Glomerular Filtration Rate Equations Overestimate Creatinine Clearance in Older Individuals Enrolled in the Baltimore Longitudinal Study on Aging: Impact on Renal Drug Dosing

Objectives To evaluate the performance of kidney function estimation equations and to determine the frequency of drug dose discordance in an older population. Design Cross‐sectional analysis of data from community‐dwelling volunteers randomly selected from the Baltimore Longitudinal Study of Aging from January 1, 2005, to December 31, 2010. Subjects A total of 269 men and women with a mean ± SD age of 81 ± 6 years, mean serum creatinine concentration (Scr) of 1.1 ± 0.4 mg/dl, and mean 24‐hour measured creatinine clearance (mClcr) of 53 ± 13 ml/minute. Measurements and Main Results Kidney function was estimated by using the following equations: Cockcroft‐Gault (CG), Modification of Diet in Renal Disease (MDRD), and Chronic Kidney Disease Epidemiology Collaboration (CKD‐EPI). The performance of each equation was assessed by measuring bias and precision relative to mClcr. Dose calculation errors (discordance) were determined for 10 drugs requiring renal dosage adjustments to avoid toxicity when compared with the dosages approved by the Food and Drug Administration. The CG equation was the least biased estimate of mClcr. The MDRD and CKD‐EPI equations were significantly positively biased compared with CG (mean ± SD 34 ± 20% and 22 ± 15%, respectively, p