Coronavirus rapid tests may be less effective for new variants

May 12, 2022 – Rapid antigen tests for diagnosing COVID-19 may be less effective for new coronavirus variants, particularly the delta variant, according to a joint study by researchers at Harvard T.H. Chan School of Public Health and Beth Israel Deaconess Medical Center.

Co-authors of the study, published April 20, 2022 in the Journal of Clinical Microbiology, included Phyllis Kanki, Mary Woodard Lasker Professor of Health Sciences, Sydney Stanley, Donald Hamel, and Ian Wolf.

Coronavirus variants have emerged throughout the pandemic, including the highly transmissible and mutated omicron variant that appeared in late 2021. Because rapid antigen tests were developed based on an early version of the virus, the researchers studied whether the tests are less effective in detecting the variants.

The researchers evaluated four common rapid antigen tests, including three designed to be used at home. While all of the tests could effectively detect the omicron variant, three of them were less effective in detecting the delta variant.

“Generally, these rapid antigen tests will be able to detect the most infectious individuals—those that would transmit the virus—which is the public health goal,” said Kanki. “Our results indicate that as new variants emerge, we need to be vigilant in reevaluating the performance of our laboratory tests.”

Read the Journal of Clinical Microbiology study: Limit of Detection for Rapid Antigen Testing of the SARS-CoV-2 Omicron and Delta Variants of Concern Using Live-Virus Culture