Widespread testing and tracing are crucial to managing the spread of COVID-19, but there are several different kinds of tests that each have a specific use.
We spoke to David Louis, MD, chief of Pathology at Massachusetts General Hospital, Anthony John Iafrate, MD, director of the Center for Integrated Diagnostics, and Eric Rosenberg, MD, director of the Clinical Microbiology Laboratory, to get the scoop on each type of test and why they are important for patients and clinicians.
If you’ve been thinking about getting tested for COVID-19, check out facts below to learn about which one may be right for you.
PCR (Polymerase Chain Reaction) Test
Method of analysis:
The test uses an amplification process to detect the presence of viral RNA in the airway of the nose and throat (collected via nasal swab).
When it is used:
When a patient is being evaluated for an active SARS-CoV-2 infection. The test is most accurate when administered within the first week after symptoms begin.
Why it is important:
It provides confirmation of a SARS-CoV-2 infection, which allows clinically useful guidance for the patient and health officials
Limitations:
The PCR test provides evidence of active viral infection in the respiratory tract. Occasionally, this test may need to be performed twice to definitively rule out SARS-CoV-2 infection. It may come back negative for individuals who are later in their disease course and does not provide evidence of more distant past exposure.
Serology Tests
ELISA (Enzyme-Linked Immunosorbent Assay) Test
Method of analysis:
Examines blood for SARS-CoV-2-specific antibodies.
When it is used:
To see if an individual has developed antibodies in response to exposure to the SARS-CoV-2 virus.
Why it is important:
The ELISA test not only indicates the presence of antibodies, but can provide details on the levels of each different type of antibody – this creates a more complete picture of the body’s overall immune response.
Limitations:
Because it takes the body time to develop antibodies to a virus, a serology test may come back negative during the early days of infection even if the virus is present.
POC (Point of Care) Test
Method of analysis:
Examines blood for SARS-CoV-2-specific antibodies.
When it is used:
To see if an individual has developed antibodies in response to exposure to the SARS-CoV-2 virus. The POC test only indicates the presence or absence of antibodies, not the relative levels of each.
Why it is important:
POC tests are portable, can be performed in a variety of settings (workplace, urgent care clinics, etc.) and provide rapid results.
Limitations:
Because it takes the body time to develop antibodies to a virus, a serology test may come back negative during the early days of infection even if the virus is present. Since a POC test can only confirm the presence (or absence) of antibodies, it may not provide a full picture of the body’s immune response.
COVID-19 Research at Mass General
Researchers and clinicians at Massachusetts General Hospital Research Institute are mobilizing to develop new strategies to diagnose, treat and prevent COVID-19. Learn more.
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