Diagnostic Accuracy of SARS-CoV-2 Rapid Antigen Test (Oral Fluid) with Unsupervised Self-sampling in the Omicron Period

Background: To assess the performance of rapid antigen tests between unsupervised oral fluid self-sampling and nasal self-sampling during the omicron period. Objective: To diagnostically validate SARS-CoV-2 Rapid Antigen Test (Oral Fluid) by comparing results with those of nasal self-sampling in the omicron period. Method: Run rapid in vitro diagnostic tests for detection of antigen to SARS-CoV-2 in nasal and oral fluid sampling, compared to a leading commercial test using clinical specimens for validation of performance. Result: When nasal self-sampling compared with nasal self-sampling, sensitivities were found to be slightly higher in confirmatory testers. Sensitivity (94.3%): In total 297 PCR in the Clinitest group were confirmatory testers (previously tested positive by a self-test at own initiative), 280 PCR confirmed positive samples were correctly detected by SARS-CoV-2 (COVID-19) Rapid Test (Oral Fluid). 17 false negative cases were reported. Specificity (99.4%): In total 350 PCR confirmed negative samples were correctly detected by SARS-CoV-2 (COVID-19) Rapid Test (Oral Fluid). Only 2 false positive cases were reported.Accuracy (97.1%): In total 649 PCR confirmed samples: 630 PCR confirmed samples were correctly detected by SARS-CoV-2 (COVID-19) Rapid Test (Oral Fluid). Among which, overall sensitivities with nasal self-sampling were 79.0% (95% confidence interval 74.7% to 82.8%) for SARS-CoV-2 by Rapid Antigen Tests on Saliva. Sensitivities were substantially higher in confirmatory testers with Citest SARS-CoV-2 Rapid Antigen Test (Oral Fluid) than in those who tested for other reasons.Conclusion: Sensitivities of three rapid antigen tests with nasal self-sampling decreased during the emergence of omicron but was only statistically significant for Clinitest. Sensitivities appeared to be substantially influenced by the proportion of confirmatory testers. Sensitivities of Citest SARS-CoV-2 Rapid Antigen Test improved after the addition of Oral Fluid self-sampling. A positive self-test result justifies prompt self-isolation without the need for confirmatory testing. Individuals with a negative self-test result should adhere to general preventive measures because a false negative result cannot be ruled out.