For a creatinine clearance test, which statement is true?

• A. The test uses only a blood sample.
• B. A 24-hour urine collection is not required.
• C. It requires a 24-hour urine collection and the test should be restarted if any urine is missed.
• D. Only the first urine of the day is needed.

Answer: (C)

Creatinine clearance measures how well the kidneys are filtering by comparing creatinine levels in blood with creatinine cleared into urine over a 24-hour period. To get an accurate result, you need a full 24-hour urine collection and a blood creatinine measurement. Typically, the first morning urine is discarded to start the timing, and all urine produced during the next 24 hours is collected. If any urine is missed, the collection is invalid and must be restarted to avoid underestimating the clearance. So this statement is true because it reflects both the 24-hour collection and the restart rule. The other ideas aren’t accurate because this test requires urine collection over a full day and cannot be done with just a blood sample or with only the first urine.