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?:abstract
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Background: RT-PCR on nasopharyngeal (NPS)/oropharyngeal swabs is the gold standard for diagnosis of SARS-CoV-2 infection and viral load monitoring Oral fluid (OF) is an alternate clinical sample, easy and safer to collect and could be useful for COVID-19 diagnosis, monitoring viral load and shedding Methods: Optimal assay conditions and analytical sensitivity were established for the commercial Simplexa™ COVID-19 Direct assay adapted to OF matrix The assay was used to test 337 OF and NPS specimens collected in parallel from 164 hospitalized patients;50 bronchoalveolar lavage (BAL) specimens from a subgroup of severe COVID-19 cases were also analysed Results: Using Simplexa™ COVID-19 Direct on OF matrix, 100% analytical detection down to 1 TCID50/mL (corresponding to 4 × 103 copies (cp)/mL) was observed No crossreaction with other viruses transmitted through the respiratory toute was observed Parallel testing of 337 OF and NPS samples showed highly concordant results (κ = 0 831;95 % CI = 0 771–0 891), and high correlation of Ct values (r = 0 921;p <0 0001) High concordance and elevated correlation was observed also between OF and BAL Prolonged viral RNA shedding was observed up to 100 days from symptoms onset (DSO), with 32% and 29% positivity observed in OF and NPS samples, respectively, collected between 60 and 100 DSO Conclusions: Simplexa™ COVID-19 Direct assays on OF have high sensitivity and specificity to detect SARS-CoV-2 RNA and provide an alternative to NPS for diagnosis and monitoring SARS-CoV-2 shedding
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