Determinazione degli anticorpi IgM e IgG anti-SARS-CoV-2 mediante piattaforma iFlash1800 CLIA in una casistica italiana
Detection of IgG and IgM anti-SARS-CoV-2 by iFlash1800 CLIA analyser in an Italian population

AUTORI

ABSTRACT

Detection of IgG and IgM anti-SARS-CoV-2 by iFlash1800 CLIA analyser in an Italian population

Introduction: World Health Organization guidance dated 17 January 2020 indicates the need to associate the detection of antibodies anti-SARS-CoV-2 to real time reverse transcriptase PCR test (rRT-PCR) for the diagnosis of the new coronavirus infection. Aim of this study is to acquire information about the prevalence of IgG and IgM anti-SARS-CoV-2 antibodies in a population of health workers (control group) and in patients affected by COVID-19.
Methods: the control group includes 190 asymptomatic health workers; the patient group includes 44 affected patients. Serum IgM and IgG antibodies to SARS-CoV-2 were measured by using iFlash1800, a fully automatic chemiluminescence immunoassay analyser. rRT-PCR was performed with CFX96 TouchTM system (Bio-Rad, Hercules, California, USA) and LightCycler 480 Real-Time PCR System (Roche Diagnostics, Mannheim, Germania).
Results 186 out of 190 asymptomatic health workers were negative for rRT-PCR. Among these, 3 were positive for IgG antibodies (98% specificity, 95%CI 96-99) and 5 for IgM antibodies (97,3% specificity, 95%CI 95-98). 40 out of 44 patients were positive for rRT-PCR. Among these, 39 were positive for IgG (97,5 sensibility, 95%CI 91-100); 30 were positive for IgM anti-SARS-CoV-2 (75%).
Discussion: rRT-PCR is a routine method for the diagnosis and confirmation of COVID-19 infection. However, false negative and positive results from rRT-PCR were found in a number of healthcare workers. They were possibly due to sample collection, storage conditions, difference of virus load in the infection site, RNA extraction methods and kit quality, contaminations and test performed in patients from areas with low prevalence of the infection. These rRT-PCR failures can determine an important negative impact on the diagnosis. The high sensitivity of IgG and IgM detection in the patient group indicates that serological tests are of great help in improving the clinical sensitivity of COVID-19 diagnosis. Our results show that anti-SARS-CoV-2 IgG and IgM antibody detection is a very effective tool, in association with molecular test for diagnosis, and epidemiologic studies of this severe disease.

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