by Kristina Fiore, Director of Enterprise & Investigative Reporting, MedPage Today September 14, 2022

The performance of certain at-home rapid antigen tests declined during Omicron, Dutch researchers found.

From December 2021 to February 2022, sensitivities for three commonly used tests in the Netherlands dropped, though only the decline with Clinitest was statistically significant:

Adding an oropharyngeal swab to the standard nasal swab boosted the sensitivity of the tests, Karel Moons, PhD, of University Medical Center Utrecht, and colleagues reported in The BMJ.

Still, in an accompanying editorial, Timothy Feeney, PhD, and Charles Poole, ScD, both of the University of North Carolina at Chapel Hill, wrote that no test "reached anywhere near the level of performance advertised by the manufacturers."

Data on the true sensitivity and specificity of at-home rapid antigen tests commonly used in the U.S. -- such as Abbott's BinaxNOW and Becton Dickinson's BD Veritor -- have been sparse.

Back in July, the FDA sent an updated MedWatch alert noting a diminished sensitivity with rapid antigen tests due to the Omicron variant, but did not provide the study results supporting the update.

An FDA spokesperson told MedPage Today at the time that "the information that is on the website is what is available at this time."

Also at that time, a spokesperson for the NIH's RADx program, which evaluates COVID diagnostics, told MedPage Today that data on test performance are "not published immediately," and referenced a medRxiv publication from this past March by the RADx team showing no difference in sensitivity with Delta versus Omicron for BinaxNOW, BD Veritor, or Quidel QuickVue.

The spokesperson said he did not, however, have any more recent data.

FDA lists at least 22 at-home rapid tests currently available on the U.S. market. While the agency does not note their sensitivity and specificity data, it does link to each test instructions for use (IFU), which include data that the companies used to garner FDA emergency use authorization.

The IFU for Abbott's BinaxNOW antigen self-test, for instance, states that the test identified 91.7% of positive specimens and 100% of negative specimens -- a far cry from the sensitivities revealed in The BMJ report.

For their study, Moons and colleagues studied 6,497 people ages 16 and up who had COVID-19 symptoms and were tested at three public health service test sites in the Netherlands from Dec. 21, 2021 to Feb. 10, 2022. All of them had a reference PCR test and were asked to complete at-home rapid antigen testing within 3 hours of their visit.

Initially, participants used only a nasal swab, but as the prevalence of Omicron increased, participants were asked to do both nasal and oropharyngeal sampling.

Although sensitivities declined with Omicron, the researchers found that doing both nasal and oral swabs raised sensitivity back up for MPBio (69.9% to 83%) and Clinitest (70.2% to 77.3%). Combined sampling was not done for Flowflex, they noted.

Overall specificities were above 92% and positive predictive values were above 94% for all three tests, according to the study.

Moons and colleagues said that only MPBio using a combined nasal and oropharyngeal swab met the World Health Organization's standards for rapid antigen tests at ≥80% sensitivity and ≥97% specificity among symptomatic people.

One possible reason for the lower sensitivity during Omicron could have to do with mutations in the nucleocapsid protein of the virus, which is what rapid antibody tests rely on to detect its presence, the researchers said.

The study was limited by its observational nature, but nonetheless, the researchers said they were "confident that combined oropharyngeal and nasal self-sampling is superior to nasal self-sampling only in the Omicron era."

Makers of rapid antigen tests "should consider extending their instructions for use to include combined oropharyngeal and nasal self-sampling," they wrote.

They also concluded that "positive predictive values were high throughout our study, and people with COVID-19 symptoms can therefore rely on a positive rapid antigen test result irrespective of SARS-CoV-2 variant dominance or method of self-sampling. Negative predictive values were much lower. Individuals with a negative self-test result should adhere to general preventive measures because a false negative result cannot be ruled out."

Editorialists Feeney and Poole also emphasized that a "single negative test result cannot be interpreted in a vacuum."

Kristina Fiore leads MedPage’s enterprise & investigative reporting team. She’s been a medical journalist for more than a decade and her work has been recognized by Barlett & Steele, AHCJ, SABEW, and others. Send story tips to k.fiore@medpagetoday.com. Follow

The study was funded by the Dutch Ministry of Health, Welfare, and Sport.

The authors disclosed no relevant financial conflicts of interest.

Source Reference: Schuit E, et al "Diagnostic accuracy of covid-19 rapid antigen tests with unsupervised self-sampling in people with symptoms in the omicron period: cross sectional study" BMJ 2022; DOI: 10.1136/bmj-2022-071215.

Source Reference: Feeney T, Poole C "Self-testing for covid-19" BMJ 2022; DOI: 10.1136/bmj.o2055.

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