Summary
Usage Cockcroft-Gault (CG) equation was the the first (1976) equation to estimate kidney function using non-standardized creatinine measurements for determining creatinine clearance, which estimates glomerular filtration rate (GFR). Primary uses include chronic kidney disease staging, and discontinuing or adjusting medication dosage. While creatinine clearance may over-estimate GFR by 10-20%, creatinine clearance is the standard for drug dosing adjustments. The CG equation has fallen out of favor with the advent of newer creatinine assays using internationally standardized creatinine measurements which has a tendency to bias the CG equation toward overestimation of GFR (10-40%). Additionally, variations in body composition among patients can also contribute to inaccuracies at weight extremes (Brown, 2013 & Winter, 2012). Based on expert opinion, additional adjustments to the CG equation are included based on body weight and BMI. Despite these limitations, the CG equation remains relevant as may drug dosing recommendation for patients with decreased kidney function were based on creatinine clearance calculations from the CG equation. Note: The estimated GFR measured in the MDRD and the CKD-EPI equations demonstrate better concordance with measured GFR that does the CG equation. These equations are also appropriate for determining drug dosing.. Summary The Cockcroft-Gault (CG) Equation is one of many methods employed to estimate creatinine clearance. To improve accuracy researchers have recommended additional adjustments to the CG equation to address inaccuracies at weight extremes (Brown, 2013 & Winter, 2012). Additional weight adjustments are made based on Body Mass Index (BMI), to include ideal body weight (IBW) and adjusted body weight (ABW). The weight adjustments are not included in this tool. Refer to the Creatinine Clearance with adjustment options located on the Explore page. RulesCreatinine Clearance (CrCl), mL/min: Cockcroft-Gault Equation=(140 - age) x (weight, kg) x (0.85 if female) / (72 x Creatinine, mg/dL)