Immune response and laboratory markers in the spectrum of severity of COVID-19

In this retrospective cohort study, we examined the possible relationship between disease severity, laboratory markers of inflammation, and the development of antibodies to SARS-Cov-2 in patients with acute COVID-19 during the 1st week of hospitalization. In 47% of hospitalized patients with COVID-19, 19 during the first week of hospital stay, IgM and IgG antibodies to SARS-CoV-2 were detected, both in the case of a positive and negative PCR test. An average positive correlation of detected IgM and IgG with antibodies to the receptor-binding site (RBD) of the S protein of the SARS-Cov-2 virus is shown. In total, IgM and IgG antibodies to SARS-Cov-2 were most often detected in patients with a favorable course of the disease. Laboratory parameters in patients with moderate and severe COVID-19 were characterized by a significant increase in the level of serum C-reactive protein (CRP), an increase in the neutrophil-leukocyte ratio (NLR) and fibrinogen level, in comparison with data from patients with a mild course of the disease. In mild cases of infection, a moderately negative correlation was revealed between the levels of antibodies to SARS-Cov-2 and NLR.

Thus, detection of antibodies to SARS-CoV-2 in the early stages of hospitalization may be a predictor of a favorable outcome of the disease and serve as an additional criterion for the diagnosis of COVID-19 along with PCR analysis.