Cockcroft-Gault Formula

The Cockcroft and Gault formula (CG) was developed in 1973 using data from 249 men with creatinine clearance (CCr) from approximately 30 to 130 mL/m2. It is not adjusted for body surface area. CG is no longer recommended for use because it has not been expressed using standardized creatinine values.

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The Cockcroft and Gault formula (1973)

C_Cr={((140–age) x weight)/(72xS_Cr)}x 0.85 (if female)

Abbreviations/ Units

C_Cr (creatinine clearance) = mL/minute

Age = years

Weight = kg

SCr (serum creatinine) = mg/dL

Why is the Cockcroft-Gault formula provided on this website?

• The Cockcroft-Gault (CG) formula is provided on this website for research purposes only. It should not be used for drug dosing or to estimate GFR.
• The best way to determine drug dosing is with the CKD-EPI Creatinine Equation (2009) or the MDRD Study. Both have been shown to be more accurate than the CG formula.

Why isn’t the Cockcroft-Gault formula recommended for clinical use?

• The Cockcroft-Gault (CG) formula has not been expressed using standardized creatinine values. This means it will give inaccurate results. It is not recommended for clinical use.
• Creatinine assays are standardized to reference methods. Both the MDRD Study and CKD-EPI have been expressed for these reference methods, but the Cockcroft-Gault formula has not. 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.
• Multiple studies have compared the equations for their impact on drug dosages. 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. 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.
• 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.

For more information, see http://ckdepi.org/equations/drug-dosing/.

Is there a role for the Cockcroft-Gault equation?

• Creatinine measurement has now been standardized. 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.
• There is no version of the Cockcroft Gault equation for use with standardized creatinine results.
• 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. 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. However, for drugs with a narrow therapeutic index, the Cockcroft-Gault equation was less reliable in assessing the risk of kidney damage.

With permission from The National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892-2560.

References

1. Cockcroft, D.W. and M.H. Gault. Prediction of creatinine clearance from serum creatinine. Nephron. 1976. 16(1):31-41.
2. Coresh, J. and L.A. Stevens. Kidney function estimating equations: where do we stand? Curr Opin Nephrol Hypertens. May 2006;15(3): 276-84.
3. Stevens LA, Nolin TD, Richardson MM, et al. Comparison of drug dosing recommendations based on measured GFR and kidney function estimating equations. Am J Kidney Dis. 2010;55(4):660-670.
4. Levey AS, Stevens LA. Estimating GFR using the CKD Epidemiology Collaboration (CKD-EPI) creatinine equation: more accurate GFR estimates, lower CKD prevalence estimates, and better risk predictions. Am J Kidney Dis. Apr 2010;55(4):622-627.
5. Inker, AS. Frequently Asked Questions About GFR Estimates. New York: The National Kidney Foundation; 2011