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

Nikolai, Olga; Rohardt, Chiara; Tobian, Frank; Junge, Andrea; Corman, Victor M.; Jones, Terry C.; Gaeddert, Mary; Lainati, Federica; Sacks, Jilian A.; Seybold, Joachim; Mockenhaupt, Frank P.; Denkinger, Claudia M.; Lindner, Andreas K.

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.