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

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

This test checks for antibodies in your blood that may have developed after exposure to the virus responsible for COVID-19. Antibodies can help your immune system recognize and fight the virus.

Quick summary

["This test helps determine if you’ve had an infection with the COVID-19 virus in the past."]

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

Key facts at a glance

LOINC
27148-6
Short code
Deprecated S pneum19 Ab sp1 Ser-mCnc
Synonyms
Deprecated S pneum19 Ab sp1 Ser-mCnc
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

What Does This Test Measure?

The test detects antibodies specific to the nucleocapsid protein of SARS-CoV-2, a virus that causes COVID-19. These antibodies are part of your immune response and can appear after infection, even if you had mild or no symptoms.

Why Might You Need This Test?

Healthcare providers may order this test to confirm past infection, assess immune response, or evaluate exposure history—especially in situations where testing for active infection (like PCR or antigen tests) isn’t available or practical.

How Is This Test Performed?

A blood sample is taken from a vein in your arm. The sample is then analyzed in a lab to detect the presence of antibodies against the virus’s nucleocapsid protein.

What Are the Results Typically Used For?

Results may help guide decisions about vaccination, immune response evaluation, or understanding past exposure, though they do not confirm current infection. Positive results suggest prior exposure, but they do not replace testing for active illness.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

COVID-19 Nucleocapsid Antibody Test

Frequently asked questions

How long after infection might antibodies appear?
Antibodies to the nucleocapsid protein can begin appearing in the blood within about 10 to 14 days after infection, though they may take longer to reach detectable levels in some individuals. Their presence typically persists for months to years, depending on immune response.
Can this test tell me if I currently have COVID-19?
No, this test only detects antibodies from a past infection. To determine if you have an active COVID-19 infection, you would need a different test, such as a PCR or antigen test.
What does a positive result mean?
A positive result indicates that your immune system has likely encountered the virus in the past, meaning you may have had COVID-19. However, it does not guarantee immunity against future infection, as immunity can vary among individuals.
  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