WEDNESDAY, Sept. 19, 2022 (HealthDay News) — During the period of omicron emergence, the performance of COVID-19 rapid antigen tests with nasal self-sampling declined, according to a study published online Sept. 14 in The BMJ.

Ewoud Schuit, Ph.D., from Utrecht University in the Netherlands, and colleagues conducted a diagnostic test accuracy study at three public health service COVID-19 test sites from Dec. 21, 2021, to Feb. 10, 2022. Participants had a swab sample taken for reverse transcription polymerase chain reaction and received a rapid antigen test to perform unsupervised using nasal self-sampling (during the emergence of omicron and when omicron accounted for >90 percent of infections) or with combined oropharyngeal and nasal self-sampling (when omicron accounted for >99 percent of infections; phases 1 and 2, respectively). Flowflex (phase 1 only), MPBio, and Clinitest were evaluated.

The researchers found that the overall sensitivities with nasal self-sampling were 79.0, 69.9, and 70.2 percent for Flowflex, MPBio, and Clinitest, respectively. Compared with those tested for other reasons, the sensitivities were substantially higher in confirmatory testers (93.6, 83.6, and 85.7 percent versus 52.4, 51.5, and 49.5 percent, respectively). When transitioning from omicron accounting for 29 percent of infections to >95 percent of infections, the sensitivities decreased from 87.0 to 80.9 percent, 80.0 to 73.0 percent, and 83.1 to 70.3 percent (statistically significant), respectively. With combined oropharyngeal and nasal self-sampling, sensitivities were 83.0 and 77.3 percent for MPBio and Clinitest, respectively; sensitivities were slightly higher in confirmatory testers (87.4 and 86.1 percent, respectively) and substantially higher in those testing for other reasons (69.3 and 59.9 percent, respectively).

“The performance of rapid antigen tests can be improved by adding oropharyngeal to nasal self-sampling,” the authors write.

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