On-field evaluation of a ultra-rapid fluorescence immunoassay as a frontline test for SARS-COV-2 diagnostic

Orsi, Andrea; Pennati, Beatrice Marina; Bruzzone, Bianca; Ricucci, Valentina; Ferone, Diego; Barbera, Paolo; Arboscello, Eleonora; Dentone, Chiara; Icardi, Giancarlo

BACKGROUND: Viral RNA amplification by real-time RT-PCR still represents the gold standard for the detection of SARS-CoV-2, but the development of rapid, reliable and easy-to-perform diagnostic methods is crucial for public health, because of the need of shortening the time of result-reporting with a cost-efficient approach. OBJECTIVES: The aim of our research was to assess the performance of FREND(TM) COVID-19 Ag assay (NanoEntek, South Korea) as a ultra-rapid frontline test for SARS-COV-2 identification, in comparison with RT-PCR and another COVID-19 antigen fluorescence immunoassay (FIA). STUDY DESIGN: The qualitative FIA FREND(TM) test, designed to detect within 3 minutes the Nucleocapsid protein of SARS-CoV-2, was evaluated using nasopharyngeal swabs in Universal Transport Medium (UTM™, Copan Diagnostics Inc, US) from suspected COVID-19 cases who accessed the Emergency Room of the Ospedale Policlinico San Martino, Genoa, Liguria, Northwest Italy. Diagnostic accuracy was determined in comparison with SARS-CoV-2 RT-PCR and STANDARD F(TM) COVID-19 Ag FIA test (SD BIOSENSOR Inc., Republic of Korea). RESULTS: In November 2020, 110 nasopharyngeal samples were collected consecutively; 60 resulted RT-PCR positive. With respect to RT-PCR results, sensitivity and specificity of FREND(TM) COVID-19 Ag test were 93.3% (95% CI: 83.8-98.2) and 100% (95% CI: 92.9-100), respectively. FREND(TM) and STANDARD F(TM) COVID-19 Ag FIA assays showed a concordance of 96.4% (Cohen’s k = 0.93, 95% CI: 0.86-0.99). CONCLUSIONS: FREND(TM) FIA test showed high sensitivity and specificity in nasopharyngeal swabs. The assay has the potential to become an important tool for an ultra-rapid identification of SARS-COV-2 infection, particularly in situations with limited access to molecular diagnostics.