Fig. 1

Study design and immunoglobulin concentrations in COVID-19 patients based on Berlin WHO classification criteria during acute phase. A The study cohort comprised 366 patients (time of admission). The patients were classified based on Berlin WHO Criteria. B Demographic and symptomatology data were recorded at the time of admission. In every group, number of patients (n), sex proportion (in percentage; %) and age range (median and 25th–75th interquartile range) are indicated in the top-right panel. C Circulating levels of IgM, IgA and IgG in ambulatory, mild, severe and critical COVID-19 patients according to the Berlin WHO pneumonia classification criteria measured by ELISA are represented by scatter dot plot with mean (wide line). Statistical differences among groups were determined by the nonparametric Kruskal–Wallis test followed by Mann–Whitney U-test. D Heatmap showing the Spearman (ρ) correlation coefficient of pairwise comparison analyses between IgM, IgA and IgG concentrations with age and selected inflammatory parameters previously related to COVID-19 disease. The correlation matrix is colour-coded according to the Spearman (ρ) correlation coefficient (− 1:1, red: blue through white), and correlations with statistical significance are indicated with an asterisk as *P < 0.05