Serum Phosphorus and Risk of Graft Failure or Mortality in Transplant Recipients

Orlando—Recipients of kidney transplants may be at risk for mild hyperphosphatemia, a putative risk factor for cardiovascular disease (CVD), loss of renal function, and mortality. There are few data available from large, multicenter cohorts of stable kidney transplant recipients that assess the relationships between serum phosphorus and the development of CVC outcomes, graft failure, or all-cause death.

Basma Merhi, MD, and colleagues conducted a study to examine the association of serum phosphorus level and CVD adverse outcomes, graft failure, or mortality in a cohort of participants of the FAVORIT (Folic Acid for Vascular Outcome Reduction in Transplantation) trial. They reported results of the analysis during a poster session at the NKF 2017 Spring Clinical Meetings in a poster titled Serum Phosphorus and Risk of Cardiovascular Disease, Graft Failure, or All-Cause Mortality in Chronic Kidney Transplant Recipients.

Of the participants in FAVORIT, 3181 had serum phosphorous level data available at randomization: mean phosphorus level was 3.07 mg/dL (range, 0.79-8.32 mg/dL). Among that cohort, there were 445 cardiovascular outcomes, 351 deaths, and 242 graft failures during a median follow-up of 4.0 years.

The researchers conducted a proportional hazards model, adjusting for age, baseline CVD, diabetes, smoking status, race, sec, body mass index, low-density cholesterol, high-density cholesterol, triglycerides, estimated glomerular filtration rate (eGFR), urinary albumin/creatinine (UA/Cr), type of kidney graft, graft vintage, and the use of calcineurin inhibitors, steroids, or lipid lowering drugs. There was no association between each 1 mg/dL higher serum potassium level and a significant increase in cardiovascular risk (hazard ratio [HR], 1.06; 95% confidence interval [CI], 0.92-1.22). There was a significant association between each 1 mg/dL higher serum potassium level and increased risk of graft failure (HR, 1.38; 95% CI, 1.16-1,64) and total mortality (HR, 1.20; 95% CI, 1.03-1.40).

The associations were strengthened following further modeling without adjusting for eGFR or UA/Cr: CVD, HR, 1.15; 905% CI, 1.00-1.32; graft failure, HR, 1.83; 95% CI, 1.54-2.18; and mortality, HR, 1.34; 95% CI, 1.15-1.56. When the models were further restricted to participants with eGFR of 15 to 44 mL/min/1.73 m2 (n=1453), findings were comparable: CVD, HR, 1.15; 95% CI, 0.96-1.37; graft failure, HR, 1.65; 95% CI, 1.36-2.01; and mortality, HR, 1.21, 95% CI, 1.00-1.47.

In summary, the researchers said, “Serum phosphorus is marginally associated with CVD, but more strongly associated with graft failure and total mortality in chronic kidney transplant recipients. Adjustment for eGFR and UA/Cr attenuates these associations.”

Source: Merhi B, Shireman T, Carpenter M, et al. Serum phosphorus and risk of cardiovascular disease, graft failure, or all-cause mortality in chronic kidney transplant recipients. Abstract of a poster presented at the National Kidney Foundation 2017 Spring Clinical Meetings, June 21, 2017, Orlando, Florida.