Diagnostic agreement between Rhinoswabs and joint nose and throat swabs for the detection of influenza and SARS-CoV-2 among symptomatic ambulatory patients in Hong Kong.

Abstract

Accurate detection of respiratory viruses relies on appropriate sample collection, but whether joint nose and throat sampling is necessary for high diagnostic performance or whether nose sampling alone can provide comparable results remains uncertain. We evaluated the diagnostic agreement between joint nose and throat swabs (NTS) and Rhinoswab (RhinoMed, Cremorne, Australia), a novel anterior nasal swab for RT-qPCR detection of respiratory viruses among symptomatic outpatients. Outpatients with febrile acute respiratory illness were enrolled at a clinic in Hong Kong and paired joint NTS and Rhinoswab samples were tested by reverse transcription polymerase chain reaction (RT-qPCR) for influenza A, influenza B, SARS-CoV-2 and human ribonuclease P (RNase P) as an internal control. Diagnostic agreement and RT-qPCR Ct values were compared between the paired samples. Between May 2023 and April 2024, 488 participants provided paired samples. Overall concordance between Rhinoswab and NTS was 98.0% (95% CI: 96.3% to 99.0%) for influenza A, 99.0% (95% CI: 97.6% to 99.7%) for influenza B, and 99.0% (95% CI: 97.6% to 99.7%) for SARS-CoV-2. Cohen's kappa also indicated high agreement for all viruses: 0.95 (95% CI: 0.92 to 0.98) for influenza A, 0.94 (95% CI: 0.88 to 0.99) for influenza B, and 0.92 (95% CI: 0.85 to 0.99) for SARS-CoV-2. Ct values from Rhinoswab were moderately correlated with NTS for all three viruses and RNase P. The majority of discordant samples had Ct values of 30 and above (16/18, 88.9%). Rhinoswabs achieved high agreement with joint NTS for RT-qPCR detection of influenza and SARS-CoV-2. Given their minimal invasiveness Rhinoswabs are a viable alternative specimen type for supervised respiratory virus testing.