Creatinine clearance is used to estimate which parameter of kidney function?

• A. Urine osmolality
• B. Blood glucose
• C. Creatinine clearance
• D. Urine sodium

Answer: (C)

The key idea is that glomerular filtration rate (GFR) is the main measure of how well the kidneys are filtering plasma. Creatinine clearance is used in practice to estimate GFR because creatinine is produced at a relatively steady rate and is filtered by the glomeruli with little reabsorption; a small amount is secreted, so the clearance slightly overestimates true GFR, especially as kidney function declines.

In formula terms, creatinine clearance is calculated from urine creatinine concentration, urine flow, and plasma creatinine, and it serves as an accessible proxy for GFR. The other options point to different aspects of kidney function: urine osmolality reflects the kidney’s ability to concentrate or dilute urine, urine sodium reflects tubular handling of sodium, and blood glucose is a metabolic measurement, not a direct measure of filtration.

So, the parameter being estimated is GFR, with creatinine clearance providing a practical estimate of it.