Predict GFR in a 50-year-old woman who weighs 60 kg using the Cockcroft-Gault equation. Her serum creatinine level is 2.5 mg/dL.

• A. 20 mL/min
• B. 25.5 mL/min
• C. 40 mL/min
• D. 60 mL/min

Answer: (B)

The main idea here is using the Cockcroft-Gault equation to estimate creatinine clearance, a practical stand‑in for GFR in adults. This formula incorporates age, body weight, sex adjustment, and serum creatinine to approximate how well the kidneys are filtering.

For a 50-year-old woman weighing 60 kg with a serum creatinine of 2.5 mg/dL, apply the equation: CrCl = [(140 − age) × weight × 0.85] / (72 × Scr). The 0.85 factor is used for females. Plugging in the numbers: (140 − 50) = 90; 90 × 60 = 5400; 5400 × 0.85 = 4590; denominator is 72 × 2.5 = 180. Then 4590 / 180 = 25.5 mL/min.

So the predicted GFR (as creatinine clearance) is about 25.5 mL/min. This reflects reduced kidney function consistent with an elevated serum creatinine. The other numbers would require different inputs (lower serum creatinine, greater weight, or younger age) to reach those values, but with these inputs the calculation clearly yields around 25.5 mL/min.