Different equations used to qualify patients for the kidney transplant waitlist may yield different results and lead to inequities, according to a study presented at ASN Kidney Week 2015. On average, one of the kidney function equations used when placing patients on the waiting list delayed the order for kidney transplant by one or two years, compared to the other two equations studied.

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Benjamin J. Lee, MD, from the University of California, San Francisco, and his colleagues assessed the relative performance of three commonly used kidney function equations used when placing patients on the waiting list, termed Cockroft-Gault, MDRD, and CKD-EPI. Approximately 4% to 6% of patients on the kidney transplant waitlist die each year, and patients may benefit from being placed on the list sooner, the study authors said.

The team found that choice of equation led to significant and consistent differences in qualification time when applied to three different patient cohorts: a group of waitlisted patients at one major U.S. academic center and two national, multicenter study groups of CKD patients, one with only African Americans and the other with predominantly Caucasians. The Cockroft-Gault equation most often disadvantaged patients as compared with the MDRD and CKD-EPI equations.

On average, time to waitlist qualification would be delayed on the order of one to two years by using the Cockroft-Gault equation, as compared with the MDRD equation or CKD-EPI equation.

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“Given the high observed mortality rates for patients on the waitlist and median wait times of 1.4 to 3.3 years, depending on geographic location, for deceased donor transplants in the United States, the magnitude of these differences is concerning,” said Lee. “The Organ Procurement and Transplantation Network may need to revise the language in kidney transplantation policies so that consistent methods to assess kidney function are adopted and patients are not inadvertently disadvantaged.”