Detection of vitamin D in sera of patients with atopic dermatitis and its clinical significance

Objective To measure the serum levels of vitamin D, total immunoglobulin E (tIgE) , interleukin-4 (IL-4) and IL-6 in patients with atopic dermatitis (AD) , to evaluate the association between vitamin D and severity of AD, and to investigate the role of vitamin D in inflammatory and immunoregulatory processes during the occurrence of AD. Methods Peripheral blood samples were collected from 37 patients with AD (AD group) and 30 healthy controls (control group) . The serum levels of vitamin D, tIgE, and IL-6 were measured by chemiluminescent sandwich enzyme immunoassay, and those of IL-4 by enzymelinked immunosorbent assay. The severity of AD was assessed by the SCORing atopic dermatitis (SCORAD) score. The t test or Mann-Whitney U test was performed to assess the differences in vitamin D, tIgE, IL-4 and IL-6 levels between the AD group and control group, chisquare test to compare the proportion of patients with vitamin D deficiency, insufficiency and sufficiency, and Pearson′s correlation analysis or Spearman′s correlation analysis to evaluate the correlations between the SCORAD score and serum levels of vitamin D, tIgE, IL-4 and IL-6. Results Compared with the control group, the AD group showed significantly decreased serum levels of vitamin D (24.77 ± 9.29 vs. 28.98 ± 6.87 μg/L, t= 2.015, P= 0.048) , but significantly increased serum levels of tIgE (137.68 [37.59-414.53] vs. 45.16 [14.56-112.12] IU/ml, Z=-3.399, P= 0.001) , IL-4 (8.86 ± 4.83 vs. 4.78 ± 3.07 ng/L, t= 4.147, P < 0.001) and IL-6 (6.53[3.99-15.30] vs. 4.58[2.85-8.17] ng/L, Z=-2.173, P= 0.030) . Among patients with AD, the SCORAD score was negatively correlated with serum levels of vitamin D (r=-0.505, P= 0.001) , positively correlated with those of tIgE (r= 0.531, P= 0.001) and IL-4 (r= 0.519, P= 0.001) , but uncorrelated with those of IL-6 (r=-0.139, P= 0.411) . There were significant differences in the proportion of patients with vitamin D deficiency, insufficiency and sufficiency between the AD group and control group (χ2= 8.762, P= 0.013) . AD patients with vitamin D deficiency showed significantly increased serum levels of tIgE (2846.87 [319.02-7300.00]IU/ml) and IL-4 ([16.37 ± 2.05]ng/L) compared with those with vitamin D insufficiency (110.07[26.20-501.48] IU/ml, P= 0.045; [8.28 ± 4.48] ng/L, P= 0.011) and those with vitamin D sufficiency (123.93 [91.61-273.68] IU/ml, P= 0.024; [8.00 ± 4.63] ng/L, P = 0.041) . In addition, serum levels of IL-6 were also higher in patients with vitamin D deficiency than in those with vitamin D sufficiency (15.10 [8.49-30.72] vs. 6.22 [4.47-9.47] ng/L, P= 0.011]. Conclusions Vitamin D deficiency or insufficiency exists in patients with AD. Vitamin D deficiency is correlated with high serum levels of tIgE, IL-4 and IL-6, and the severity of AD is closely correlated with increased serum levels of tIgE and IL-6 as well as decreased serum levels of vitamin D. Key words: Dermatitis, atopic; Vitamin D; Immunoglobulin E; Interleukin-4; Interleukin-6; Severity of illness index