Rapid Determination of SARS-CoV-2 Antibodies Using a Bedside, Point-of-Care, Serological Test

Abstract

BACKGROUND: Despite over 70 rapid diagnostic tests (RDT) for SARS-CoV-2 currently in some stage of development or use, many have failed, few have been validated on more than a few samples, and none provide medical practitioners with an easy-to-use, self-contained, bedside test with high accuracy. METHODS: Two hundred fifty-six sera from 101 patients hospitalized with SARS-CoV-2 infection (positive RT-PCR) were tested for IgM and IgG using the NG-Test IgM-IgG COVID all-in-one assay (NG Biotech). The seroconversion dynamic was assessed by symptom onset and the day of RT-PCR diagnosis. Fifty control sera were also tested to assess specificity. FINDINGS: The NG-Test IgM-IgG COVID All-in-one identified 16.8% of RT-PCR-positive patients as SARS-CoV-2 the day PCR testing was performed, but specific IgM and/or IgGs were detected in over 50% and 98% of patients at 8 and 15 days after the onset of symptoms, respectively. Sensitivity, specificity, Positive Predictive Value and Negative Predictive Value were 97·0%, 100%, 100% and 96·2%, respectively 15 days after the onset of symptoms. No difference in seroconversion delay was observed regardless of whether patients received ventilation. INTERPRETATION: This valuable serological assay could serve as a complementary source of diagnostic information to RT-PCR and chest imaging. It may also be useful to monitor medical and non-medical workers during the ongoing pandemic or during subsequent waves, and to monitor the immunological status of the general population after social distancing measures have eased. The assay can be used as a bedside tool or used in a general practitioner’s office. FUNDING STATEMENT: This research was supported by Assistance Publique – Hopitaux de Paris (APHP), Medecins Sans Frontieres (MSF), and by a Grant from the French Defence Innovation Agency (AID). DECLARATION OF INTERESTS: The authors declare no conflict of interest. ETHICS APPROVAL STATEMENT: The use of samples was reviewed and approved by the local Ethics Committee under CPP N° CO-15-000.