Studies of the chemical composition of a butanol fraction of an extract from the above-ground part of the meadowsweet in 70% ethanol yielded five substances which were flavonoids (quercetin, isoquercetin, quercetin 4¢-glucoside, rutin) and phenolcarboxylic acids (gallic acid). The fraction was found to have nootropic actions, with antiamnestic, antihypoxic, antioxidant, and adaptogenic activities. Studies of the antioxidant properties of the individual compounds showed that isoquercetin, quercetin 4¢-glucoside, and rutin were more active than dihydroquercetin and ascorbic acid.

The frequency of AB0 and Rhesus blood groups was studied in 12120 patients with COVID-19, 5180 convalescent plasma donors and 118801 healthy donors from Moscow, Smolensk, Yakutsk, Minsk and Gomel. In infected individuals, the frequency of blood group A was significantly higher than in uninfected individuals (41,54 % and 34,39 % respectively, p<0,05), and the frequency of blood group 0, on the contrary, was significantly lower (27,69 % and 36,71 %, p<0,05). The frequency of blood group A was particularly high among patients who died from ARVI COVID-19 - 45,51 % vs. 34,39 %, p=0,008. In some groups of patients, there was a decrease in the frequency of Rh-negative individuals (2,23 % vs. 8,30 %, p<0,001).

The new coronavirus SARS-CoV-2 has become a global challenge to medicine and, in particular, laboratory diagnostics. The study of the antibodies’ level to SARS-CoV-2 can be used as a confirmation test in the diagnosis of a disease, but it becomes of paramount importance in assessing population immunity resulting from a disease or vaccination, as well as in selection of convalescent plasma donors. The kits developed in our country and abroad for detecting antibodies to the SARS-CoV-2 virus differ both in the methods of testing and in the used coronavirus antigens to which the antibodies are directed. The aim of this study was to compare the diagnostic sensitivity and specificity of five kits for the detection of IgG antibodies to the SARS-CoV-2 virus, based on different diagnostic methods. Serum samples from 137 COVID-19 convalescents and 166 donors of blood and its components were examined. The control group consisted of 50 blood sera collected at the beginning of 2019 and 19 sera collected in 2018 (before the advent of the SARS-CoV-2 virus) and stored at -70 °C. Testing was carried out in analytical systems: rapid test “COVID-19 IgM/IgG Rapid Test (Colloidal Gold)” (China), on an automatic immunochemical analyzer Abbott Architect™ i2000 and kit “SARS-CoV2-IgG” (Abbot, Chicago , IL USA), by the chemiluminescence method using an automatic analyzer of the CL series and kits of the “Mindray” company (China) “SARS-CoV-2 IgM” and “SARS-CoV-2 IgG” and by the enzyme immunoassay method on the kits of the companies “Diagnostic Systems” Ltd (Russia, Nizhny Novgorod) “DS-IFA-ANTI-SARS-CoV-2-G”, “Xema” Ltd (Federal State Budgetary Institution “National Medical Research Center of Hematology” of the Ministry of Health of Russia) “SARS-CoV-2-IgG-IFA” and “Vector-Best” CJSC (Russia, Novosibirsk)” SARS-COV-2-IgM-IFA-BEST” and “SARS-COV-2-IgG-IFABEST”. When comparing the results of testing 137 plasma samples on the Vector-Best and Mindray kits for IgG antibodies, 127 samples were positive, 7 samples were negative on both kits, the discrepancy was 2.2%. In the study of IgM antibodies, 32.1% were positive, and 52.6% were negative in both kits. The discrepancy rate was 15.3%. Out of 166 samples, 1 serum (0.6%) was negative in 5 kits. On the Mindray kit, IgG antibodies to the antigens of the SARS-CoV-2 virus were detected in 165 samples (99.4%), on Vector-Best – in 164 sera (98.8%), on Diagnostic systems – in 151 (90.96%), on Xema – in 154 (92.8%), and on Abbott – in 155 samples (93.4%). At the same time, 135 (81.33%) samples were positive in all kits, while 30 samples had discordant results (18.07%), and in 9 sera, specific IgG was not detected in 2 or more kits. ROC analysis revealed a high diagnostic value of all tested kits (AUC from 0.908 to 0.998), which indicates a high quality of the separation model of positive and negative samples (p < 0.001). With the cut-off set by the manufacturers, the sensitivity and specificity ranged from 82.8% and 93.3% for the Diagnostic Systems kit to 99.4% and 95.8% for the VectorBest kit. The calculated correlation coefficients were higher between kits with a similar composition of the antigen used in the kits; therefore, it is better to monitor the dynamics of antibodies by diagnostic kits from the same manufacturer.

This article was designed to report the results of the study based on the analysis of the statistical data related to the hepatitis b and C morbidity rates in the population of Moscow and the occurrence of the markers of these diseases among the blood donors. The study has demonstrated that the blood supply service is the source of the most reliable statistical information about the incidence and prevalence of hepatitis in the contemporary world.

Most researchers agree that the level of protective anti-HBs decreases with age after 3-fold immunization in the first year of life, which requires the introduction of a booster dose at least 5—7 years after the completed vaccination. It is necessary to continue monitoring those vaccinated against hepatitis B in the first year of life, including those from occupational risk groups.Objective: to assess the frequency and level of anti-HBs 18 or more years after the completed course of vaccination against hepatitis B according to the standard scheme in the first year of life and to identify risk groups that need revaccination.Of 116 donor students in Moscow, 18—22 years after the completed course of vaccination against hepatitis B according to the standard scheme carried out in the first year of life, in 42.3% of cases, the titer of specific antibodies was determined below the protective level (< 10 mME/ml). At the same time, the share of seronegative individuals among medical students was higher (52.8%). Of 116 donor students, in 38.8% of cases, the titer of protective antibodies was determined in low (10—100 mME/ml) and only in 13.8% — in high (100—1000 mME/ml) and in 5.2% — very high (> 1000 mME/ml) values. Markers of DNA HBV, HBsAg, and anti-HBcor were not detected in any cases. Medical students primarily need a revaccination against hepatitis B without a preliminary study of the initial titers of specific antibodies.