Mineral metabolism and haemoglobin concentration among haemodialysis patients in the Dialysis Outcomes and Practice Patterns Study (DOPPS)

Abstract

Background. Bone and mineral metabolism is abnormal in most chronic haemodialysis patients and is associated with a high mortality risk. Because of possible pathogenic links between anaemia and intact parathyroid hormone (iPTH), the present study evaluated associations of mineral metabolism indicators with haemoglobin (Hb). Methods. Data were collected from 317 facilities (12 089 haemodialysis patients) in Australia, Belgium, Canada, France, Germany, Italy, Japan, New Zealand, Spain, Sweden, the United Kingdom and the United States by the Dialysis Outcomes and Practice Patterns Study (DOPPS). The major outcome studied was probability of haemodialysis patients having a target Hb, per guidelines, of ≥11 g/dl at baseline. Major predictor variables were patient characteristics and laboratory markers of mineral metabolism: albumin-corrected serum calcium (calcium_Alb), serum phosphorus (PO₄) and iPTH. Analyses were adjusted for demographics, 15 comorbidity classes, baseline laboratory values, body mass index, years on dialysis, erythropoietin dose, vitamin D and catheter use, cause of end-stage renal disease and country. Results. The adjusted odds ratio (AOR) of having Hb ≥11 g/dl was significantly higher (PAlb (AOR = 1.32 per 1 mg/dl), higher PO₄ (AOR = 1.08 per 1 mg/dl) and lower iPTH (AOR = 0.96 per 100 pg/ml). Furthermore, 4 month intrapatient changes in Hb concentration were significantly (P9.5 mg/dl, after patient mix and Hb concentration adjustments. Conclusions. The results of this study indicate that higher serum calcium_Alb and PO₄ levels are each independently associated with better anaemia control. This relationship is independent of vitamin D use, PTH levels and prescribed rHuEpo dose. Despite this benefit of better anaemia control at higher serum calcium_Alb and PO₄ concentrations, lower calcium and PO₄ levels, as recommended by the K/DOQI guidelines, should still serve as the long-term goal for HD patients in order to minimize tissue calcification and mortality risk.