Vitamin D may not be a good marker of disease activity in Korean patients with systemic lupus erythematosus

Abstract

Vitamin D is a pleiotrophic hormone with immunoregulatory properties. Low levels of vitamin D have been discovered in various autoimmune diseases. Here, we investigated serum vitamin D levels in Koreans with systemic lupus erythematosus (SLE) and examined whether levels correlate with disease activity of SLE. Blood samples were prospectively collected from patients with SLE (n = 104) and normal controls (NC, n = 49) during the spring from March to May 2008. The level of serum 25-hydroxyvitamin D (25(OH)D3) was measured by radioimmunoassay. The serum 25(OH)D3 levels of patients with SLE (42.49 ± 15.08 ng/ml) were significantly lower than NC (52.72 ± 15.19 ng/ml, P \ 0.001). Additionally, 17 patients with SLE (16.3%) had vitamin D insufficiency, while two NC had vitamin D insufficiency (4.1%). The risk of vitamin D insufficiency was 4.6-fold increased in SLE (P = 0.032). The serum 25(OH)D3 levels, adjusted with BMI, were positively correlated only with hemoglobin (b = 0.256, P = 0.018) and serum complement 3 (b = 0.365, P = 0.002). Serum vitamin D levels were lower, and vitamin D insufficiency was more common in Korean patients with SLE, however, our study demonstrated that vitamin D levels might not be a good marker of disease activity.

An evaluation of vitamin D status in individuals with systemic lupus erythematosus

“…To improve the validity of a study, it is necessary to select an appropriate control group when making comparisons. Studies that have shown vitamin D status is significantly lower in SLE have all selected free living and apparently healthy control groups (12,(17)(18)(19)(20)(21) making their findings more robust.…”

“…The majority of studies conducted to date have reported significantly lower vitamin D status in individuals with SLE compared to controls (12,(17)(18)(19)(20)(21) ; however, some studies have indicated no significant difference in serum 25(OH)D concentrations between SLE patients and controls (33)(34)(35) ( Table 1). Taking into consideration the line of latitude that the study was conducted does not appear to explain the variations of vitamin D status of those with SLE ( Table 1) and suggests that other factors are impacting on status in this group.…”

“…Two studies involving Asian cohorts utilised >75 nmol/l to represent vitamin D sufficiency and <50 nmol/l as vitamin D deficiency (19,20) . Damanhouri (20) based cut-offs for sufficient vitamin D status (75 nmol/l) in Saudi SLE patients based on a review by Holick (38) .…”

“…The results showed an improvement in levels of fatigue, albeit, they did not identify an improvement in overall disease activity (16) . Over the past 15 years, and in particular in the last 5 years, research has reported that SLE patients have significantly lower vitamin D status than their healthy counterparts (12,(17)(18)(19)(20)(21) . Some have reported an association between vitamin D status and disease activity with lower vitamin D status contributing to greater disease activity (17)(18)(19)(20)(22)(23)(24)(25) .…”

“…Over the past 15 years, and in particular in the last 5 years, research has reported that SLE patients have significantly lower vitamin D status than their healthy counterparts (12,(17)(18)(19)(20)(21) . Some have reported an association between vitamin D status and disease activity with lower vitamin D status contributing to greater disease activity (17)(18)(19)(20)(22)(23)(24)(25) . An association between vitamin D and fatigue has also been reported (16,26) ; however, not all studies have observed a relationship between vitamin D and indices of disease activity in SLE (27)(28)(29)(30) .…”