Patients with normal weight (BMI 18.5-25) – unbiased CrCl can be calculated using ideal body weight. and Winter et al., the following adjustments can be made:įor underweight patients (BMI <18.5), actual body weight should be used in the calculations. However, according to the studies of Brown et al. The Cockcroft-Gault body weight controversy still remains unresolved. To account for this problem, clinicians have been discussing different methods of controlling for obesity. Serum creatinine production is associated with lean body mass, not fat, as the muscle tissue is responsible for creatinine production. Abnormal body weight, especially obesity, is one of the problems in the estimation of renal function. However, using this formula is associated with some inaccuracies. Frequently Asked Questions About GFR Estimates.The Cockcroft-Gault equation is the most widely used method of quantifying renal function for drug dosing. Estimating GFR using the CKD Epidemiology Collaboration (CKD-EPI) creatinine equation: more accurate GFR estimates, lower CKD prevalence estimates, and better risk predictions. Comparison of drug dosing recommendations based on measured GFR and kidney function estimating equations. Stevens LA, Nolin TD, Richardson MM, et al.Kidney function estimating equations: where do we stand? Curr Opin Nephrol Hypertens. Prediction of creatinine clearance from serum creatinine. With permission from The National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892-2560. However, for drugs with a narrow therapeutic index, the Cockcroft-Gault equation was less reliable in assessing the risk of kidney damage. The results suggested that, for the majority of patients and for most drugs tested that did not have narrow thresholds for toxicity, there was little difference in the drug dose that would be administered using either equation to estimate kidney function. A large simulation study compared eGFR by MDRD Study equation and estimated creatinine clearance (eCrCl) by the Cockcroft-Gault equation calculated from standardized creatinine values to each other and to measured GFR for the purpose of drug dosing.There is no version of the Cockcroft Gault equation for use with standardized creatinine results.Unfortunately, the creatinine method used in the development of the Cockcroft-Gault equation is no longer in use and samples from the study are not available to evaluate how the results might compare to standardized creatinine values. Creatinine measurement has now been standardized.Is there a role for the Cockcroft-Gault equation? Since the Cockcroft-Gault can overestimate kidney function, there is a risk of overdosing drugs with narrow therapeutic index that has occurred with chemotherapeutic agents.įor more information, see.One study of inpatients receiving aminoglycoside or vancomycin compared the area under the curve for actual drug levels to the eGFR and showed greater precision for the MDRD Study equation. In the few studies that compared estimated GFR from the various equations to measured GFR, the studies have shown that the MDRD Study or CKD-EPI equation had greater concordance with measured GFR than the Cockcroft-Gault. Multiple studies have compared the equations for their impact on drug dosages.The assay used to develop the Cockcroft-Gault was likely 10-20% higher than current methods, therefore use of estimated creatinine clearance calculated using the Cockcroft-Gault will lead to higher drug dosing recommendations than was intended in the original pharmacokinetic studies. Both the MDRD Study and CKD-EPI have been expressed for these reference methods, but the Cockcroft-Gault formula has not.
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