To explore the expression and significance of vitamin D (VitD) in patients with rheumatoid arthritis (RA), and analyze the relationship between its expression and clinical indicators.

Clin-ical parameters and laboratory examinations of RA cases (n=250) were collected. Clinical parameters included were gender, age, disease course, swollen joints number, tenderness joints number, visual analog pain score (VAS), disease activity score (DAS)28 score. Laboratory examinations included erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), rheumatoid factor (RF) and anti-cyclic citrullinated peptide (CCP) antibody, antinuclear (ANA) antibody, antikeratin (AKA) antibody, anti-perinuclear factor (APF), anti-mutated citrullinated vimentin (MCV), antibody and anti-6-glucose phosphate isomerase (GPI) antibody, lymphocyte subsets in the peripheral blood and lymphocyte subsets of CD4⁺ T cells. The level of 25-(OH)-Vit-D and clinical parameters, laboratory examinations were analyzed retrospectively. One-way ANOVA and Kruskal-Wallis test were used for comparison among the groups, and the correlation analysis was performed by Pearson and Spearman rank correlation analysis.

① The level of 25-(OH) D in RA patients was significantly lower than that in healthy controls(t=11.676, P<0.01). ② According to 25-(OH)D level, RA patients were divided into the deficiency group, insufficient group and normal group, the tender joints count (χ²=17.793, P<0.001), the number of swollen joints (χ²=12.635, P=0.002), ESR (F=6.330, P=0.002), VAS score (F=5.095, P=0.007, DAS28 (F=4.990, P=0.008) were different significantly among the three groups. ③ RF (χ²=6.742, P=0.034) and anti-CCP antibody (χ²=6.836, P=0.033) were different significantly among the three groups and the level of 25-(OH) D was negatively correlated with RF (r=-0.202, P=0.001), anti-CCP antibody (r=-0.220, P<0.01), anti-MCV antibody (r=-0.109, P=0.002) and AKA (r=-0.215, P=0.001). ④ The level of 25-(OH) D in the RF (t=-2.715, P=0.007) , anti-CCP antibody (t=-2.03, P=0.044), AKA (t=-2.108, P=0.036) negative group was significantly higher than that in patients with antibody positive group. ⑤ The level of Th1 (IFN-γ) cells (F=3.259, P=0.043) and Treg (CD4⁺ CD25⁺ Foxp3⁺) cells (F=4.342, P=0.031) were significantly different among the three groups and the level of 25-(OH) D was positively correlated with Treg (CD4⁺ CD25⁺ Foxp3⁺) cells (r=0.146, P=0.025).

Vitamin D is generally deficient in RA patients, which is significantly correlated with disease activity, RF, anti-CCP antibody, anti-MCV antibody, AKA and Th1, Treg cells. It is suggested that vitamin D may play an important role in the immunological pathogenesis and disease progression of RA.

Arthritis, rheumatoid; 25-Hydroxy-vitamin D; Autoantibodies; Immunocompetence