Serum Phosphorus Associated with Graft Failure and Mortality in Transplant Recipients

Orlando—Kidney transplant recipients may experience mild hyperphosphatemia, a risk factor for cardiovascular disease, loss of renal function, and mortality. There are few data available from large, multicenter cohorts of kidney transplant recipients examining the relationship between serum phosphorus and the development of cardiovascular outcomes, graft failure, or all-cause mortality among chronic, stable kidney transplant recipients.

Basma Merhi, MD, and colleagues conducted an analysis of data from the FAVORIT (Folic Acid for Vascular Outcome Reduction in Transplantation) trial to determine the association of serum phosphorus with the development of cardiovascular disease, graft failure, or mortality. The researchers 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.

At randomization, 3181 FAVORIT trial participants had data on serum phosphorus: mean phosphorus was 3.07 mg/dL. During a median follow-up of 4 years, among the 3181 individuals, there were 445 cardiovascular disease outcomes, 351 deaths, and 242 graft failures.

Using proportional hazards modeling, each 1 mg/dL higher of serum phosphorous was not associated with a significant increase in risk of cardiovascular disease (hazard ratio [HR], 1.06; 95% confidence interval [CI], 0.92-1.22), but was associated with increased graft failure (HR, 1.38; 95% CI, 1.16-1.64) and total mortality risk (HR, 1.20; 95% CI, 1.03-1.40). The models were conducted following adjustments for age, baseline cardiovascular disease, diabetes, smoking, race, sex, body mass index, low-density lipoprotein cholesterol, high-density lipoprotein 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.

When not adjusting for eGFR or UA/Cr, the associations were strengthened: cardiovascular, HR 1.15; 95% 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. Findings were comparable when models were restricted to individuals with eGFR of 15 to 44 mL/min/1.73 m2 (n=1453): cardiovascular, HR 1.15; 95% CI, 0.96-1.37; graft failure, HR 1.65; 95% CI, 1.36-2.10; and mortality, HR 1.21; 95% CI, 1.0-1.47.

In conclusion, the researchers said, “Serum phosphorus is marginally associated with cardiovascular disease, but more strongly associated with graft failure and total mortality in chronic kidney transplant recipients. Adjustments 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, April 19-22, 2017, Orlando, Florida.