Sysmex Journal International

2022Vol.32 No.1


A Novel Highly Quantitative and Reproducible Assay for the Detection of Anti-SARS-CoV-2 IgG and IgM Antibodies


Kenta NODA*1, Kouki MATSUDA*2, Shigehiro YAGISHITA*3, Kenji MAEDA*2,
Satoshi IWATA*8, Kazuto YAMASHITA*1, Yusuke ATARASHI*1, Shunsuke WATANABE*1, Nobuyuki IDE*9, Tomokazu YOSHIDA*1, Norio OHMAGARI*4, Hiroaki MITSUYA*2,10,11 and Akinobu HAMADA*3

*1 Central Research Laboratories, Sysmex Corporation
*2 Department of Refractory Viral Infections, National Center for Global Health and Medicine (NCGM) Research Institute
*3 Division of Molecular Pharmacology, National Cancer Center Research Institute
*4 Disease Control and Prevention Center (DCC), NCGM
*5 Center for Clinical Science, NCGM
*6 Respiratory Medicine, NCGM Center Hospital
*7 Department of Laboratory Medicine, National Cancer Center Hospital
*8 Department of Infectious Diseases, National Cancer Center Hospital
*9 Bio‑Diagnostic Reagent Technology Center, Sysmex Corporation
*10 Experimental Retrovirology Section, HIV and AIDS Malignancy Branch, National Cancer Institute, National Institutes of Health
*11 Department of Clinical Sciences, Kumamoto University Hospital


The quantitative range and reproducibility of current serological tests for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) are not optimized. Herein, we developed a diagnostic test that detects SARS-CoV-2 IgG and IgM with high quantitativeness and reproducibility and low interference. The system was based on the high-sensitivity chemiluminescence enzyme immunoassay (HISCL) platform and detects IgG and IgM specific to SARS-CoV-2 spike and nucleocapsid proteins. Quantification accuracy and reproducibility were evaluated using serially diluted samples from 60 SARS-CoV-2-infected patients. Assay performance was evaluated using serum samples from the SARS-CoV-2-infected patients and 500 SARS-CoV-2-negative serum samples collected before the emergence of SARS-CoV-2. The system showed high quantification accuracy (range, 102), high reproducibility (within 5%), and no cross-reaction between SARS1- and MERS-S proteins. Detection accuracy was 98.3% and 93.3% for IgG and IgM against spike proteins and 100% and 71.7% for IgG and IgM against nucleocapsid proteins, respectively. Mean antibody levels were > 10 times that in negative samples upon admission and > 100 times that at convalescent periods. Clinical severity upon admission was not correlated with IgG or IgM levels. This highly quantitative, reproducible assay system with high clinical performance may help analyze temporal serological/ immunological profiles of SARS-CoV-2 infection and SARS-CoV-2 vaccine effectiveness.


This article is republished from Scientific Reports, Vol.11, 5198, 04 March 2021, which is licensed under a Creative Commons Attribution 4.0 International License.
HISCL SARS-CoV-2 S-IgG reagent is for research use only. HISCL SARS-CoV-2 N-IgG reagent, HISCL SARSCoV-2 N-IgM reagent and HISCL SARS-CoV-2 S-IgM reagent are not for sale.