Cockcroft-Gault Creatinine Clearance

They are not interchangeable. CKD-EPI eGFR reports mL/min/1.73 m², normalised to body surface area, and exists to stage chronic kidney disease. Cockcroft-Gault reports raw mL/min and is what most drug labels specify for renal dose adjustment, because it is what the original dosing studies used. Substituting one for the other shifts doses, and they disagree most at the extremes of body size and in the elderly — the patients whose dosing is most fragile.

Which weight matters.The 1976 paper used actual body weight. In obesity that overestimates clearance, so ideal or adjusted body weight is often substituted — check what the drug's own labelling assumes rather than guessing.

The equation assumes a steady state. In acute kidney injury, where creatinine is still rising or falling, it lags well behind the true clearance and will flatter the kidneys. It is also unreliable where creatinine production is atypical: marked muscle wasting, amputation, malnutrition or advanced liver disease.

The 0.85 female factor was applied by the authors rather than derived — the original cohort was men.

The 90 / 60 / 30 / 15 bands shown here are the usual regulatory dosing groups, not part of the paper. Individual drugs frequently use their own cut-offs; follow the label.