Comparison of mean serum vitamin D level among inactive SLE, active SLE without lupus nephritis and active SLE with lupus nephritis

Objectives: The primary objective of this study is to compare mean serum 25OHD in SLE patients with inactive disease, SLE patients with active disease but no LN and SLE patients with active disease and LN. The secondary objective is to determine clinical predictors of vitamin D deficiency in SLE patients. Methods: This prospective study included 108 SLE patients. Patients were classified as Group(Gr) 1,2 and 3 if the patients had SLE disease activity index2K(SLEDAI) <3, ≥3 but no LN and ≥ 3 with LN. Serum 25OHD was measured by HPLC method. Results: Mean(SD) age and disease duration of patients was 35.2(11.1) and 7.9(8.3) years respectively. Mean SLEDAI in Gr1, Gr2, Gr3 was 0.7(0.9), 5.6(2.3) and 9.2(5.2) respectively. 47/108(43.5%) had vitamin D insufficiency(25OHD<30ng/ml) and 32/108(29.6%) had vitamin D deficiency(25OHD<20ng/ml). Mean 25OHD in each groups were 28.3(7.1), 26.7(9.5) and 19.9(7.6) ng/ml respectively. Patients with LN had significantly lower 25OHD than other groups (p=0.001). Serum 25OHD was significantly correlated with serum albumin(r=0.32, p=0.001), inversely correlated with SLEDAI(r=-0.30, p=0.002) and inversely correlated with UPCI(r=-0.39, p=0.001). Only UPCI was significantly inversely correlated with serum 25OHD with unstandardized coefficient -1.05(0.38) (p=0.007). Conclusion: SLE patients with LN have significantly lower vitamin D level than inactive SLE and active SLE without LN. Only UPCI is inversely correlated with 25OHD level.