Higher serum phosphorus levels in kidney transplant recipients (KTR) are associated with increased risks for allograft failure and premature death, according to a new study.

Serum phosphorus levels were measured at baseline in 3138 participants in the FAVORIT (Folic Acid for Vascular Outcome Reduction in Transplantation; NCT00064753) trial. Mean phosphorus levels were 3.07 mg/dL, and ranged from 0.79 to 8.32 mg/dL.

During 4 years of follow-up, 436 cardiovascular disease (CVD) events, 238 transplant failures, and 348 deaths occurred, according to results published in the American Journal of Kidney Diseases (2017;70:377-385). Andrew Bostom, MD, MS, of Rhode Island Hospital in Providence, Rhode Island, and his team reported that each 1-mg/dL rise in serum phosphorus was associated with a significant 36% and 21% greater risk for transplant failure and all-cause mortality, respectively, and a non-significant 6% increase in CVD risk. Patients in the highest decile of serum phosphorus (3.93 mg/dL or higher) had double the risk of transplant failure compared with those in the lowest quintile (2.51 mg/dL or lower), in an adjusted model.

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The investigators adjusted their models for estimated glomerular filtration rate, urinary albumin to creatinine ratio, treatment allocation (vitamin B), CVD risk factors, type of kidney transplant (living or cadaveric), transplant vintage, and use of calcineurin inhibitors, steroids, and lipid-lowering drugs. Information on parathyroid hormone, fibroblast growth factor 23, and vitamin D metabolites was lacking, which was a study limitation.

“Our data suggest that KTRs merit a randomized controlled clinical trial that assesses the potential impact of phosphorus-lowering therapy on hard outcomes in this CKD population, such as CVD, all-cause mortality, and the development of kidney transplant failure—the last outcome, especially,” Dr Bostom and colleagues concluded.

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Merhi B, Shireman T, Carpenter MA, et al. Serum phosphorus and risk of cardiovascular disease, all-cause mortality, or graft failure in kidney transplant recipients: An ancillary study of the FAVORIT trial cohort. Am J Kidney Dis. 2017 Sep;70(3):377-385. doi: 10.1053/j.ajkd.2017.04.014