Mineral metabolism and mortality in dialysis patients: a reassessment of the K/DOQI guideline.
BACKGROUND
Several studies found associations between higher plasma calcium and phosphorus and mortality in dialysis patients. However, different predefined categories and reference values were applied and the precise shape of these relationships remains unclear.


METHODS
We evaluated 1,621 patients from NECOSAD, a prospective multicenter cohort study of incident dialysis patients (60 +/- 15 years, 61% male, 64% hemodialysis). We used multivariate Cox regression and restricted cubic spline regression to study the effects of time-updated plasma concentrations on mortality in a flexible manner.


RESULTS
486 patients (30%) died during follow-up. Elevated phosphorus concentration was associated with higher mortality (p = 0.0009). The association of high calcium with mortality was borderline significant (p = 0.07). Within the studied ranges, we could not identify a threshold where an appreciable change in mortality risk occurred.


CONCLUSIONS
Mortality risk started to increase at a relatively low phosphorus concentration (4.5 mg/dl). Low-normal calcium combined with low-normal phosphorus concentration was associated with the lowest mortality.
Noordzij
Marlies
M
Departments of Clinical Epidemiology, Biostatistics, and Bioinformatics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. m.noordzij@amc.uva.nl
Korevaar
Johanna C
JC
Dekker
Friedo W
FW
Boeschoten
Elisabeth W
EW
Bos
Willem J
WJ
Krediet
Raymond T
RT
Bossuyt
Patrick M
PM
Geskus
Ronald B
RB
D000328:Adult; D000368:Aged; D001842:Bone and Bones / Q000378:metabolism; D002118:Calcium / Q000145:classification*; D002423:Cause of Death; D015897:Comorbidity; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006934:Hypercalcemia / Q000209:etiology / Q000401:mortality*; D054559:Hyperphosphatemia / Q000209:etiology / Q000401:mortality*; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000150:complications / Q000401:mortality / Q000628:therapy; D008297:Male; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D010281:Parathyroid Hormone / Q000097:blood; D010530:Peritoneal Dialysis / Q000401:mortality / Q000592:standards; D010758:Phosphorus / Q000097:blood*; D017410:Practice Guidelines as Topic; D016016:Proportional Hazards Models; D011446:Prospective Studies; D006435:Renal Dialysis / Q000401:mortality* / Q000592:standards; D012306:Risk; D012709:Serum Albumin / Q000032:analysis
D010281:Parathyroid Hormone; D012709:Serum Albumin; D010758:Phosphorus; D002118:Calcium