Coronavirus tests are making headlines, but confusion remains. Different tests detect different things and have different uses. We walk through the three main types of tests related to SARS-CoV-2, the virus that causes COVID-19: what each test detects, how it detects it and what the test can tell us about current and prior infection.
Think you need to get tested for COVID-19? Read the CDC’s guidance on who should get a test. Please use tests only as directed by your healthcare provider.
Also, read the FDA’s answers to frequently asked questions relating to the development and performance of tests for SARS-CoV-2.
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This test detects bits of the virus itself and can tell you if you’re currently infected. Swabs are used to collect samples from the mucus membranes in the nose and throat where the virus may be growing or have been coughed up from the lungs. There are two types of tests that detect SARS-CoV-2’s genetic material, or RNA: PCR tests and isothermal amplification, or IA, tests. Because RNA is made up of nucleic acids, both PCR and IA tests are also called nucleic acid amplification technology, or NAAT, tests. PCR tests are considered the gold-standard of NAAT testing.
These tests detect viral proteins, or antigens, in a sample taken using a nasal swab. This type of test can detect an active infection much faster than the PCR test and doesn’t need a specialized lab to run. However, it’s more likely to return an inaccurate result. Inaccurate results come in two types: Either the test wrongly suggests that someone who is infected with SARS-CoV-2 is virus-free (known as a false negative), or the test wrongly suggests that someone who is actually uninfected is carrying the virus (known as a false positive).
If you’ve gotten a blood test, antibody test, or serology test, you’ve been tested for an immune response to SARS-CoV-2. This type of test uses a blood sample to detect specific immune proteins known as antibodies. These are found in the serum, the clear liquid that remains when clotting proteins and cells have been removed from blood. Our bodies make antibodies in response to infections, including coronaviruses. The ELISA assay is the most common method used to detect these antibodies.
While we produce antibodies to coronavirus during infection, antibodies to viruses also linger long after the infection has passed, which makes serology tests poor indicators of active infection. Additionally, most serology tests are designed detect a type of antibody that arises later during an infection, making them better at showing prior exposure.
What these type of antibody tests cannot do is show whether someone is protected from reinfection by SARS-CoV-2. A different type of test, which measures how well a person’s antibodies block infection by the novel coronavirus, gets closer to showing whether they’re protected or not. (These tests are not yet available in clinical settings.) Scientists are currently studying the question of how well antibody levels — whether after infection or vaccination — correlate with protection against infection (or reinfection) by SARS-CoV-2.
And while the ELISA is a major type of serology test, it’s not the only one available. Several kinds of tests, including those that use technology similar to pregnancy tests, have hit the market become available, though not all give reliable results.
Located on Fred Hutch's South Lake Union campus in Seattle, the COVID-19 Clinical Research Center conducts Phase 1-3 clinical trials to find effective treatments for people who are positive for SARS-CoV-2.
Formed by the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, CoVPN conducts Phase 3 efficacy trials of COVID-19 vaccines and monoclonal antibodies to prevent COVID-19.
More than 30 U.S. cancer centers and organizations, including Fred Hutch and its clinical care partner Seattle Cancer Care Alliance, have come together to collect and disseminate data to better understand the scope and severity of COVID-19 in patients with cancer.
The Seattle Vaccine Trials Unit, part of Fred Hutch, is looking for people who are at risk for COVID-19 or have tested positive for the virus that causes COVID-19 to take part in a research study. Individuals are needed to help us learn more about how the virus affects the immune system.
Fred Hutch researchers are seeking healthy adults without current or past history of COVID-19 to take part in a research study about COVID-19 immunity. Volunteers will be paid to perform weekly home testing for COVID-19 and complete symptom questionnaires.