Using Kinetic eGFR for drug dosing in AKI:concordance between Kinetic eGFR and Cockroft Gault eCrCl for drug dosing categories in a pilot study cohort

Introduction

Drug dosing in AKI is based on the Cockroft Gault equation derived eCrCl(CGeCrCl) for historical reasons due to the lack of a validated method for estimating GFR when the creatinine(Cr) is rapidly changing. The kinetic equation by Chen (KeGFR) estimates GFR for the non-steady state Cr level and is being validated in patient cohorts. In our pilot study¹ we applied the KeGFR equation to detect AKI. KeGFR could potentially be used for drug dosing in patients with AKI. We examined the concordance of KeGFR with CGeCrCl and MDRDeGFR based drug dosing categories in our study cohort.

Methods

Eighty patients with a significant change in Cr level after admission to the acute medical ward were classified as per AKIN and RIFLE criteria and compared to a KeGFR based criterion in the pilot study. We applied the CG equation and the MDRD equation to the same cohort of patients and studied the concordance between the eGFR values by the 3 methods.We used 3 eGFR categories (<30, 30-49 and >50 ml/min) reflecting the renal drug dosing thresholds for commonly used drugs in patients with AKI.Pearsons coefficent and  Cohen's Kappa were used as appropriate.

Results

Though the Pearson’s coefficient indicated a high correlation (0.85) between the values for KeGFR and CGeCrCl, the agreement between the methods for drug dosing categories was poor (Kappa 0.40) and the concordance was also poor (62%) with 27(90%) of the 30 discordant subjects falling into a higher eGFR category when KeGFR was used. There was better concordance (75%) and agreement (Kappa 0.76) between MDRDeGFR and KeGFR for the drug dosing categories.

Conclusions