Since SARS-CoV-2-based disease (COVID-19) spreads as a pandemic, the necessity of a highly sensitive molecular diagnosis that can drastically reduce false negatives reverse transcription PCR (rtPCR) results, raises as a major clinical need. Here we evaluated the performance of a ddPCR-based assay to quantify SARS-CoV-2 titer in 55 suspected COVID-19 cases with negative rtPCR results thanks to in-house ddPCR assay (targeting RdRp and host RNaseP). Samples were collected at ASST-GOM Niguarda between February and May 2020 at hospital admission. Clinical and imaging data were obtained for clinical staging and definition of disease severity. Patients were mainly female (45.5%) with a median age of 73 (57–84) years. ddPCR-based assay detected SARS-CoV-2 genome in nasopharyngeal samples of 19 (34.5%) patients (median viral-load: 128 copies/mL, IQR: 72–345). In 15 of them (78.9%), chest CT showed a classical COVID-19 bilateral interstitial pneumonia; 14 patients (73.7%) showed severe COVID-19 manifestations. ddPCR did not identify any trace of SARS-CoV-2 genome in the respiratory samples of the remaining 36 patients. The serological assay performed in a subgroup of 34 patients at the later stage of illness (from 3 days to 90 days after) confirmed the presence of SARS-CoV-2 antibodies in all patients tested positive for SARS-CoV-2 in ddPCR (100%). Contrariwise, negative tests were observed in 95.0% ddPCR negative patients (P<0.001). Thanks to a ddPCR-based assay, we achieved a rapid and accurate SARS-CoV-2 diagnosis in rtPCR-negative respiratory samples of individuals with COVID-19 suspect, allowing the rapid taking care and correct management of these patients.
【초록키워드】 COVID-19, SARS-CoV-2, pandemic, disease severity, Diagnosis, Spread, Serological assay, SARS-CoV-2 antibody, Chest CT, Molecular diagnosis, SARS-CoV-2 genome, clinical, management, female, Patient, RdRP, Hospital admission, reverse transcription PCR, disease, Care, patients, False negative, COVID-19 case, median age, positive, negative test, nasopharyngeal sample, Host, respiratory sample, interstitial, RNAseP, severe COVID-19 manifestations, raise, tested, classical, identify, performed, collected, Sample, evaluated, median, reduce, individuals with COVID-19, 【제목키워드】 SARS-CoV-2, detection, Nasopharyngeal swab, digital PCR, Real-time PCR, quantification, COVID-19 patient,