Association of Serum Phosphorus Concentration with Mortality and Graft Failure among Kidney Transplant Recipients.
OBJECTIVE
Hyperphosphatemia in kidney transplant recipients has been shown to predict poorer graft and patient survival. However, studies examining hypophosphatemia are scarce.


METHODS
To evaluate the association of serum phosphorus level with patient and graft survival, we performed a retrospective multicenter cohort study. Between January of 1997 and August of 2012, 2786 kidney transplant recipients (41.7±11.4 years; 59.3% men; 73.5% living donors; 26.1% with diabetes; 3.8% with prior history of cardiovascular disease) were classified into seven groups according to serum phosphorus levels 1 year after transplantation, with intervals of 0.5 mg/dl (lowest group, <2.5 mg/dl; highest group, ≥5.0 mg/dl; reference group, 3.5-3.99 mg/dl). Survival analysis was performed by defining baseline time point as 1 year after transplantation.


RESULTS
During median follow-up of 78.5 months, 60 patient deaths and 194 cases of graft loss occurred. In multivariate analysis, both lowest and highest serum phosphorus groups were associated with higher mortality, compared with the reference group (hazard ratio [HR], 4.82; 95% confidence interval [95% CI], 1.36 to 17.02;P=0.01; and HR, 4.24; 95% CI, 1.07 to 16.84;P=0.04, respectively). Higher death-censored graft loss was observed in the lowest and highest groups (HR, 3.32; 95% CI, 1.42 to 7.79;P=0.01; and HR, 2.93; 95% CI, 1.32 to 6.49;P=0.01, respectively), despite eGFR exhibiting no difference between the lowest group and reference group (65.4±19.3 versus 61.9±16.7 ml/min per 1.73 m2;P=0.33). Moreover, serum phosphorus showed a U-shape association with patient mortality and graft failure in restricted cubic spline curve analysis.


CONCLUSIONS
Serum phosphorus level 1 year after transplantation exhibits a U-shape association with death-censored graft failure and patient mortality in kidney transplant patients characterized by relatively high rate of living donor transplant and low incidence of diabetes and prior cardiovascular disease compared with Western countries.
Departments of Internal Medicine and.|Department of Internal Medicine, Kangdong Sacred Heart Hospital.
Hee Jung
HJ
Jeon
Departments of Internal Medicine and.
Yong Chul
YC
Kim
Departments of Internal Medicine and.
Seokwoo
S
Park
Graduate School of Public Health, Seoul National University.
Clara Tammy
CT
Kim
Surgery, Seoul National University College of Medicine.
Jongwon
J
Ha
Department of Surgery, Asan Medical Center and University of Ulsan College of Medicine, and.
Duck Jong
DJ
Han
Department of Internal Medicine, Kangdong Sacred Heart Hospital.
Jieun
J
Oh
Departments of Internal Medicine and.
Chun Soo
CS
Lim
Surgery, Seoul National University Boramae Medical Center, Seoul, Republic of Korea.
In Mok
IM
Jung
Departments of Internal Medicine and.
Curie
C
Ahn
Departments of Internal Medicine and.
Yon Su
YS
Kim
Departments of Internal Medicine and.|Departments of Internal Medicine and.
Jung Pyo
JP
Lee
Department of Surgery, Asan Medical Center and University of Ulsan College of Medicine, and.
Young Hoon
YH
Kim
D000293:Adolescent; D000328:Adult; D000368:Aged; D002118:Calcium / Q000097:blood; D005260:Female; D005500:Follow-Up Studies; D006085:Graft Survival; D006801:Humans; D054559:Hyperphosphatemia / Q000097:blood / Q000401:mortality*; D017674:Hypophosphatemia / Q000097:blood / Q000401:mortality*; D016030:Kidney Transplantation / Q000401:mortality*; D008297:Male; D008875:Middle Aged; D010758:Phosphorus / Q000097:blood*; D012189:Retrospective Studies; D012709:Serum Albumin / Q000378:metabolism; D015996:Survival Rate; D055815:Young Adult
D012709:Serum Albumin; D010758:Phosphorus; D002118:Calcium
cardiovascular diseases; confidence intervals; diabetes mellitus; follow-up studies; glomerular filtration rate; graft survival; humans; hyperphosphatemia; hypophosphatemia; incidence; kidney; kidney transplantation; living donors; male; mortality; multivariate analysis; phosphorus; phosphorus, dietary; proportional hazards models; retrospective studies; survival analysis