Vitamin D Status in Rheumatology Patients with Inflammatory Compared with Non-Inflammatory Diagnoses: Inflammatory and Autoimmune Markers Are Not Associated with Vitamin D Levels

TL;DR

This study found no strong link between vitamin D levels and inflammatory or autoimmune markers in rheumatology patients.

Contribution

The study compares vitamin D levels in patients with inflammatory versus non-inflammatory rheumatic diagnoses and finds no significant clinical association.

Findings

Vitamin D levels were slightly lower in inflammatory rheumatic disease patients but not clinically significant.

Vitamin D deficiency rates were similar between inflammatory and non-inflammatory subgroups.

No association was found between vitamin D levels and inflammatory or autoimmune markers like CRP or RF.

Abstract

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.

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