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 September 14 in The BMJ.

Ewoud Schuit, PhD, from Utrecht University in the Netherlands, and colleagues conducted a diagnostic test accuracy study at 3 public health service COVID-19 test sites from December 21, 2021, to February 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% of infections) or with combined oropharyngeal and nasal self-sampling (when omicron accounted for >99% 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% 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% vs 52.4, 51.5, and 49.5%, respectively). When transitioning from omicron accounting for 29% of infections to greater than 95% of infections, the sensitivities decreased from 87.0 to 80.9%, 80.0 to 73.0%, and 83.1 to 70.3% (statistically significant), respectively. With combined oropharyngeal and nasal self-sampling, sensitivities were 83.0 and 77.3% for MPBio and Clinitest, respectively; sensitivities were slightly higher in confirmatory testers (87.4 and 86.1%, respectively) and substantially higher in those testing for other reasons (69.3 and 59.9%, respectively).

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

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