Rapid diagnosis of SARS-CoV-2 infection by detecting IgG and IgM antibodies with an immunochromatographic device: a prospective single-center study

ABSTRACT

ObjectivesSARS-CoV-2 infection diagnosis is challenging in patients from 2-3 weeks after the onset of symptoms, due to the low positivity rate of the PCR. Serologic tests could be complementary to PCR in these situations. The aim of our study was to analyze the diagnostic performance of one serologic rapid test in COVID-19 patients. MethodsWe evaluated an immunochromatographic test (AllTest COVID-19 IgG / IgM) which detects IgG and IgM antibodies. We validated the serologic test using serum samples from 45 negative patients (group 1) and 55 patients with COVID-19 confirmed by PCR (group 2). Then, we prospectively evaluated the test in 63 patients with clinical diagnosis of pneumonia of unknown etiology that were COVID-19 negative by PCR (group 3). ResultsAll 45 patients from group 1 were negative for the serologic test (specificity = 100%). Regarding group 2 (PCR-positive), the median time from their symptom onset until testing was 11 days. For these 55 group-2 patients, the test was positive for either IgM or IgG in 26 (overall sensitivity = 47%), and in patients tested 14 days or more after the onset of symptoms, the sensitivity was 74%. Regarding the 63 group-3 patients, median time after symptom onset was 17 days, and the test was positive in 56 (89% positivity). ConclusionsOur study shows that serologic rapid tests could be used as a complement of PCR to diagnose SARS-CoV-2 infection after 14 days from the onset of symptoms and in patients with pneumonia and negative PCR for SARS-CoV-2.