Objectives To study the relationship between serum 25-hydroxyvitamin D3 levels and flares of systemic lupus erythematosus (SLE) in a longitudinal cohort of Chinese patients.
Methods Patients who fulfilled ≥4 of the ACR criteria for SLE were recruited from our rheumatology out-patient clinics in November 2011. Blood was taken at 10 AM and was assayed for the serum levels of 25-hydroxyvitamin D3 by liquid chromatography tandem mass spectrometry (LC-MS/MS). Patients were stratified according to the 25-hydroxyvitamin D3 levels; group 1 (<15ng/ml, deficiency); group 2 (15–30ng/ml, insufficiency); and group 3 (>30ng/ml, adequate); and were followed longitudinally every 2–4 months for serial assessment of disease activity (by SELENA-SLEDAI) and the occurrence of mild/moderate or severe SLE flares (by SELENA flare instrument). Comparison was made among these groups in the baseline and mean summated SLEDAI over time (area under the curve), and the annual incidence of mild/moderate and severe flares by the one-way ANOVA test.
Results 276 SLE patients were studied (94% women; age 41.0±13.8 years; SLE duration 8.7±6.6 years). 25 (9.1%) patients had eGFR ≤60ml/min. The proportion of patients with 25-hydroxyvitamin D3 levels of <15, 15–30, >30ng/ml was 26%, 54% and 20%, respectively. Patients with vitamin D deficiency (group 1) were significantly younger, had lower body mass index (BMI) but higher baseline eGFR and SLEDAI scores when compared with the other groups. No significant differences in the clinical manifestations were observed among the three groups of patients except for lower prevalence of facial rash in group 3 (p=0.02). After a mean follow-up of 32.5±5.5 months, 153 mild flares and 91 severe flares developed in our patients. The mean summated SLEDAI score over time was: 3.2±2.0 (group 1); 2.4±1.9 (group 2); and 2.7±2.1 (group 3), respectively (p=0.02). The annual incidence of mild/moderate and severe flares was: 0.26±0.39 and 0.20±0.45 (group 1); 0.20±0.33 and 0.09±0.22 (group 2); and 0.20±0.32 and 0.14±0.46 (group 3), respectively (p=NS in all). In a subgroup of 73 patients who did not have clinical or serological SLE activity at baseline (SLEDAI=0), a similar but non-significant trend of higher annual rates of mild/moderate and severe flares over time was also observed in patients with vitamin D deficiency. At the last visit, 27 (10%) patients had new damage scores; 5 patients had new vascular events; and 4 patients had new onset diabetes mellitus. There were no significant differences among the three groups of patients with regard to the incidence of new damage or vascular events over time.
Conclusions Vitamin D insufficiency and deficiency was frequent in our cohort of SLE patients. Patients with vitamin D deficiency were associated with higher baseline and mean disease activity scores, as well as a tendency of more severe lupus flares over time.
Disclosure of Interest None declared