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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 vaccination status."]

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

Key facts at a glance

LOINC
13160-7
Short code
Deprecated S pneum19 Ab sp2 Ser-aCnc
Synonyms
Deprecated S pneum19 Ab sp2 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’ve had symptoms of COVID-19, were exposed to the virus, or if you’re part of a study or screening program. It can also be used to confirm previous infection in certain settings, such as before returning to work or travel.

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 will be sent to a lab for analysis.

What the Test Results Mean

Positive results indicate the presence of antibodies against the virus’s nucleocapsid protein, suggesting past infection. Negative results mean no detectable antibodies were found at this time. Results do not confirm current infection and may not be accurate if tested too soon after exposure.

Common Reasons for Testing

This test is often used in: • Post-exposure screening (e.g., after close contact with someone with COVID-19), • Vaccination status verification (though antibodies may decline over time), • Research or public health surveillance programs.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Limitations and Considerations

Short name

SARS-CoV-2 Nucleocapsid Antibody (IgG)

Frequently asked questions

Why might my antibody levels be low or absent?
Antibody levels can vary widely depending on when you were infected, the severity of illness, and your immune response. Some people naturally produce fewer antibodies, and levels may drop over time after infection. Antibodies may also not develop if you were infected early in the illness or had mild symptoms.
Does this test replace a COVID-19 PCR or antigen test?
No. Antibody tests detect past exposure, while PCR or antigen tests identify active infection. If you’re concerned about current illness, a PCR test is more reliable for diagnosing active COVID-19.
Can I get COVID-19 again if my antibody test is negative?
Yes. Antibody tests do not guarantee immunity. While antibodies may help your immune system recognize the virus, they do not prevent reinfection. Vaccination remains the best way to reduce the risk of severe illness.
  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