The aim of the study is to improve the effectiveness of antiviral treatment of patients with chronic viral hepatitis C by clinical and pathogenetic substantiation of additional use of oral cholecalciferol based on finding out the peculiarities of vitamin D metabolism disorders. A comprehensive complex clinical and laboratory examination of 100 patients with chronic viral hepatitis C at the age of 18 to 75 years and 30 healthy individuals was performed. The content of vitamin D in blood serum was determined by immunochemical with electrochemiluminescent detection method. Patients with HCV with subnormal levels of vitamin D in serum antiviral treatment was carried out and its effectiveness was assessed depending on the additional use of cholecalciferol. According to the results of studies, it was found that patients with HCV was lower in serum vitamin D content (p<0.001) than in healthy individuals, and the level of its reduction did not depend on the age and sex of patients, as well as the duration of the disease. Frequency of detection of suboptimal level of vitamin D in patients with HCV was 82,0% against 36,7% in healthy individuals (p<0.001). The content of vitamin D in serum of patients with HCV regardless of the season was lower than in healthy individuals (p<0.05), and the level of its reduction was not dependent on seasonality (ratio of chances = 1.22, confidence interval (0,38-3,90). Vitamin D deficiency and insufficiency were steadily registered in most patients both in Autumn-Winter – 78,6% and Spring-Summer – 83,5%, exceeding the corresponding indices of healthy individuals (p < 0.001). In patients with HCV, the decrease in intake of vitamin D was confirmed by the data on restriction of dietary regime due to the decrease (p<0.001) in consumption of donor products by the results of the survey. The analysis of severity of necrosis-inflammatory changes in the liver and degree of liver fibrosis in patients with HCV showed a certain dependence on serum level of vitamin D. Patients with HCV with the normal serum content of vitamin D, the severity of necrosis-inflammatory activity in the liver was higher than in patients with insufficiency and deficiency of this vitamin, which was confirmed by a more pronounced cytolysis syndrome (p=0,03) and high frequency of registration of increased activity of ALT (83,3% vs. 53,7%, p=0,02). Other indicators of the functional state of the liver do not depend on changes in the serum vitamin D content. In the presence of patients with HCV deficiency and deficiency of vitamin D in serum increased the proportion of patients with severe liver fibrosis, which was confirmed by a lower ratio of patients with stages F1-2: F3-4, compared with patients who had a normal rate of vitamin D in serum (1,2:1 vs. 2,5:1) by non-invasive tests. According to the results of the analysis of the effectiveness of additional inclusion of cholecalciferol to antiviral treatment of patients with HCV with subnormal levels of vitamin D in the serum, the feasibility of this individualization of therapy was proved.Inclusion of cholecalciferol to antiviral treatment of patients with HCV with serum vitamin D deficiency and insufficiency in the blood serum increased the probability of achieving early elimination of HCV-RNA (p<0.001) and the frequency of formation of a stable virologic response (p=0,02). Anti-viral therapy was accompanied by normalization of the content of this vitamin in the conditions of additional use of cholecalciferol. Patients who went through antiviral therapy only, had the content of this vitamin remained below normal (p<0.001) at the time of treatment completion.
