What is the test that measures the rate at which creatinine is cleared from the blood by the kidneys?

• A. Glomerular Filtration Rate
• B. Serum Creatinine
• C. Blood Urea Nitrogen Test
• D. Creatinine Clearance Test

Answer: (D)

Creatinine clearance directly measures how quickly creatinine is removed from the blood by the kidneys, giving a clearance rate that reflects renal filtering. It’s calculated from the amount of creatinine in urine and the urine volume over a collection period, divided by the plasma creatinine concentration, and the result is expressed as mL per minute. Because creatinine is produced at a relatively steady rate and is freely filtered at the glomerulus with only a small amount secreted, this clearance value mirrors the kidneys’ filtration capacity. Serum creatinine, by contrast, is just a blood concentration marker and doesn’t describe how fast creatinine is cleared. Glomerular filtration rate describes the overall rate at which the kidneys form filtrate, not specifically the clearance of creatinine. The blood urea nitrogen test measures another waste product and doesn’t assess creatinine clearance. So the test that measures the rate at which creatinine is cleared from the blood by the kidneys is the creatinine clearance test.