Anterior nasal versus nasal mid-turbinate sampling for a SARS-CoV-2 antigen-detecting rapid test: does localisation or professional collection matter?

Infect Dis (Lond). 2021 Aug 27;1-6. doi: 10.1080/23744235.2021.1969426. Online ahead of print.

Abstract

Introduction: Most SARS-CoV-2 antigen-detecting rapid diagnostic tests require nasopharyngeal sampling, which is frequently perceived as uncomfortable and requires healthcare professionals, thus limiting scale-up. Nasal sampling could enable self-sampling and increase acceptability. The term nasal sampling is often not used uniformly and sampling protocols differ.

Methods: This manufacturer-independent, prospective diagnostic accuracy study, compared professional anterior nasal and nasal mid-turbinate sampling for a WHO-listed SARS-CoV-2 antigen-detecting rapid diagnostic test. The second group of participants collected a nasal mid-turbinate sample themselves and underwent a professional nasopharyngeal swab for comparison. The reference standard was real-time polymerase chain reaction (RT-PCR) using combined oro-/nasopharyngeal sampling. Individuals with high suspicion of SARS-CoV-2 infection were tested. Sensitivity, specificity, and percent agreement were calculated. Self-sampling was observed without intervention. Feasibility was evaluated by observer and participant questionnaires.

Results: Among 132 symptomatic adults, both professional anterior nasal and nasal mid-turbinate sampling yielded a sensitivity of 86.1% (31/36 RT-PCR positives detected; 95%CI: 71.3-93.9) and a specificity of 100.0% (95%CI: 95.7-100). The positive percent agreement was 100% (95%CI: 89.0-100). Among 96 additional adults, self nasal mid-turbinate and professional nasopharyngeal sampling yielded an identical sensitivity of 91.2% (31/34; 95%CI 77.0-97.0). Specificity was 98.4% (95%CI: 91.4-99.9) with nasal mid-turbinate and 100.0% (95%CI: 94.2-100) with nasopharyngeal sampling. The positive percent agreement was 96.8% (95%CI: 83.8-99.8). Most participants (85.3%) considered self-sampling as easy to perform.

Conclusion: Professional anterior nasal and nasal mid-turbinate sampling are of equivalent accuracy for an antigen-detecting rapid diagnostic test in ambulatory symptomatic adults. Participants were able to reliably perform nasal mid-turbinate sampling themselves, following written and illustrated instructions. Nasal self-sampling will facilitate scaling of SARS-CoV-2 antigen testing.

Keywords: COVID-19; SARS-CoV-2; anterior nasal; antigen-detecting rapid test; nasal mid-turbinate; nasal-sampling; self-sampling.

Grant support

C.M. Denkinger reports grants from Foundation for Innovative New Diagnostics (FIND), and Ministry of Science, Research and Culture, State of Baden Wuerttemberg, Germany, to conduct of the study. J.A. Sacks reports grants from UK Department for International Development (DFID, recently replaced by FCMO), World Health Organisation (WHO) and Unitaid, to conduct of the study. FIND supplied the test kits for the study. The study was supported by Heidelberg University Hospital and Charité University Hospital internal funds.