Detection of COVID-19-Suspected Cases from a SARS-CoV-2-PCR Negative Group of an In-Hospital Cluster by Anti-SARS-CoV-2 Antibodies

Abstract

We investigated anti-SARS-CoV-2 IgG and IgM in 9 subjects who were selected as with shadows on the lungs in chest computed tomography from 17 symptomatic subjects from 213 SARS-CoV-2-PCR-negative subjects in total of 266 subjects for the investigation of an in-hospital COVID-19 cluster in St. Marianna University Yokohama Seibu Hospital. Anti-SARS-CoV-2 IgM and IgG antibodies were investigated in the 5th, 7th, 11th, and 19th weeks after the exposure to SARS-CoV-2. Anti-SARS-CoV-2 IgM were positive in 2 out of the 9 cases from the 5th week but were negative in all the 9 cases in the 11th and 19th weeks. Anti-SARS-CoV-2 IgG were positive in 5 out of the 9 cases from the 5th week, being elevated to the largest values in the 5th or 7th weeks in all the 5 cases. Analyses for anti-SARS-CoV-2 antibodies may be valuable as an adjunct in the diagnosis of COVID-19 specifically for the detection of the symptomatic but SARS-CoV-2-PCR-negative patients in an in-hospital COVID-19 cluster.