The present study aimed to assess antibody seropositivity prevalence among symptomatic individuals and individuals with a high risk of occupational exposure to SARS-CoV-2. Participants from Chelyabinsk (Russian Federation) who were at an increased risk of exposure to SARS-CoV-2 (high-risk group, n = 1091) and participants who either had symptoms consistent with COVID-19 or were suspected to have experienced COVID-19 in the past (symptomatic group, n = 692) were enrolled between 28 September and 30 December 2020. Blood samples were tested by enzyme-linked immunosorbent assay D-5501 SARS-Cov-2-IgG-EIA-BEST and D-5502 SARS-Cov-2-IgM-EIA-BEST (AO Vector-Best, Novosibirsk, Russia). The overall seropositivity rate was 28.33–28.53%. SARS-CoV-2 antibodies were detected in 17.23% (adjusted prevalence of 17.17–17.29%) of participants in the high-risk and 45.95% (adjusted prevalence of 45.91–46.24%) in the symptomatic group. Higher IgG and IgM titers were observed in women compared to men, as well as in participants in the symptomatic group compared to those in the high-risk group. The results indicate that the seroprevalence among residents in several Russian regions is low (28.38%) and inadequate to provide herd immunity. The lower seroprevalence among participants in the high-risk group may be attributed to the enforcement of healthcare protocols and the use of adequate personal protective equipment.

Aim. To identify methods for diagnosing early signs of heart failure in patients with chronic obstructive pulmonary disease. Methods. We examined 54 patients with chronic obstructive pulmonary disease without exacerbation. Patients were divided into two groups: group 1 - 26 patients with chronic obstructive pulmonary disease in combination with chronic heart failure; group 2 - 28 patients with chronic obstructive pulmonary disease without chronic heart failure. The groups were comparable by age and severity of chronic obstructive pulmonary disease. Electrocardiography, echocardiography were performed with additional determination of the right heart chamber parameters, spirometry, X-ray, pulse oximetry. The level of highly sensitive C-reactive protein, blood acid-base composition and brain natriuretic peptide was evaluated. Results. Patients with comorbidity have decreased exercise tolerance according to the 6-minute walk test and mMRS scale, higher body mass index and dyspnea intensity, larger linear dimensions of the heart chambers and their volume parameters. Heart failure with preserved ejection fraction was observed in 21 (80%) of patients in group 1, therefore, the signs of heart failure can be explained by diastolic dysfunction of the right and left ventricles. Among patients with chronic obstructive pulmonary disease and chronic heart failure in our study, extended linear dimensions and structural changes in the ventricles, indicating pre- and postcapillary hypertension, were significantly more common. Conclusion. The use of tissue Doppler study allows more accurately determining the diastolic function of the right and left ventricles; the brain natriuretic peptide study is a sensitive marker of early forms of diastolic chronic heart failure.