Key result
Selective use of total, adjusted, and lean body weight by BMI strata in the Cockcroft-Gault equation improved accuracy (≥60.7%) and reduced overestimation bias compared with measured CrCl.
Why the study?
Which body size descriptors provide the most accurate estimation of kidney function across different BMI strata compared to measured creatinine clearance?
Observational (n=590)
Which body size descriptors provide the most accurate estimation of kidney function across different BMI strata compared to measured creatinine clearance?
The accuracy of the Cockcroft-Gault equation in obese patients is significantly improved by using lean body weight for those with BMI ≥40 kg/m2 and total or adjusted body weight for those with BMI <40 kg/m2.
May improve Cockcroft-Gault dosing accuracy in obesity with adjusted weights; hypothesis-generating and should not yet change practice.
BACKGROUND: Dosing adjustments for patients with impaired kidney function are often based on estimated creatinine clearance (eCrCl) because measuring kidney function is not always possible for dose adjustment. However, there is no consensus on the body size descriptor that should be used in the estimation equations. OBJECTIVE: To compare the use of alternative body size descriptors (ABSDs) on the performance of kidney function estimation equations compared with measured CrCl (mCrCl). METHODS: We combined 2 DATA SOURCES: a Food and Drug Administration clinical trial database that includes subjects with body mass index (BMI) less than 40 kg/m(2) and published data from those 40 kg/m(2) or more. The 3 parent equations (Cockcroft-Gault [CG], Modification of Diet in Renal Disease [MDRD], Chronic Kidney Disease-Epidemiology Collaboration [CKDEPI]), and 14 ABSD-modified equations were compared with mCrCl for accuracy, bias, agreement, goodness of fit (R(2)), and prediction error. These equations were also compared across mCrCl and BMI strata. RESULTS: Subjects (n = 590) were aged 19-80 years; 33.9% were female and BMI ranged from 17.2 to 95.6 kg/m(2). Compared with mCrCl, the use of total weight in the CG equation yielded low accuracy (12.5%) and significant bias (-107 mL/min) in the morbidly obese group. In contrast, the use of lean body weights (BMI ≥40 kg/m(2)) and total ± adjusted weights (BMI <40 kg/m(2)) with the CG equation yielded higher accuracy, greater than or equal to 60.7% across all BMI strata, and was unbiased. Transforming the MDRD or CKDEPI equations with body surface area improved accuracy only at mCrCl of 30-80 mL/min and increased the overall prediction error. CONCLUSIONS: No kidney function equation was consistently accurate and unbiased across weight, mCrCl, and estimate ranges. The accuracy and overestimation bias of the CG equation in obese subjects was improved through the selective use of total, adjusted, and lean body weight by BMI strata.
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Park et al. (2012) conducted an observational in Kidney function estimation across BMI strata (n=590). Alternative body size descriptors in kidney function estimation equations vs. Measured creatinine clearance (mCrCl) was evaluated on Accuracy, bias, agreement, goodness of fit, and prediction error compared with measured CrCl. Selective use of total, adjusted, and lean body weight by BMI strata in the Cockcroft-Gault equation improved accuracy (≥60.7%) and reduced overestimation bias compared with measured CrCl.
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