COVID-19 and Influenza Rapid Antigen Tests
Definition
There are two basic test approaches:
| Antigen test | Molecular test (PCR/NAAT) | |
|---|---|---|
| What it detects | The virus's surface proteins | The virus's genetic material |
| Time | Within minutes | Laboratory: 1 to 3 days · Rapid PCR: minutes |
| Accuracy | Lower | Higher |
| Can it be done at home | Yes | Usually no |
Purpose
Rapid detection of COVID-19, influenza (flu), RSV and adenovirus infections. AdaGen's combined panels distinguish these pathogens, which cause similar symptoms, in a single sample.
Results
The most critical information is what a negative result means:
For COVID-19:
Antigen tests are not as reliable as PCR tests, especially if you have no symptoms.* If the antigen test is negative but symptoms persist, the physician may order a PCR. For home tests, *at least one more test after 48 hours should be performed.
For flu:
If the rapid antigen test is negative but you have flu symptoms, your test may have been done when there was only a small amount of virus in your body. Additional testing may be needed.
⏱Why timing matters:
Flu antivirals work best when started within 2 days of becoming ill. For this reason early testing can be important, especially in people at high risk of severe illness.
Sample types: Nasopharyngeal swab (from the nose to the upper throat), anterior nasal swab, nasal wash/aspirate. Conjunctival swab when avian influenza (H5) is suspected.
Risks and Limitations
A negative rapid test does not rule out the disease. The sensitivity of the test depends on the viral load; the likelihood of a false negative increases very early or very late in the illness.