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Fluorescent Immunoassay for Anti-SARS-CoV-2 Nucleocapsid Antibodies (Serum)

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

This test detects antibodies produced in response to the SARS-CoV-2 virus, specifically targeting its nucleocapsid protein. It helps determine if your immune system has recognized and fought the virus, often used in COVID-19 testing.

Quick summary

["This test checks for past infection by measuring antibodies to a key viral protein."]

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

Key facts at a glance

LOINC
108007-6
Short code
FLUAV Ab Msmt Ser
Synonyms
FLUAV Ab Msmt Ser
Category
chemistry
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, recovered, or are in a setting where exposure risk is high. It can also be used to confirm previous infection in individuals who tested positive by antigen or PCR tests but are unsure about antibody development.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample from a vein, typically drawn in a clinic or lab. The serum portion of your blood is tested for antibodies using a fluorescent immunoassay method.

What the Test Results Mean

Positive results indicate the presence of antibodies against the nucleocapsid protein, suggesting your body has likely encountered SARS-CoV-2 before. Negative results mean no detectable antibodies were found at this time, which may indicate no prior infection or insufficient antibody production.

Common Reasons for Testing

This test is often used to assess immunity after recovery from COVID-19, evaluate exposure risk in high-risk populations, or confirm past infection in cases where symptoms were mild or testing was inconclusive.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Anti-Nucleocapsid Antibody Test (Serum)

Frequently asked questions

What does a positive result mean?
A positive result means your immune system has detected and produced antibodies against the SARS-CoV-2 nucleocapsid protein, suggesting you likely had a prior infection. However, this does not guarantee immunity from future infections.
Can I get this test if I’ve never had COVID-19?
If you’ve never had COVID-19, you may not have detectable antibodies. This test is most useful for individuals who suspect past exposure or have recovered from symptoms.
How long do I need to wait after infection to get accurate results?
Antibodies typically develop within 2–3 weeks after infection. Results may be less reliable if tested too soon after exposure or symptoms. Discuss timing with your healthcare provider for optimal interpretation.
  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