Association of time-updated plasma calcium and phosphate with graft and patient outcomes after kidney transplantation

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Abstract

Disturbances in calcium-phosphate homeostasis are common after kidney transplantation. We aimed to assess the relationship between deregulations in plasma calcium and phosphate over time and mortality and death-censored graft failure (DCGF). In this prospective cohort study we included kidney transplant recipients with ≥2 plasma calcium and phosphate measurements. Data were analyzed using time-updated Cox regression analyses adjusted for potential confounders including time-updated kidney function. We included 2,769 patients (mean age 47±14 years, 42.3% female) with 138,496 plasma calcium and phosphate levels (median [IQR] 43 [31-61] measurements per patient). During follow-up of 16.3 [8.7-25.2] years, 17.2% developed DCGF and 7.9% died. Post-transplant hypercalcemia was associated with an increased risk of mortality (1.63 [1.31-2.00], P<0.0001), but not DCGF. Hyperphosphatemia was associated with both DCGF (2.59 [2.05-3.27], P<0.0001) and mortality (3.14 [2.58-3.82], P<0.0001). Only the association between hypercalcemia and mortality remained significant in sensitivity analyses censored by a simultaneous eGFR <45 mL/min/1.73 m2 . Hypocalcemia and hypophosphatemia were not consistently associated with either outcome. Post-transplant hypercalcemia, even in the presence of preserved kidney function, was associated with an increased mortality risk. Associations of hyperphosphatemia with DCGF and mortality may be driven by eGFR.

Original languageEnglish
Pages (from-to)2437-2447
Number of pages11
JournalAmerican Journal of Transplantation
Volume21
Issue number7
Early online date17-Dec-2020
DOIs
Publication statusPublished - Jul-2021

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