Elevated serum phosphate predicts mortality in renal transplant recipients.
BACKGROUND
High serum phosphate has been identified as an important contributor to the vascular calcification seen in patients with chronic kidney disease (Block et al., Am J Kidney Dis 1998; 31: 607). In patients on hemodialysis, elevated serum phosphate levels are an independent predictor of mortality (Block et al., Am J Kidney Dis 1998; 31: 607; Block, Curr Opin Nephrol Hypertens 2001; 10: 741). The aim of this study was to investigate whether an elevated serum phosphate level was an independent predictor of mortality in patients with a renal transplant.


METHODS
Three hundred seventy-nine asymptomatic renal transplant recipients were recruited between June 2000 and December 2002. Serum phosphate was measured at baseline and prospective follow-up data were collected at a median of 2441 days after enrolment.


RESULTS
Serum phosphate was significantly higher in those renal transplant recipients who died at follow-up when compared with those who were still alive at follow-up (P<0.001). In Kaplan-Meier analysis, serum phosphate concentration was a significant predictor of mortality (P=0.0001). In multivariate Cox regression analysis, serum phosphate concentration remained a statistically significant predictor of all-cause mortality after adjustment for traditional cardiovascular risk factors, estimated glomerular filtration rate, and high sensitivity C reactive protein (P=0.036) and after adjustment for renal graft failure (P=0.001).


CONCLUSIONS
The results of this prospective study are the first to show that a higher serum phosphate is a predictor of mortality in patients with a renal transplant and suggest that serum phosphate provides additional, independent, prognostic information to that provided by traditional risk factors in the risk assessment of patients with a renal transplant.
Department of Clinical Biochemistry, Royal Victoria Hospital, Belfast, Northern Ireland. grainnemconnolly@aol.co.uk
Grainne M
GM
Connolly
Ronan
R
Cunningham
Peter T
PT
McNamee
Ian S
IS
Young
Alexander P
AP
Maxwell
D000328:Adult; D015415:Biomarkers / Q000097:blood; D001794:Blood Pressure; D002097:C-Reactive Protein / Q000378:metabolism; D002118:Calcium / Q000097:blood; D005500:Follow-Up Studies; D005919:Glomerular Filtration Rate; D006801:Humans; D054559:Hyperphosphatemia / Q000175:diagnosis; D016030:Kidney Transplantation / Q000401:mortality / Q000502:physiology*; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood; D010710:Phosphates / Q000097:blood*; D011237:Predictive Value of Tests; D011379:Prognosis; D012189:Retrospective Studies; D016019:Survival Analysis; D017741:Survivors
D015415:Biomarkers; D010281:Parathyroid Hormone; D010710:Phosphates; D002097:C-Reactive Protein; D002118:Calcium