COVID-19 Testing: PCR, NAAT and Antigen Tests
COVID-19 viral tests look for current SARS-CoV-2 infection. NAATs, including PCR, are generally more sensitive; rapid antigen tests are faster but may miss infection, especially when viral levels are lower.
At a glance
Key points
- Main test types
- NAAT/PCR · antigen
- Most sensitive
- NAAT / PCR
- Rapid result
- Antigen · often 15–30 min
- Negative antigen
- May need repeat testing
- Positive result
- Virus detected / recent infection
- Recent infection
- NAAT can stay positive up to 90 days
What a COVID-19 test answers
Viral tests are designed to identify current infection. A test result is most useful when interpreted with timing, symptoms, recent exposure and recent infection history. Testing can also affect treatment decisions because antivirals for people at higher risk work best when started early.
Antibody tests answer a different question — whether the immune system has responded to prior infection or vaccination — and are not the standard way to diagnose a current infection.
Comparison
PCR / NAAT versus rapid antigen testing
Both can be useful, but their strengths differ.
| Feature | NAAT / PCR | Antigen |
|---|---|---|
| What it detects | Viral genetic material | Viral proteins |
| Sensitivity | Higher; CDC describes NAATs as the gold standard for diagnosis | Lower, especially when symptoms are absent or viral levels are lower |
| Speed | Often laboratory-based; some point-of-care tests are faster | Usually about 15–30 minutes |
| Negative result | A single NAAT can be used for confirmation in many situations | A single negative does not rule out infection; repeat testing may be recommended |
| After a recent infection | May remain positive for up to 90 days | Often preferred by CDC when evaluating possible reinfection during that period |
Evidence snapshot
How to interpret common results
A test result is a piece of evidence, not a complete clinical assessment.
A positive viral test means SARS-CoV-2 was detected
Follow current local guidance on reducing spread, monitor symptoms and seek prompt treatment advice if you have risk factors for severe disease.
A negative antigen test can be too early
If symptoms or exposure make infection plausible, repeat testing according to the test instructions and local guidance rather than assuming one negative rapid test excludes COVID-19.
A new positive result can be hard to interpret within 90 days
NAAT tests can remain positive after recovery. Reinfection can also occur, so test choice and symptom timing matter.
Sources
This page separates current clinical or public-health guidance from historical pandemic material. Recommendations can vary by country and may change as evidence evolves.
- 1. CDC. Testing for COVID-19. Source ↗
- 2. CDC. About reinfection. Source ↗
- 3. WHO. Coronavirus disease (COVID-19) fact sheet. Source ↗
This article is based on trusted medical sources and is awaiting clinician review. It is not a substitute for personalized medical advice.