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Antigen test for SARS-CoV-2 nucleocapsid protein (rapid immunoassay, nasal swab specimen)

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

This test detects the presence of SARS-CoV-2, the virus responsible for COVID-19, by identifying specific proteins (nucleocapsid) found in the virus. It is used to help confirm infection, especially in individuals who may have symptoms or exposure risk.

Quick summary

["A rapid test to check for active COVID-19 infection by detecting viral proteins in your nose."]

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

Key facts at a glance

LOINC
112295-1
Short code
Flu A+B & RSV+SARS-CoV-2 Ag Pnl Nose IA.rapid
Synonyms
Flu A+B & RSV+SARS-CoV-2 Ag Pnl Nose IA.rapid
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-rapid
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

How the Test Works

The test uses a nasal swab to collect a sample of your upper respiratory tract. The swab is then analyzed in a rapid immunoassay that detects the nucleocapsid protein of SARS-CoV-2. If the virus is present, the test may show a positive result, indicating possible infection.

When You Might Need This Test

Your healthcare provider may recommend this test if you have symptoms like fever, cough, or shortness of breath, or if you’ve been exposed to someone with COVID-19. It can also be used for screening in certain settings, such as before gatherings or travel.

Limitations and Considerations

This test is designed to detect active infection and may not be as sensitive as PCR tests in all cases. False negatives can occur if the test is taken too early after exposure or if symptoms are mild. Results should always be interpreted by a healthcare professional.

What to Expect Before the Test

No special preparation is needed. You may blow your nose first to clear nasal passages, but avoid using nasal sprays or decongestants before testing, as they could affect results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Role in COVID-19 Diagnosis and Management

Short name

SARS-CoV-2 Nucleocapsid Antigen Test

Frequently asked questions

Why is this test important?
This test helps quickly identify active COVID-19 infections, allowing for early isolation, treatment initiation, and contact tracing. It is particularly useful for rapid screening in high-risk or high-exposure settings where PCR testing may not be immediately available.
Can this test replace PCR testing?
No, this test is not a substitute for PCR testing. PCR tests are generally more sensitive and can detect earlier in the infection course, while antigen tests are faster and more convenient but may miss some cases, especially in the early or late stages of infection.
What if my test result is positive?
If your test is positive, you should isolate yourself from others to prevent spreading the virus. Follow your healthcare provider’s guidance for next steps, which may include further testing, treatment, or monitoring. Always confirm results with additional testing if possible.
  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