Time course of the sensitivity and specificity of anti-SARS-CoV-2 IgM and IgG antibodies for symptomatic COVID-19 in Japan

Abstract

The accurate and prompt diagnosis of SARS-CoV-2 infection is required for the control and treatment of the coronavirus infection disease 2019 (COVID-19). In this study, we aimed to investigate the time courses of the anti-severe acute corona respiratory syndrome coronavirus 2 (SARS-CoV-2) IgM and IgG titers and to evaluate the sensitivity and specificity of such tests according to the specific day after the onset of COVID-19 among a patient population in Japan. We measured the titers of SARS-CoV-2 IgM and IgG in sera from 105 subjects, including 26 symptomatic COVID-19 patients, using chemiluminescent immunoassay (CLIA) methods utilizing magnetic beads coated with SARS-CoV-2 nucleocapsid protein and spike protein. The results of a ROC analysis suggested the possibility that the cutoff values in Japan might be lower than the manufacturer’s reported cutoff (10 AU/mL): 1 AU/mL for IgM and 5 AU/mL for IgG. The sensitivity of the test before Day 8 after symptom onset was less than 50%; at Days 9–10, however, we obtained a much higher sensitivity of 81.8% for both IgM and IgG. At 15 days or later after symptom onset, the SARS-CoV-2 IgG test had a sensitivity of 100%. These results suggest that if the number of days since disease onset is taken into consideration, these antibody tests could be very useful for the diagnosis of COVID-19 and similar diseases.

Serologic Survey of IgG Against SARS-CoV-2 Among Hospital Visitors Without a History of SARS-CoV-2 Infection in Tokyo, 2020–2021

“…According to the manufacturer's instructions, ≥10 arbitrary units (AU)/mL is considered positive. The sensitivity of the iFlash-SARS-CoV-2 IgG kit is 63.6% for RT-PCR-positive patients 9 to 10 days after symptom onset and 100% for RT-PCR-positive patients ≥15 days after symptom onset, whereas the specificity of the kit is 100% for samples from RT-PCR-negative patients 11 . Parai et al reported sensitivity and specificity values of 76.9% and 100%, respectively, for the iFlash-SARS-CoV-2 IgG kit 12 .…”

Diagnosing COVID‐19 in human sera with detected immunoglobulins IgM and IgG by means of Raman spectroscopy

“…Therefore, IgG is commonly used to indicate past infection. [ 7 , 8 ] Despite researches showed that IgG may persist for months, [ 8 , 9 ] there are still no studies claiming about permanent immunity [ 10 ] mostly because of the novelty of the COVID‐19. In addition, a positive correlation can be found between the antibody levels and disease severity.…”

Epidemiological study using IgM and IgG antibody titers against SARS-CoV-2 in The University of Tokyo, Japan (UT-CATS)

“…Most of the significant differences in the present study are among values below the cutoffs, and there was some discrepancy in the results. On the other hand, there are some reports suggesting the higher or lower cutoff value [15,29,30], and the cutoff value itself for this emerging infectious disease is still under the validation process especially in asymptomatic subjects, which might be changed in future. Further study is needed to confirm the quantitative meanings of these values.…”

“…Nakano et al analyzed the antibody titers of Japanese patients with symptomatic COVID-19, and suggested that the cutoff values in Japan might be lower than the manufacturer's reported cutoff [15]. Using the cutoff value of 5AU/mL, the number of positive participants for IgM was 42 (0.64%), and one for IgG was 70 (1.06%).…”