Rapid Determination of SARS-CoV-2 antibodies using a bedside, point-of-Care, serological test

Emerg Microbes Infect. 2020 Dec;9(1):2212-2221. doi: 10.1080/22221751.2020.1826892.


Background: Several serological tests for SARS-CoV-2 have been developed or use, but most have only been validated on few samples, and none provide medical practitioners with an easy-to-use, self-contained, bedside test with high accuracy. Material and methods: Two-hundred fifty-six sera from 101 patients hospitalized with SARS-CoV-2 infection (positive RT-PCR) and 50 control sera were tested for IgM/IgG using the NG-Test IgM-IgG COVID all-in-one assay. The seroconversion dynamic was assessed by symptom onset and day of RT-PCR diagnosis. Results: Among the SARS-CoV-2 infected patients, positive IgG and/or IgM result was observed for 67.3% of patients (68/101), including 17 (16.8%) already positive at the day of RT-PCR, and 51 (50.5%) with observable seroconversion, and 32.7% (33/101) remained negative as subsequent sampling was not possible (patient discharge or death). The sensitivity increased with the delay between onset of symptoms and sampling, going from 29.1%, 78.2% and 86.5% for the time periods of 0-9-, 10-14- and >14-days after the onset of symptoms, respectively. Cumulative 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. Conclusions: The NG-test is a bedside serological assay that could serve as a complementary source of diagnostic information to RT-PCR and chest imaging. It may also be useful to monitor immunological status of medical and non-medical workers during the ongoing pandemic, and the general population after social distancing measures have eased.

Keywords: COVID-19; Diagnostics; bedside; diagnosis; rapid test; serology.

MeSH terms

  • Adult
  • Antibodies, Viral / blood
  • Antibodies, Viral / immunology*
  • Betacoronavirus / genetics
  • Betacoronavirus / immunology*
  • COVID-19
  • COVID-19 Testing
  • Case-Control Studies
  • Clinical Laboratory Techniques*
  • Coronavirus Infections / diagnosis*
  • Coronavirus Infections / immunology*
  • Coronavirus Infections / virology
  • Female
  • Humans
  • Immunoglobulin G / blood
  • Immunoglobulin G / immunology
  • Immunoglobulin M / blood
  • Immunoglobulin M / immunology
  • Male
  • Middle Aged
  • Pandemics
  • Pneumonia, Viral / diagnosis*
  • Pneumonia, Viral / immunology*
  • Pneumonia, Viral / virology
  • Point-of-Care Testing*
  • Polymerase Chain Reaction
  • Reagent Strips
  • SARS-CoV-2
  • Sensitivity and Specificity
  • Seroconversion
  • Serologic Tests / methods*
  • Serologic Tests / standards


  • Antibodies, Viral
  • Immunoglobulin G
  • Immunoglobulin M
  • Reagent Strips

Grant support

This research was supported by Assistance Publique Hôpitaux de Paris (APHP), Médecins Sans Frontières (MSF) and by a Grant from the French Defence Innovation Agency (AID); Ministère de la Défense.