A prospective, randomized, controlled multicenter trial to evaluate 1.25 mmol/L (physiological) vs. 1.5 mmol/L calcium dialysate on serum markers of mineral metabolism, secondary hyperparathyroidism and cardiovascular calcification in prevalent haemodialysis patients. And the long term safety of the 1.25 mmol/L calcium dialysate was also considered.

There are two phases of study for each subject. Phase 1 (screening phase). During this phase, each potential subject will be evaluated to determine if he/she is eligible for the study.

Phase 2 (intervention phase). Each subject will be randomly allocated to physiological calcium dialysate (1.25 mmol/L calcium dialysate) group (PCD group), and normal calcium dialysate (1.5 mmol/L calcium dialysate) group (NCD group). The follow-up duration was 36 months.

All patients recruited from these centers who met the inclusion criteria were randomly allocated to physiological calcium dialysate (1.25 mmol/L calcium dialysate) group (PCD group), and normal calcium dialysate (1.5 mmol/L calcium dialysate) group (NCD group). The follow-up duration was 36 months.

Calcium carbonate was mainly used as the phosphate binder. Active vitamin D metabolite, calcitriol (Rocaltrol, Hoffmann La Roche, and Basel, Switzerland) was given as to control the secondary hyperparathyroidism. The doses of these agents were adjusted according to the serum calcium level, serum phosphate level, calcium-phosphorus product and serum iPTH level, which were recommended by the K/DOQI Guidelines 6.3b and 8B. Aluminum hydroxide might be introduced as a phosphate binder for no more than 4 weeks in addition to calcium carbonate and dietary restriction when serum phosphate level could not get a good control (serum P level≥1.78 mmol/L, lasting above 4 weeks). A non- calcium-containing phosphate binder could be administered for 1~2 weeks in patients with hypercalcaemia during the observation. At the time of the study, non-calcium, non-aluminum based phosphate binders as well as calcium acetate were not available in our country.

Inclusion Criteria:

• Willingness to sign an informed consent
• Stable haemodialysis treatment for more than 3 months, undergoing 2 to 3 times haemodialysis a week for 4 to 5 hours per session
• Secondary hyperparathyroidism defined as serum intact parathyroid hormone (iPTH) > 150 pg/mL, hypercalcemia defined as serum Ca > 2.2 mmol/L and /or calcium phosphate product ≥55mg2/dl2

Exclusion Criteria:

• Inability or unwillingness to sign the informed consent
• Cardiac arrhythmia
• Serious renal osteopathy
• Oral active vitamin D and/or calcium carbonate intolerance
• Poor compliance or unwillingness to meet the scheme demands raised by the investigators
• Patients who had undergone percutaneous ethanol injection therapy or parathyroidectomy for secondary hyperparathyroidism
• Patients who had previously been treated and/or were being treated with glucocorticoid, which affects bone metabolism.