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

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

This test detects antibodies to the SARS-CoV-2 nucleocapsid protein, which may help identify past infection with the virus responsible for COVID-19.

Quick summary

["This test helps determine if you’ve had prior exposure to COVID-19."]

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

Key facts at a glance

LOINC
94504-8
Short code
SARS-CoV-2 Ab Pnl SerPl IA
Synonyms
SARS-CoV-2 Ab Pnl SerPl IA
Category
chemistry
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 nucleocapsid protein is a structural component of the SARS-CoV-2 virus. After infection, your immune system produces antibodies against it. This test measures the presence of these antibodies in your blood, which can indicate past exposure to the virus.

Why It’s Done

Doctors may order this test to confirm a previous COVID-19 infection, especially if symptoms were mild or unclear. It can also be used in research or surveillance studies to track virus spread.

Sample Collection

A blood sample is drawn from a vein in your arm. You may feel a small pinch, but it usually doesn’t cause discomfort afterward.

When Results Might Be Positive

Results may be positive as early as 1–3 weeks after infection, depending on when your immune system responds. Antibody levels typically rise over time and can remain detectable for months or longer.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Anti-Nucleocapsid IgG/IgA/IgM

Frequently asked questions

When would I get this test?
Your doctor may recommend this test if you had mild COVID-19 symptoms, received a negative PCR test but suspect exposure, or are part of a study tracking antibody responses.
What does a positive result mean?
A positive result means your body has produced antibodies against the virus’s nucleocapsid protein, indicating past infection. It does not confirm immunity or rule out reinfection, as immunity varies by individual.
How long do antibodies stay in my system?
Antibodies can persist for months or years after infection, but their levels may decline over time. Some people develop stronger, longer-lasting immunity, while others may lose detectable antibodies.
  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