Vitamin D status in rheumatoid arthritis patients

Abstract

Recently, in the scientific world, interest in vitamin D has increased significantly, which has a healthful effect on the human body. To date, more than 30 000 scientific studies have been conducted on the study of the properties of vitamin D. It is known that rheumatoid arthritis patients (RA) often have a wide range of concomitant diseases and metabolic disorders. Current studies indicate that most RA patients have deficiency and insufficiency of vitamin D. At the same time, there is evidence that the degree of the RA activity may have a definite influence on the ability of the body to intake vitamin D. The article presents modern literary data of the vitamin D role in homeostasis, the relationship between vitamin D and the autoimmune process in RA, and the results of own studies and analysis of the prevalence of deficiency and insufficiency of vitamin D in RA patients.The objective: to assess the vitamin D status in RA patients and to study the prevalence of deficiency and insufficiency of vitamin D in RA patients.Materials and methods. We enrolled 30 RA patients, the age of 28–46 years old, 24 female and 6 male, who signed an informed consent to participate in the study. The control group was 20 people (13 female and 7 male) aged 24–44 years, without autoimmune pathology, inflammatory conditions and diseases, and signed an informed consent to participate in the study. At the time of the survey RA patients and the control group did not receive any vitamin D medications. For all patients and the control group carried out the thorough physical and laboratory examination. For evaluate vitamin D status, the M.F. Holick et al. (2011) classification was used, according to which the level of blood serum 25(OH)D is 75–375 nmol/L is considered as normal, the level of 50–75 nmol/L – as an insufficiency of vitamin D and the level below 50 nmol/L – as vitamin D deficiency. The statistical analysis was conducted on the personal computer by the Microsoft Excel and Statistica 10.0 programs. The average values (M), the standard deviation (s) and the reliability of statistical indicators (p). A p value of <0.05 was considered statistically significant.Results. 22 (73.33%) RA patients showed a decrease 25(OH)D level in serum. Vitamin D insufficiency was in 8 (26.67%) patients, 25(OH)D level in blood serum was 42.63±2.13 nmol/L. Vitamin D deficiencies in 17 (56.67%) RA patients, 25(OH)D level was 35.29±8.99 nmol/L. The normal values of vitamin D were in 8 (26.67%) RA patients, 25(OH)D level was 83.5±8.45 nmol/L. In 18 (90.00%) persons of control group the 25(OH)D was normal – 105.67±7.62 nmol/L. In 2 (10.00%) persons of control group the 25(OH)D was 69.05±3.47 nmol/L, which corresponds to vitamin D insufficiency. There was no vitamin D deficiency in the control group. The increased C-reactive protein (C-RP) was in 15 (50.00%) RA patients. The middle C-RP was 300.15 nmol/L (Min 62.9 nmol/L; Max 653.5 nmol/L). We conducted the analysis of comparing the levels of 25(OH) D with the degree of RA disease activity by DAS28-CRP. In RA patients with III degree of activity the average level of 25(OH)D was 45.00±24.16 nmol/L and was significantly lower than in RA patients with I degree of activity, whose the average level of 25(OH)D was 55.73±20.06 nmol/L (p<0.05). The average level of 25(OH)D in serum in RA patients with II degree of activity was 59.50±29.12 nmol/L. The level of serum ionized calcium in both studied groups were within the normal range and evaluate 2.38±0.27 mmol/L in RA patients and 2.43±0.18 mmol/L in the control group.Conclusions. The lowered levels of vitamin D in RA patients are found to be significantly more frequent than in the control group which equal in sex and age (p<0.001). The vitamin D insufficiency was found in 26.67% RA patients and in 10.00% control group (p<0.05). The vitamin D deficiency has been reported in 56.67% RA patients and has not been observed in the control group. There is a correlation between vitamin D deficiency and RA activity. There was a negative correlation between the vitamin D level and the degree of RA activity by the DAS28-CRP (r=–0,87; p<0,05). The vitamin D deficiency should be considered as a predictor of RA activity, which allows recommending the vitamin D medications as an additional therapy in RA patients.