Swab Testing (testing for current infection)
A nurse collects a nasal swab to look for active infection with the novel coronavirus (SARS-CoV-2, the virus that causes COVID-19).
The results will be one of the following:
- Detected, meaning most likely you DO currently have active COVID-19
- Not detected, meaning most likely you DO NOT currently have active COVID-19
- Inconclusive, meaning the test was unable to determine if you have active COVID-19
- Invalid, meaning there was something wrong with the nasal swab sample, so testing for active COVID-19 was not possible
- Test not performed, the COVID-19 test was not done. This could be because no sample was collected, or for another reason
If it is most likely that you HAVE a current active COVID-19 infection, you can give the virus to others. We recommend that you stay home and follow all CDC guidance (https://www.cdc.gov/coronavirus) on steps to take if you are sick. If you are a healthcare or critical infrastructure worker, notify your work of your test result.
If it is most likely that you DO NOT HAVE a current active COVID-19 infection, if you develop symptoms, you should monitor symptoms and seek medical advice about staying home and if you need to get tested again. If you don’t have symptoms, you should get tested again only if your medical provider and/or workplace tells you to.
Antibody Testing (testing for past infection with the virus)
The nurse also collects a blood sample to test for antibodies, to look for evidence of past infection with the novel coronavirus. Antibodies are proteins that are produced by the immune system in response to a specific infection. Your blood was tested for two antibodies: IgG and IgM.
Both IgG and IgM begin to develop 7 to 10 days after symptoms begin. IgM usually appears first, and then disappears from the blood relatively quickly. IgG appears a little bit later, and remains in the blood for several months.
The results will be one of the following:
- Both IgG and IgM are positive, meaning you most likely have active COVID-19, or have had it in the recent past
- Both IgG and IgM are negative, meaning you most likely HAVE NOT had COVID-19 in the past
- IgG is positive and IgM is negative, meaning you most likely had COVID-19 several weeks or longer in the past
- IgG is negative and IgM is positive, meaning you most likely have active COVID-19, or have had it in the recent past
If it is most likely that you HAD a COVID-19 infection, you may be protected from re-infection (have immunity), but this cannot be said with certainty. Scientists are conducting studies now to provide more information.
If it is most likely that you DID NOT HAVE a COVID-19 infection, you could still get COVID-19.
No test is ever perfect. All tests occasionally result in false positive results (the test result should be negative because you DO NOT have COVID-19 but comes back positive) or false negative results (the test result should be positive because you DO have COVID-19, but comes back negative). Sometimes the results are not definitive (the result is unclear, and you don’t know if it is positive or negative). For this and other reasons, results should always be reviewed by a healthcare professional.
Note that the antibody tests are not yet approved or cleared by the United States Food and Drug Administration (FDA). When there are no FDA-approved or cleared tests available, and other criteria are met, FDA can make tests available under an emergency access mechanism called an Emergency Use Authorization (EUA). The EUA for this test is supported by the Secretary of Health and Human Service’s (HHS’s) declaration that circumstances exist to justify the emergency use of in vitro diagnostics for the detection and/or diagnosis of the virus that causes COVID-19. This EUA will remain in effect (meaning this test can be used) for the duration of the COVID-19 declaration justifying emergency of IVDs, unless it is terminated or revoked by FDA (after which the test may no longer be used).
