# Diagnostic accuracy of self-collected anterior nasal swabs for SARS-CoV-2 RT-PCR testing

## TL;DR

The study found that self-collected nasal swabs are a reliable alternative to healthcare professional-collected swabs for SARS-CoV-2 testing.

## Contribution

The study demonstrates that self-collected anterior nasal swabs have acceptable diagnostic accuracy for SARS-CoV-2 PCR testing.

## Key findings

- Self-collected ANS swabs had 84–88.0% sensitivity and 97–98% specificity compared to HCP-collected CTN swabs.
- The mean Ct value difference between ANS and CTN swabs was ~2 cycles, with discordant results having higher Ct values.
- Sensitivity of ANS swabs decreased over time, but specificity remained consistent.

## Abstract

This prospective sub-study aimed to compare the diagnostic accuracy of the self-collected anterior nasal swab (ANS; Rhinoswab) against that of healthcare professional (HCP)-collected combined throat and nasal swab (CTN). Eligibility criteria for the study included: >5 years of age, a positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) rapid antigen or PCR <72 h prior, and one other participating household member. Samples were tested via reverse transcription polymerase chain reaction (RT-PCR) and included in the analysis where RS and CTN swab were collected on the same day. Indeterminate results were excluded from the analysis. Sensitivity and specificity were used to assess the accuracy of results from self-collected RS. Analysis of the average cycle threshold (Ct) was performed in GraphPad Prism using a paired t-test (P-value < 0.05, 95% confidence interval [CI]) to assess if there was a significant difference in the Ct values between the HCP-collected CTN swab and the self-collected RS. In total, 583 single-prong result-pairs and 276 double-prong result-pairs were analyzed after exclusion of indeterminate results. The sensitivity of the RS was 84–88.0%, and the specificity was 97–98%. The mean difference in Ct value between the CTN and ANS was ~2 cycles (P < 0.005, ~2.5 CI 95%) with the raw Ct value of discordant results ~10 Ct values higher than concordant results. Furthermore, the sensitivity from days 1 to 10 was 91–96 to 58–69%, while specificity stayed consistent. Overall, our data support the use of the RS as an alternative nasal sampling tool to traditional CTN swabs collected by HCP.

In this study, we compared the PCR results of self-collected anterior nasal swabs against healthcare professional-collected combined throat and nasal swabs. The sensitivity and specificity of the anterior nasal swab were considered acceptable when compared to World Health Organization recommendations. The sensitivity of the Rhinoswab ANS was higher at the beginning of the trial when compared with the final day of the trial, regardless of the number of prongs tested via PCR. The self-collected Rhinoswab is a valid tool for community screening of severe acute respiratory syndrome coronavirus 2 in vulnerable populations.