Association of Pretransplant Serum Phosphorus with Posttransplant Outcomes

Abstract

Serum phosphorus levels are associated with mortality, cardiovascular disease, and renal function loss in individuals with and without chronic kidney disease. The association of pretransplant serum phosphorus levels with transplant outcomes is not clear. Data of the Scientific Registry of Transplant Recipients (SRTR) up to June 2007 were linked to the database (2001 through 2006) of one of the U.S.-based large dialysis organizations (DaVita). The selected 9384 primary kidney recipients were divided into five groups according to pretransplant serum phosphorus levels (mg/dl): <3.5, 3.5 to <5.5 (reference group), 5.5 to <7.5, 7.5 to <9.5, and ≥9.5. Unadjusted and multivariate adjusted risks for transplant outcomes were compared. Patients were 48 ± 14 years old and included 37% women and 27% African Americans. After multivariate adjustment, all-cause and cardiovascular death hazard ratios were 2.44 (95% confidence interval: 1.28 to 4.65) and 3.63 (1.13 to 11.64), respectively, in recipients in the ≥9.5 group; allograft loss hazard ratios were 1.42 (1.04 to 1.95) and 2.36 (1.33 to 4.17) in recipients with 7.5 to >9.5 and ≥9.5, respectively. No significant association with delayed graft function was found. Pretransplant phosphorus levels 7.5 to <9.5 mg/dl and ≥9.5 mg/dl were associated with increased risk of functional graft failure and increased risk of all-cause and cardiovascular deaths, respectively, when compared with 3.5 to <5.5 mg/dl. Additional studies are needed to examine whether more aggressive control of pretransplant serum phosphorus may improve posttransplant outcomes.