Abstract: 【Abstract】 Objective To examine the prevalence of 25-hydroxyvitamin D (25(OH)D) deficiency and insufficiency in CKD patients at stage 5 and on maintenance peritoneal dialysis (PD) and to evaluate the factors relating to serum 25(OH)D level, so as to provide useful bases for appropriate therapy. Methods We recruited 101 maintenance PD patients with stable status and to be regularly followed up for at least three months at the Department of Nephrology, Peking University People’s Hospital from December 2010 to February (winter) 2011. Serum 25(OH)D level was measured by ELISA. Patients’ general data were recorded. Serum 25(OH)D level and the parameters of mineral metabolism (serum albumin corrected calcium, phosphorus, intact parathyroid hormone and bone-specific alkaline phosphatase), nutritional index (serum albumin and body mass index), hemoglobin, serum creatinine, residual renal function, total urea clearance (Kt/V), and total creatinine clearance were determined. Multiple linear regression analysis was used to assess the factors relating to serum 25(OH)D level. Results A total of 101 PD patients (49 males and 52 females with a mean age of 61.8±14.1 years) were enrolled in this study. Their average PD duration was 25.9±21.7 months. Their major primary disease was diabetic nephropathy, accounting for 40.6% of the patients. Their average serum 25(OH)D was 9.92±2.44ng/ml (5.6-17.83ng/ml). Vitamin D insufficiency was found in 3.96% (4/101) patients, and vitamin D deficiency in 96.04% (97/101) patients. Serum 25(OH)D were significantly lower in PD patients with diabetes than in those without diabetes (P＜0.05). Multiple linear regression analysis demonstrated that outdoor activities (β= 0.223, P= 0.026), serum albumin corrected calcium level (β= 0.203, P=0.048) and residual renal function (β=0.267, P=0.012) were the independent factors relating to 25(OH)D level. Conclusions Vitamin D deficiency/insufficiency is frequently found in CKD patients at stage 5 undergoing PD in winter in northern China. Hypocalcemia, loss of residual renal function, and less outdoor activities are the independent risk factors relating to vitamin D deficiency/insufficiency. Vitamin D supplement of appropriate dose should be given as early as possible o these patients.

Key words: Peritoneal dialysis, 25-hydroxyvitamin D, Vitamin D, Residual renal function