FAQs on Testing for COVID-19 / SARS-CoV-2 Antigen Testing Kits
Q: Are antigen tests for COVID-19 accurate?
A: Campbell says, is that if an antigen test comes back positive right now, it is most likely accurate. “People who have a positive antigen test right now are almost certainly infectious and contagious. People who are antigen negative at the very worst are less contagious.
Q: How do COVID- 19 rapid antigen tests work?
A: Rapid antigen tests, which are less sensitive than P.C.R. tests, are designed to detect proteins on the surface of the virus. If genetic mutations alter these proteins, it could affect the tests’ ability to detect the virus. So each time a new variant emerges, researchers need to re-evaluate the tests.
Q: When should I take a COVID-19 rapid antigen test?
A: Contrary to what some still think is best, a rapid antigen test (or rapid lateral flow test) is what you should be taking after you have had Covid-19 for several days and want to confirm you’re probably no longer infectious to other people.
Q: Which COVID-19 tests are more accurate PCR or antigen tests?
A: PCR tests are more accurate than antigen tests. “PCR tests are the gold standard for detecting SARS-CoV-2,” says Dr. Broadhurst. “It is the most accurate testing modality that we have.
Q: What does a positive COVID-19 antigen test result mean?
A: Positive test results using a viral test (NAAT or antigen) in persons with signs or symptoms consistent with COVID-19 indicate that the person has COVID-19, independent of vaccination status of the person.
Q: How to verify if tests are authorized for use in US?
Q: What is a rapid COVID-19 antigen test?
A: A rapid COVID-19 test, also called an antigen test, detects proteins from the virus which causes COVID-19. This type of test is considered most accurate in those individuals who are experiencing symptoms of COVID-19. Rapid tests allow public health to detect disease sooner, decrease spread faster and start contact tracing earlier.
Q: What should I do if my at-home rapid test is positive?
A: If you have a positive test result, it is very likely that you have COVID-19. Talk to your health care provider and any possible close contacts. Regardless of vaccination status, everyone who tests positive should isolate.
Q: Are at-home COVID-19 rapid antigen tests accurate?
A: Yes. “At-home antigen tests are quite accurate, especially if you have symptoms,” Hafer says. Still, they have some limitations. Antigen tests are more likely to return a false negative if you’re infected but you don’t yet have symptoms.
Q: When is the best time to test for COVID-19 following an exposure?
A: The optimal time to test for COVID-19 following exposure is uncertain; five to seven days following exposure is recommended based on the average incubation period.
Q: What advice should be given to patients with known or presumed COVID-19 managed at home?
A: For most patients with COVID-19 who are managed at home, we advise the following:
- Supportive care with antipyretics/analgesics (eg, acetaminophen) and hydration
- Close contact with their health care provider
- Monitoring for clinical worsening, particularly the development of new or worsening dyspnea, which should prompt clinical evaluation and possible hospitalization
- Separation from other household members, including pets (eg, staying in a separate room when possible and wearing a mask when in the same room)
- Frequent hand washing for all family members
- Frequent disinfection of commonly touched surfaces
Q: What is the difference between surveillance, screening, and diagnostic testing for COVID-19 testing?
A: Surveillance for COVID-19 includes ongoing systematic activities, including collection, analysis, and interpretation of health-related data, essential to planning, implementing, and evaluating public health practice. It is generally used to monitor for an occurrence, such as an infectious disease outbreak, in a population or community, or to characterize the occurrence once detected, such as looking at the incidence and prevalence of the occurrence.
Screening for COVID-19 is looking for an occurrence at the individual level even if there is no individual reason to suspect infection such as a known exposure. This includes a broad screening of asymptomatic individuals without known exposure with the intent of making individual decisions based on the test results. Screening tests are intended to identify infected individuals prior to the development of symptoms or those infected individuals without signs or symptoms who may be contagious so that measures can be taken to prevent those individuals from infecting others.
Diagnostic testing for COVID-19 is also looking for an occurrence at the individual level but is performed when there is a particular reason to suspect that an individual may be infected. Diagnostic tests are intended to diagnose an infection in patients suspected of COVID-19 by their healthcare provider such as in symptomatic individuals, individuals who have had a recent exposure, individuals who are in a high-risk group such as healthcare providers with known exposure, or testing to determine the resolution of infection. Diagnostic tests may also be appropriate in areas of high community spread, at the discretion of the ordering healthcare provider. FDA regulates diagnostic tests as in vitro diagnostic devices and has provided recommendations and information regarding EUA requests for COVID-19 diagnostic tests in the Policy for Coronavirus Disease-2019 Tests and the EUA templates referenced in that Policy.
Q: Are antibody, or serology, tests used to diagnose SARS-CoV-2 infection?
A: The terms “serological” or “antibody” tests are generally used to refer to tests that detect antibodies to the SARS-CoV-2 virus. Because the antibodies are part of the body’s immune response to exposure and not the virus itself, such COVID-19 testing cannot be used for the diagnosis of infection. Based on the underlying scientific principles of antibody tests, we do not expect that an antibody test can be shown to definitively diagnose or exclude COVID-19 infection. SARS-CoV-2 antibody tests are intended for use as an aid in identifying individuals with an adaptive immune response to SARS-CoV-2, indicating recent or prior infection, by detecting antibodies to SARS-CoV-2 in human blood specimens.
Q: Does my facility need a CLIA certificate if we are performing SARS-CoV-2 surveillance testing using a pooled sampling procedure with non-patient-specific reporting?
A: During this COVID-19 Public Health Emergency, facilities performing SARS-CoV-2 surveillance testing using a pooled sampling procedure to report non-patient-specific SARS-CoV-2 cohort results will not require CLIA certification. This testing is not considered by CMS to be diagnostic of SARS-CoV-2 infection, and participants should not rely on information received from this type of testing for decision-making purposes.
Q: What is the difference between Molecular and Antibody tests?
A: Comparison of COVID-19 Molecular and Antibody Tests
A: People who receive positive results on an antibody test but don’t have symptoms of COVID-19 or have not been around someone who may have COVID-19 are not likely to have a current infection. They can continue with normal activities, including work, but still take steps to protect themselves and others. People who receive positive results on an antibody test and who are currently or recently sick or have been around someone with COVID-19 should follow CDC recommendations on caring for themselves and protecting others, and when they can be around other people again.