Performance of six rapid diagnostic tests for SARS-CoV-2 antigen detection and implications for practical use.

BACKGROUND: Direct detection of SARS-CoV-2 viral proteins in nasopharyngeal swabs using lateral flow immunoassays is a simple, fast and cheap approach to diagnose the infection. AIMS AND METHODS: The performance of 6 SARS-CoV-2 antigen rapid diagnostic tests has been assessed in 634 hospitalized patients or outpatients including 297 patients found to be positive for SARS-CoV-2 RNA by means of RT-PCR and 337 patients presumed to be SARS-CoV-2 RNA-negative. RESULTS: The specificity of SARS-CoV-2 RDTs was generally high (398.5%). One assay had a lower specificity of 93.2%. The overall sensitivity of the 6 RDTs was variable, from 32.3% to 61.7%. Sensitivity correlated with the delay of sampling after the onset of symptoms and the viral load estimated by the Ct value in RT-PCR. Four out of 6 RDTs tested achieved sensitivities 380% when clinical specimens were collected during the first 3 days following symptom onset or with a Ct value ≤25. CONCLUSIONS: The present study shows that SARS-CoV-2 antigen can be easily and reliably detected by RDTs. These tests are easy and rapid to perform. However, the specificity and sensitivity of COVID-19 antigen RDTs may widely vary across different tests and must therefore be carefully evaluated before releasing these assays for realworld applications.

Viral genomic, metagenomic and human transcriptomic characterization and prediction of the clinical forms of COVID-19.

COVID-19 is characterized by respiratory symptoms of various severities, ranging from mild upper respiratory signs to acute respiratory failure/acute respiratory distress syndrome associated with a high mortality rate. However, the pathophysiology of the disease is largely unknown. Shotgun metagenomics from nasopharyngeal swabs were used to characterize the genomic, metagenomic and transcriptomic features of patients from the first pandemic wave with various forms of COVID-19, including outpatients, patients hospitalized not requiring intensive care, and patients in the intensive care unit, to identify viral and/or host factors associated with the most severe forms of the disease. Neither the genetic characteristics of SARS-CoV-2, nor the detection of bacteria, viruses, fungi or parasites were associated with the severity of pulmonary disease. Severe pneumonia was associated with overexpression of cytokine transcripts activating the CXCR2 pathway, whereas patients with benign disease presented with a T helper "Th1-Th17" profile. The latter profile was associated with female gender and a lower mortality rate. Our findings indicate that the most severe cases of COVID-19 are characterized by the presence of overactive immune cells resulting in neutrophil pulmonary infiltration which, in turn, could enhance the inflammatory response and prolong tissue damage. These findings make CXCR2 antagonists, in particular IL-8 antagonists, promising candidates for the treatment of patients with severe COVID-19.