Diagnostic accuracy of an automated chemiluminescent immunoassay for anti‐SARS‐CoV‐2 IgM and IgG antibodies: an Italian experience

Abstract

A pandemic of coronavirus disease 2019 caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been spreading throughout the world. Though molecular diagnostic tests are the gold standard for COVID-19, serological testing is emerging as a potential surveillance tool, in addition to its complementary role in COVID-19 diagnostics. Indubitably quantitative serological testing provides greater advantages than qualitative tests but today there is still little known about serological diagnostics and what the most appropriate role quantitative tests might play. Sixty-one COVID-19 patients and 64 patients from a control group were tested by iFlash1800 CLIA analyzer for anti-SARS CoV-2 antibodies IgM and IgG. All COVID-19 patients were hospitalized in San Giovanni di Dio Hospital (Florence, Italy) and had a positive oro/nasopharyngeal swab reversetranscription polymerase chain reaction result. The highest sensitivity with a very good specificity performance was reached at a cutoff value of 10.0 AU/mL for IgM and of 7.1 for IgG antibodies, hence near to the manufacturer's cutoff values of 10 AU/mL for both isotypes. The receiver operating characteristic curves showed area under the curve values of 0.918 and 0.980 for anti-SARS CoV-2 antibodies IgM and IgG, respectively. iFlash1800 CLIA analyzer has shown highly accurate results for the anti-SARS-CoV-2 antibodies profile and can be considered an excellent tool for COVID-19 diagnostics.

High-Accuracy Multiplexed SARS-CoV-2 Antibody Assay with Avidity and Saliva Capability on a Nano-Plasmonic Platform

“…Highly accurate detection of antibodies against SARS-CoV-2 is crucial to combating the pandemic by aiding diagnosis and assessing infection timing, prevalence, duration of antibody response, and potential immunity. Thus far, a variety of antibody tests have been developed using lateral flow rapid tests, enzyme-linked immunosorbent assay (ELISA) and chemiluminescence (CLIA) platforms, including ones authorized by the U.S. Food and Drug Administration (FDA) for emergency use 2,[13][14][15][16][17][18][19][20][21] . Despite the progress, few assays differentiate antibody subtypes to glean infection timing with > 99.5 % specificity for both IgG and IgM 22,23 .…”

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

“…Consequently, the cutoff values in the Japanese population could be lower (1 or 2 AU/mL for IgM and 5 AU/mL for IgG) than the manufacturer's cutoff value (10 AU/mL). In previous studies in which the same CLIA-based assays were used, the false-positive rates for the IgM and IgG tests were reported to be 0% (0/33) and 9.1% (3/33) in an Italian study 7 and 9.1% (4/44) and 0% (0/44) in a Chinese study 16 , respectively, which are somewhat higher than those in the present study (2.9 % [1/34] and 0 % [0/34]). One of the mechanisms for false-positive results might be the presence of autoimmune diseases, and the prevalences of autoimmune diseases differ among population.…”

In-Utero Mother-to-Child SARS-CoV-2 Transmission: Viral Detection and Fetal Immune Response

“…It was previously reported that the absence of IgM and IgG in the milk is not uncommon, especially in the case of respiratory viruses 29 . A recent study showed the high sensitivity and speci city of iFlash automated system for antibodies detection 23 . However, this methodology has been adapted for detection of antibodies in milk and the sensitivity may be attenuated on this particular specimen.…”

“…The presence of SARS-CoV-2 speci c antibodies was investigated using SARS-CoV-2 IgG and IgM chemiluminescence immunoassay (CLIA) kits on fully automated iFlash1800 analyzer (Shenzen YHLO Biotech Co., Ltd., Shenzen, China): the assay uses Nucleocapsid (N) and Spike (S) viral proteins as magnetic beads coating antigens. The value of 10.0 AU/mL was used as positivity cut-off for IgM, while 7.1 for IgG 23 .…”