The FLARE Four
- Reverse-transcriptase polymerase chain reaction (RT-PCR) is currently the method of choice for detecting SARS-CoV-2, the virus responsible for the COVID-19 pandemic
- Direct fluorescent antibody labeling is under development for testing for SARS-CoV-2; it would be much faster but at this time the sensitivity is inadequate
- Serological tests promise to supplement RT-PCR-based testing strategies
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Reverse-transcriptase polymerase chain reaction (RT-PCR) is currently the method of choice to diagnose novel coronavirus, SARS-CoV-2. Physicians Laura Brenner, MD, and Vladimir Vinarsky, MD, of the Division of Pulmonary and Critical Care in the Department of Medicine at Massachusetts General Hospital, explain why—and review potential forthcoming alternatives—in a fast literature update posted on April 6, 2020.
RT-PCR detects genetic sequences unique to an RNA virus such as SARS-CoV-2. It can make use of a small amount of viral RNA, making it highly sensitive. It's also very specific because the nucleic acid primers are designed to bind to the genetic sequences in SARS-CoV-2 and not to any part of other known viral or human genomes.
Direct Fluorescent Antibody (DFA) Labeling
DFA labeling detects antigens unique to a virus. An antibody is raised against the antigen and conjugated to a reporter molecule (e.g., a fluorescent molecule). When the conjugated antibody binds its target antigen, the virus becomes detectable by a method specific to the reporter (e.g., fluorescence microscopy).
DFA-based tests are typically much faster than RT-PCR and are under development for detecting SARS-CoV-2. Presently, their sensitivity is inadequate; during the pandemic, patients who test negative must be truly negative.
Immunoassays show promise to be used in combination with PCR to answer the vital clinical question: Does this patient have SARS-CoV-2?
Testing for antibodies against a virus's antigens can be used to determine the efficacy of vaccines, identify donors for convalescent plasma, confirm past infections and tell epidemiologists the number of people exposed. Serologic testing may also prove useful clinically where direct viral testing is indeterminate.
View all COVID-19 updates
Learn more about research at the Division of Pulmonary & Critical Care at Mass General