Creatinine Clearance (Cockcroft-Gault Equation)
For use in patients with stable renal function to estimate creatinine clearance.
- Can be used to estimate kidney function for CKD staging.
- Can be used to adjust or discontinue medications based on kidney function.
- The original Cockcroft-Gault equation, derived in 1976, relied on non-standardized creatinine measurements. With the use of internationally standardized creatinine measurements, the equation significantly overestimates the GFR (10-40%).
- Because it includes weight in the equation, the output of the CG equation is in ml/min (compare to MDRD or CKD-EPI, with output units of ml/min/1.73m2).
From Dan Brown, PharmD, at Palm Beach Atlantic University, the primary author of the functional range of creatinine clearance paper:
“The Cockcroft-Gault equation remains the gold standard after almost 40 years, despite inaccuracies that arise from variations in body composition among patients. Those who understand potential sources of error can adjust accordingly.”
- While the Cockcroft-Gault equation was the first and is the most well-known estimating equation for kidney function, it has largely fallen out of favor in clinical practice due in large part to its propensity to overestimate GFR using newer creatinine assays, with both the MDRD and CKD-EPI equations performing better across a variety of populations.
- However, many drug dosing recommendations for patients with decreased kidney function were based on creatinine clearance calculations from the CG equation, and it remains one option for determining drug dosage and discontinuation. Evidence suggests that eGFR measured by both MDRD and CKD-EPI show better concordance with measured GFR than does the CG equation, and so the use of these equations is appropriate for determining drug dosing.
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From the Creator
Insights from Dr. Cockcroft:
Calculating creatinine clearance was a "simple" resident research project designed by Dr. Henry Gault, my mentor at the time. We set out to evaluate the accuracy of a creatinine clearance nomogram by Siersbaek-Nielsen (1971). Our data, almost identical to that used to create the nomogram, resulted in our formula.
As an asthma specialist, kidney function is not in my area of expertise. I suspect that some key recommendations may occasionally be overlooked. This includes the requirement for renal function to be in a steady state. It is also likely to be inaccurate in significant obesity and fluid retention when "ideal weight" should probably be used. Also, importantly, the formula presumes normal muscle mass and function and will be inaccurate in cases of significant muscle disease, including muscle wasting.
About the Creator
Donald W. Cockcroft, MD, is a professor of medicine at the University of Saskatchewan. He is co-chair of Airways Research Group and the chair of the Quality Assurance Committee. Dr. Cockcroft specializes in asthma practice and research.
To view Dr. Donald Cockcroft's publications, visit PubMed
About the Creator
Henry Gault, MD, MSc, (d. 2003) was named professor emeritus in 1993 after nearly 20 years as a physician and professor at Memorial University of Newfoundland. He was also director for the Division of Nephrology at the General Hospital and of the Renal Laboratory. Dr. Gault was a pioneer in the field of nephrology and his work on urine enzymology was a major influence on the discovery of the diagnosis of the rejection of kidney transplants.
To view Dr. Henry Gault's publications, visit PubMed