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Antigen and Molecular Tests for COVID-19

The diagnostic testing field for COVID-19 is rapidly evolving and improving in quality every day, with many tests focused on diagnosing patients with active viral infections. Diagnostics able to detect current, active infections are typically molecular-based diagnostics, which inform researchers of the presence of the pathogen, either by identifying its genetic material or identifying unique markers of the pathogen itself. The viral genomic material for SARS-CoV-2 is ribonucleic acid (RNA), which remains in the body only while the virus is still replicating. There are also rapid antigen tests in development that act by detecting specific viral proteins (antigens) that are found on the surface of the virus particle, which are also shed in patient tissues. These antigens can be detected in nasal or nasopharyngeal swabs. Antigen tests do not amplify the viral material, but detect only that which is present in the patient sample.

Molecular diagnostics usually require samples from the patient that are likely to contain virus, such as nasopharyngeal swabs or sputum samples. Some pathogens may also be detected in feces, urine, or blood. For respiratory diseases like COVID-19, nasopharyngeal swabs have been considered to be the most reliable, as they sample an area of the respiratory tract where the virus appears to first infect an individual. This site is relatively easily accessed, compared to the final site of viral infection: the lower respiratory tract. Consequently, the nasopharyngeal tract likely has (1) active virus replication and (2) sufficient amounts of virus to be detected in kits. Many tests now available or in development can use saliva or nasal swabs that facilitate easier sampling procedures for healthcare providers and patients.

If you are looking for information on serology (antibody) tests, please visit our serology tracker or visit our recent report outlining the needs of a national serology strategy.

 

Disclaimer

This website is updated twice weekly and includes only tests with EUA status, either from commercial manufacturers or laboratory-developed tests. In the Assays in Development section, novel methodologies for direct detection of SARS-CoV-2 are described. While the described methodologies are appropriately cited, exact specifications of these tests will not be directly incorporated into the tracker tables until they receive FDA EUA status. This website is not intended to be used as a reference for funding or grant proposals. Non-inclusion in this list should not be interpreted as a judgment on the validity or legitimacy of tests.

If you are a manufacturer or research institution that has an EUA-approved molecular test that is not yet listed and you would like to contact us, please submit your information here. Submission of this form does not guarantee inclusion on the website, but it will allow us to verify your test's information so that we can accurately describe the test if it is included.

 

Note on sensitivity and specificity data

Where available, we list the manufacturer-reported sensitivity and specificity data. A highly sensitive test should capture all true positive results. A highly specific test should rule out all true negative results. These measures are not independently validated by the Johns Hopkins Center for Health Security. If sensitivity or specificity is not listed, it was not available from the manufacturer at the time of posting. When available, the number of samples used for sensitivity/specificity definitions are listed in the product description.

It should also be noted that the terms “sensitivity” and “specificity” may not appear in the manufacturers’ information sheets, but rather these values are often reported as “positive percent agreement” and “negative percent agreement.“ Sensitivity may also be measured by calculating the limit of detection (LOD), which is the lowest detectable number of virus copies in a sample at which the test will return a positive result at least 95% of the time. Essentially, a lower limit of detection indicates a more sensitive test, with fewer viral copies per sample necessary to elicit a positive test result. The FDA recommends that manufacturers use these terms to indicate that a nonreference standard was used when evaluating the test.