Rapid COVID-19 Antigen Tests Less Effective at Detecting SARS-CoV-2 in People with Low Virus Levels, Finds Study

Antigen-based assays detect specific surface proteins, or antigens, on SARS-CoV-2 particles, and are easy to use and inexpensive to produce. The researchers used five commercially available rapid antigen assays on samples from 1,754 people who had already tested positive for the SARS-CoV-2 virus with the standard PCR test, which is highly sensitive but slow.

The team found that the detection limits of the five commercially available RDTs differed considerably, impacting the translation into the detection of infectious cases. The two most sensitive tests detected the SARS-CoV-2 virus more than 97% of the time, whereas the least sensitive test detected the novel coronavirus in about 75% of the cases. All the samples came from people with COVID-19 symptoms, who tend to have high levels of the SARS-CoV-2 virus. Based on their findings, the researchers have cautioned that rapid antigen tests may be less effective at picking up the presence of the SARS-CoV-2 virus in people with low levels of the virus. The researchers have recommended careful fit-for-purpose testing before implementation of antigen RDTs in routine testing algorithms as part of the COVID-19 response.

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Erasmus University Medical Center