The most noticeable difference between antigen screening and PCR tests is the time it takes to get results. The rapid antigen screenings that are being conducted in North Dakota right now are likely BinaxNOW tests. These screenings are performed via a nasal swab of each nostril inserted midway into the nasal cavity, less invasive than the PCR nasal swab. The sample is placed onto a test card where results are interpreted visually based on the presence of pink/purple colored lines. Results are available in 15 minutes. Cost is also a significant difference between the two testing types. Antigen screening cost about $5.50 per kit while PCR tests are about $100 per test.
Antigen screening and PCR tests are both diagnostic tools that show if an individual has an active coronavirus infection. Both tools are what have been primarily used for larger testing events in our region. PCR tests detect a virus’s genetic material, while antigen screening detects specific proteins from the virus. A third type of testing, using antibodies, can determine if you’ve been infected by COVID-19 in the past. More information about the types of testing is available at https://www.fda.gov/consumers/consumer-updates/coronavirus-disease-2019-testing-basics#:~:text=Currently%20there%20are%20two%20types,specific%20proteins%20from%20the%20virus.
The samples gathered from a PCR test are collected from a swab from the back of the throat or from the nasal cavity. These collected samples are sent to a lab to be analyzed. Results can be determined in hours, to days, depending on lab capacity.
Presently, North Dakota is incorporating more rapid antigen screening into its overall testing plan. While PCR will likely not disappear completely, the flexibility of antigen screening application and speed of antigen results, makes its use appealing. Ideally, antigen screening should be used on consistent, reoccurring intervals to help ensure reliable results.
Rapid tests are not as sensitive as PCR tests and do have a higher false-negative rate, meaning you may test negative, but still have the virus. Antigen screening performs best when the person is symptomatic and is screened in the early stages of infection with SARS-CoV-2 when viral load is generally highest (https://www.health.nd.gov/sites/www/files/documents/Webpage%20Updates/Rapid_Antigen_Testing_FAQ.pdf).
A negative test result for this test means that antigens from SARS-CoV-2 were not detected in your sample so you may not have COVID-19. However, a negative result does not rule out COVID-19 and should not be used as a pass to stop practicing social distancing and other COVID-19 prevention measures. A negative COIVD-19 test means you likely did not have COVID-19 at the time you were tested. You could have been tested too early to be detected or could be exposed to COVID-19 after the test and get infected then (https://www.health.nd.gov/sites/www/files/documents/Files/MSS/coronavirus/Guidance/Fact_Sheet_Rapid_Antigen_Testing.pdf).
More information about antigen tests is available at https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.html.