Creatinine Clearance Calculation — FRCA Primary MCQ

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HardPhysiology - RenalCreatinine Clearance CalculationFRCA Primary

A timed urine sample contains creatinine 8 mmol/L. Plasma creatinine is 80 micromol/L and urine volume is 90 mL collected over 30 minutes. What is the approximate creatinine clearance?

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Correct answer: E — 300 mL/min

The best answer is “300 mL/min”. Convert urine creatinine to 8000 micromol/L and urine flow to 3 mL/min: clearance = 8000 × 3/80 = 300 mL/min. The result is physiologically high and may reflect collection or assay conditions; the calculation itself remains correct. Creatinine clearance can overestimate true GFR because of tubular secretion.

Reference: RCoA, Primary FRCA syllabus: https://www.rcoa.ac.uk/sites/default/files/documents/2026-01/Primary-FRCA-Syllabus.pdf; Measurement of renal function in chronic kidney disease: https://pmc.ncbi.nlm.nih.gov/articles/PMC3791974/