Use of the Modification of Diet in Renal Disease (MDRD) study formula may overestimate the number patients with renal dysfunction, according to researchers at the Roswell Park Cancer Institute in Buffalo.

Consequently, patients may be wrongly identified as having renal impairment and be subjected to unnecessary monitoring of renal function, dietary interventions, and medication dose adjustment, said investigator Ali H. Houjaij, MD, a fellow in urologic oncology.

Dr. Houjaij presented findings of a study comparing the accuracy of MDRD study formula with that of the Cockroft-Gault (CG) formula for estimating creatinine clearance in 389 patients undergoing nephrectomies (263 radical and 126 partial nephrectomies) for renal tumors. The study, led by Hung L. Kim, MD, associate professor of oncology at Roswell, compared these estimates with creatinine clearance measurements obtained using 24-hour urine collections.

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Based on CG estimates, renal dysfunction developed in 23% of patients following radical nephrectomy and 11% of patients following partial nephrectomy. In contrast, using MDRD, renal dysfunction developed in 61% following radical nephrectomy and 22% of patients following partial nephrectomy.

Dr. Houjaij noted that the study was conducted because investigators have started using the MDRD equation without validating its accuracy in the populations of patients being surgically managed for renal tumors. As a result of study findings, clinicians at his institution now prefer to use the CG instead of the MDRD formula, he said.