Creatinine excretion rates for renal clearance studies

Area of Science:

• Pediatric Nephrology
• Clinical Chemistry

Background:

• Accurate creatinine excretion rates are crucial for pediatric renal clearance studies.
• Establishing normative data is essential for interpreting these measurements in children.

Purpose of the Study:

• To define the expected range of creatinine excretion rates in children for use in renal clearance studies.
• To evaluate the impact of cimetidine pretreatment on creatinine excretion.
• To compare creatinine excretion between supervised and at-home urine collections.

Main Methods:

• Analysis of 637 timed-urine collections from 295 children aged 2.8–21.7 years over 14 years.
• Comparison of creatinine excretion rates between children pretreated with cimetidine and those not pretreated.
• Statistical comparison of creatinine excretion rates from supervised 2-hour collections versus at-home (approx. 24-hour) collections.

Main Results:

• Cimetidine pretreatment did not significantly alter creatinine excretion rates (P=0.080).
• Supervised urine collections showed significantly higher creatinine excretion rates (1.38 mg/kg/24 h greater, P=0.001) compared to home collections.
• Regression equations were developed to establish age-specific expected creatinine excretion rates.

Conclusions:

• Cimetidine does not affect creatinine excretion rates relevant to clearance studies.
• Supervised urine collections provide more accurate creatinine excretion data than at-home collections in children.
• Prepared tables provide age-based expected creatinine excretion rates for pediatric renal clearance studies.