Summary of Recent Changes Revisions were made on December 5, 2020 including: The word “rapid” has been deleted because FDA has authorized laboratory-based antigen tests New section on processing of antigen tests, reflecting what has been learned on how to minimize the risk of false results Revised section on evaluating the results of antigen tests, introducing a new testing algorithm, and reflecting what has been learned about the performance of antigen tests and the need to implement confirmatory testing Note: Antigen tests can be used in a variety of testing strategies to respond to the coronavirus disease 2019 (COVID-19) pandemic This interim guidance is intended for clinicians who order antigen tests, receive antigen test results, and perform point-of-care testing, as well as for laboratory professionals who perform antigen testing in a laboratory setting or at the point of care and report those results The purpose of this interim technical guidance is to support effective clinical use of antigen tests for different testing situations This guidance applies to all clinical uses of antigen tests and is not specific to any particular age group or setting This guidance supplements and is consistent with CDC’s Overview of Testing for SARS-CoV-2 guidance CDC has also provided a Summary of considerations for using antigen tests in nursing homes Antigen Testing for SARS-CoV-2 General Guidance Antigen tests are commonly used in the diagnosis of respiratory pathogens, including influenza viruses and respiratory syncytial virus The U S Food and Drug Administration (FDA) has granted emergency use authorization (EUA) for antigen tests that can identify SARS-CoV-2 See FDA’s list of In Vitro Diagnostics EUAsexternal icon Antigen tests are immunoassays that detect the presence of a specific viral antigen, which implies current viral infection Antigen tests are currently authorized to be performed on nasopharyngeal or nasal swab specimens placed directly into the assay’s extraction buffer or reagent The currently authorized antigen tests are not restricted to use on persons of a certain age See Table 1 for additional information about antigen tests Antigen tests are relatively inexpensive, and most can be used at the point of care Most of the currently authorized tests return results in approximately 15 minutes Antigen tests for SARS-CoV-2 are generally less sensitive than real-time reverse transcription polymerase chain reaction (RT-PCR) and other nucleic acid amplification tests (NAATs) for detecting the presence of viral nucleic acid However, RT-PCR can detect levels of viral nucleic acid that cannot be cultured, suggesting that the presence of viral nucleic acid does not always indicate contagiousness Proper interpretation of both antigen test results and confirmatory testing when indicated is important for accurate clinical management of patients with suspected COVID-19, or for identification of infected persons when used for screening The clinical performance of antigen diagnostic tests largely depends on the circumstances in which they are used Both antigen tests and NAATs perform best when the person is tested when viral load is generally highest They also may be informative in diagnostic testing situations in which the person has a known exposure to a person with COVID-19 There are increasing amounts of dataexternal icon to help guide the use of antigen tests as screening tests on asymptomatic persons to detect or exclude COVID-19, or to determine whether a person who previously was diagnosed with COVID-19 remains infectious See FDA’s Recommendations for healthcare providers using SARS-CoV-2 diagnostic tests for screening asymptomatic individuals for COVID-19external icon Also see information from the Centers for Medicare & Medicaid Services (CMS) on Enforcement discretion for the use of SARS-CoV-2 point-of-care testing on asymptomatic individuals pdf iconexternal icon Antigen tests can be used for screening testing in high-risk congregate settings in which repeat testing could quickly identify persons with a SARS-CoV-2 infection to inform infection prevention and control measures, thus preventing transmission In this case, and especially in settings where a rapid test turnaround time is required, there is value in providing immediate results with antigen tests, even though they may have lower sensitivity than NAATs Clinicians and public health practitioners should understand test performance characteristics to recognize potentially false negative or false positive test results and to guide additional confirmatory testing and patient management Laboratory and testing professionals who perform antigen tests should understand the factors that affect the accuracy of antigen testing, as described in this guidance Clinicians, laboratory and testing professionals, and public health practitioners should also understand the differences among diagnostic, screening, and surveillance testing See CDC’s Overview of Testing for SARS-CoV-2, and Testing Strategies for SARS-CoV-2 Also see FDA’s FAQs on Testing for SARS-CoV-2external icon
Interim Guidance for Antigen Testing for SARS-CoV-2