Predictors and consequences of altered mineral metabolism: the Dialysis Outcomes and Practice Patterns Study.
BACKGROUND
Altered mineral metabolism contributes to bone disease, cardiovascular disease, and other clinical problems in patients with end-stage renal disease.


METHODS
This study describes the recent status, significant predictors, and potential consequences of abnormal mineral metabolism in representative groups of hemodialysis facilities (N= 307) and patients (N= 17,236) participating in the Dialysis Outcomes and Practice Patterns Study (DOPPS) in the United States, Europe, and Japan from 1996 to 2001.


RESULTS
Many patients fell out of the recommended guideline range for serum concentrations of phosphorus (8% of patients below lower target range, 52% of patients above upper target range), albumin-corrected calcium (9% below, 50% above), calcium-phosphorus product (44% above), and intact PTH (51% below, 27% above). All-cause mortality was significantly and independently associated with serum concentrations of phosphorus (RR 1.04 per 1 mg/dL, P= 0.0003), calcium (RR 1.10 per 1 mg/dL, P < 0.0001), calcium-phosphorus product (RR 1.02 per 5 mg(2)/dL(2), P= 0.0001), PTH (1.01 per 100 pg/dL, P= 0.04), and dialysate calcium (RR 1.13 per 1 mEq/L, P= 0.01). Cardiovascular mortality was significantly associated with the serum concentrations of phosphorus (RR 1.09, P < 0.0001), calcium (RR 1.14, P < 0.0001), calcium-phosphorus product (RR 1.05, P < 0.0001), and PTH (RR 1.02, P= 0.03). The adjusted rate of parathyroidectomy varied 4-fold across the DOPPS countries, and was significantly associated with baseline concentrations of phosphorus (RR 1.17, P < 0.0001), calcium (RR 1.58, P < 0.0001), calcium-phosphorus product (RR 1.11, P < 0.0001), PTH (RR 1.07, P < 0.0001), and dialysate calcium concentration (RR 0.57, P= 0.03). Overall, 52% of patients received some form of vitamin D therapy, with parenteral forms almost exclusively restricted to the United States. Vitamin D was potentially underused in up to 34% of patients with high PTH, and overused in up to 46% of patients with low PTH. Phosphorus binders (mostly calcium salts during the study period) were used by 81% of patients, with potential overuse in up to 77% patients with low serum phosphorus concentration, and potential underuse in up to 18% of patients with a high serum phosphorus concentration.


CONCLUSIONS
This study expands our understanding of the relationship between altered mineral metabolism and outcomes and identifies several potential opportunities for improved practice in this area.
Young
Eric W
EW
Department of Veterans Affairs Medical Center, and Division of Nephrology, University of Michigan, Ann Arbor, Michigan, USA. DOPPS@urrea.org
Albert
Justin M
JM
Satayathum
Sudtida
S
Goodkin
David A
DA
Pisoni
Ronald L
RL
Akiba
Takashi
T
Akizawa
Tadao
T
Kurokawa
Kiyoshi
K
Bommer
Jürgen
J
Piera
Luis
L
Port
Friedrich K
FK
D002118:Calcium / Q000097:blood*; D015314:Dialysis Solutions / Q000737:chemistry; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood; D016105:Parathyroidectomy; D010758:Phosphorus / Q000097:blood*; D010818:Practice Patterns, Physicians'; D006435:Renal Dialysis; D014807:Vitamin D / Q000627:therapeutic use
D015314:Dialysis Solutions; D010281:Parathyroid Hormone; D014807:Vitamin D; D010758:Phosphorus; D002118:Calcium