Background/Objectives: Vitamin D levels tend to be lower in patients with inflammatory rheumatic diseases (IRDs), including rheumatoid arthritis (RA), but there are minimal data on vitamin D levels in rheumatology patients with inflammatory vs. non-inflammatory diagnoses. Methods: In this retrospective, observational study, we used electronic health record data from patients presenting for their first visit at a large rheumatology clinic to assess vitamin D levels and deficiency based on diagnosis, and to evaluate the association between vitamin D and inflammatory markers (including C-reactive protein CRP) or autoimmune markers (including rheumatoid factor RF, anti-citrullinated peptide antibody, and anti-nuclear antibodies). Logistic regression analysis with 13 clinical variables was used to evaluate the association between vitamin D levels and IRD diagnosis, and linear regression was used to evaluate the association between vitamin D levels and CRP or RF. Results: The patient cohort included 4979 patients; 1385 (27.8%) had an IRD. Vitamin D levels were significantly lower in the IRD vs. non-inflammatory subgroup (mean SD of 26.6 13.3 vs. 27.7 14.3; p = 0.009), but the difference was not clinically relevant given the small effect size. Vitamin D deficiency rates (<20 ng/mL) were not significantly different between the subgroups, and vitamin D was not associated with an IRD diagnosis in logistic regression analysis. In linear regression analysis, vitamin D was not associated with CRP or RF in the full patient cohort or in the subgroup with RA (n = 539). Conclusions: We conclude that vitamin D levels do not differ substantially based on IRD versus non-inflammatory diagnosis, CRP levels, or RF levels in this clinical cohort.
Schäfer et al. (Tue,) studied this question.