountered the virus. Negative results mean no detectable antibodies were found at this time, which does not definitively rule out past infection.

Common Uses and Limitations

This test is often used alongside other COVID-19 tests (like PCR or antigen tests) to confirm or clarify infection status. It cannot distinguish between infections from different variants or confirm recent exposure.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

SARS-CoV-2 Nucleocapsid Antibody (Serum)

Frequently asked questions

What does a positive result mean?
A positive result means your blood contains antibodies that likely developed after exposure to the virus. This does not confirm active infection but indicates your immune system has recognized the virus. It may help guide future testing or vaccination strategies.
Can this test detect recent COVID-19 infection?
No, this test detects antibodies formed after infection, not active virus. For recent infection, you would need a PCR or antigen test instead.
Why might my healthcare provider order this test?
Your provider may order this test if you have symptoms suggestive of past infection, if you’ve been exposed to COVID-19, or if you’re part of a study evaluating immunity. It helps assess whether your immune response has been activated.
  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