Study: At-home COVID-19 Tests Less Effective After Omicron Emergence

The performance of 3 commercially available COVID-19 home-testing kits worsened during the emergence of the omicron variant, according to a new prospective cross-sectional study published in the BMJ.

“Self-testing for SARS-CoV-2 may potentially lower the threshold for testing and would allow individuals to obtain a result quickly and at their own convenience, which, in turn, could support the early detection of infectious people and reduce community transmission,” wrote authors led by Ewoud Schuit, MSc, PhD, assistant professor at the University Medical Center Utrecht, Utrecht University, Netherlands. “Real-world evidence on the performance of unsupervised nasal and combined oropharyngeal and nasal self-sampling in the omicron variant period is needed to accurately inform end users and policymakers.”

Schuit and colleagues assessed the performance of rapid antigen tests with unsupervised nasal and combined oropharyngeal and nasal self-sampling during the omicron period. The tests were performed on 6497 people with COVID-19 symptoms aged ≥16 years at 3 public health service COVID-19 test sites in the Netherlands between December 21, 2021, and February 10, 2022. Participants had a swab sample taken for reverse transcription polymerase chain reaction (RT-PCR) testing and then were given an at-home test within 3 hours to confirm results.

The evaluated tests were Flowflex (Acon Laboratories), MPBio (MP Biomedicals), and Clinitest (Siemens-Healthineers). The main outcomes were sensitivity, specificity, and positive and negative predictive values of each self-test, with RT-PCR testing as the reference standard, according to the study.

Overall, results showed that the sensitivity of the 3 rapid antigen tests decreased as omicron transitioned from accounting for 29% of infections to more than 95% of infections. According to Schuit et al, sensitivity declined from 87% to 81% for Flowflex, 83% to 76% for MPBio, and 80% to 67% for Clinitest, with only Clinitest reaching statistical significance. Additional oropharyngeal to nasal self-sampling—which was done only for MPBio and Clinitest—showed an improvement in the sensitivity from 70% to 83% for MPBio and 70% to 77% for Clinitest. Investigators noted that this improvement was most evident in persons who visited the test site for reasons other than to confirm a positive self-test result.

“We found that the performance of rapid antigen tests with nasal self-sampling declined during the period omicron emerged. We also showed that the performance of rapid antigen tests can be improved by adding oropharyngeal to nasal self-sampling,” wrote researchers. “Therefore, after proper evaluation, manufacturers of rapid antigen tests should consider extending their instructions for use to include combined oropharyngeal and nasal self-sampling.”