Vitamin D status of patients with early inflammatory arthritis

The present study aimed to investigate the vitamin D status in patients with early inflammatory arthritis (EIA). We conducted a retrospective study among patients who presented with EIA at the outpatient rheumatology clinic of a tertiary referral center between March 2012 and February 2013. In total, 101 subjects with EIA (≥1 swollen joint and symptom duration of ≤6 months, not explained by another disease) and 101 healthy controls matched for age, sex, and the month of serum vitamin D measurements were enrolled. Serum 25-hydroxy vitamin D (25-OHD) concentrations were assessed by radioimmunoassay. Vitamin D "deficiency" and "severe deficiency" were defined as serum 25-OHD levels <20 and <10 ng/mL, respectively. Among EIA patients, rheumatoid arthritis (RA) was classified according to the 2010 American College of Rheumatology/European League against Rheumatism criteria. Vitamin D deficiency was highly prevalent among EIA patients, but no significant differences in the frequency of vitamin D deficiency of EIA patients and controls were observed (75.2 vs 65.3%, p = 0.106). Additionally, in spring and summer, EIA patients had significantly lower serum 25-OHD concentrations than controls, but the opposite trend was observed in autumn. Among 101 EIA patients, 38 (37.1%) were classified as having RA. Severe vitamin D deficiency in EIA patients was significantly associated with the higher likelihood of being classified as having RA. In conclusion, the frequency of vitamin D deficiency in EIA patients was comparable to that in controls, but severe vitamin D deficiency was associated with the presence of RA among EIA patients.