AB0476 VITAMIN D SERUM CONCENTRATION VARIES ACCORDING TO DISEASE ACTIVITY IN SPONDYLOARTHRITIS

Abstract

Background:Several studies have shown dissimilar results for the relationship between serum 25-hydroxyvitamin D concentration (25-OH-D) and disease activity in spondyloarthritis (SpA).Objectives:This study aims to assess whether vitamin D levels vary according to disease activity in patients with SpA before and after starting treatment with biologic disease-modifying anti-rheumatic drugs (bDMARDs).Methods:An observational retrospective study was performed in SpA patients followed in the Rheumatology department of a tertiary university hospital. Demographic and clinical data were collected from the Rheumatic Diseases Portuguese Register (Reuma.pt). Patients were assessed for 25-OH-D levels before and after 6 months of treatment with the first bDMARD. Correlation between 25-OH-D levels and disease activity measured by Ankylosing Spondylitis Disease Activity Score (ASDAS) at baseline and after 6 months were assessed using student’s t-test for two samples and one-way ANOVA and with post hoc tests for multiple comparisons.Results:A total of 189 patients were included. Ninety-seven patients were females (51.3%). The mean age at diagnosis was 34.8±11.2 years and the median disease duration at the start of the first bDMARD was 4.9 years (min: 0.1; max: 46.0). All patients fulfilled the ASAS criteria for SpA. Nonsteroidal anti-inflammatory drugs were used by 102 patients (54.0%) and conventional synthetic DMARDs by 69 patients (36.5%). At 6 months, 188 patients were treated with tumor necrosis factor inhibitors and one with interleukin-17 inhibitor. According to ASDAS criteria, at baseline 36.8% of patients had high disease activity and 59.5% had very high disease activity. After 6 months of treatment with bDMARD 14.7% of patients have inactive disease, 21.6% low disease activity, 36.3% high activity and 12.6% very high disease activity. The mean value of 25-OH-D at baseline was significantly lower in the group of patients with very high disease activity compared to the patients with high disease activity (21.9±11.1 ng/ml vs 26.1±11.6 ng/ml, p= 0.02). At 6 months of treatment the mean value of 25-OH-D in inactive, low, high and very high disease activity was 31.0±17.1ng/ml, 28.5±11.2ng/ml, 25.8±10.8ng/ml and 19.3 ±9.5ng/ml, respectively. There was a statistically significant difference between the groups, as determined by one-way ANOVA (p = 0.001). A post hoc Dunnett T3 test revealed that patients with very high disease activity have significantly lower mean 25-OH-D levels (19.29 ± 9.5) than patients with inactive disease (31.0 ± 17.1, p = 0.025) and low activity (28.5 ± 11.2, p = 0.009). Among the groups with high and very high disease activity, the significance is only marginal (p = 0.068).Conclusion:Vitamin D serum concentration varies according to disease activity in SpA. In fact, SpA patients with lower levels of 25-OH-D are associated with higher rates of disease activity, even in patients treated with biologics agents. It is important to be aware of vitamin D level as it can play a role in the management and treatment of the disease, mainly in the most severe patients.