Population-Based Limits of Urine Creatinine Excretion

Area of Science:

• Nephrology
• Clinical Chemistry
• Biostatistics

Background:

• Timed urine collections are crucial for assessing kidney function.
• Current creatinine excretion limits for validating urine collections may be unreliable.
• Accurate validation is essential for dependable clinical and research data.

Purpose of the Study:

• To empirically derive population-based limits for urine creatinine excretion.
• To establish more reliable criteria for evaluating the validity of timed urine collections.
• To improve the accuracy of diagnostic and research data derived from urine samples.

Main Methods:

• Utilized data from 9199 participants across four large cohort studies (CRIC, MDRD, JHS, PREVEND).
• Developed a predictive model for 24-hour urine creatinine excretion using weight, height, age, and sex.
• Assessed model performance using R-squared, bias, precision, and agreement analyses.

Main Results:

• A sex-specific model incorporating weight, height, and age accurately predicted urine creatinine excretion (R-squared = 0.328).
• The model demonstrated good precision and low bias in a validation cohort.
• Serum creatinine marginally improved precision but reduced bias in advanced chronic kidney disease (CKD) patients.

Conclusions:

• The derived population-based limits provide the most valid and representative data for assessing timed urine collection adequacy.
• These new limits enhance the reliability of urine collection validity assessments.
• Improved validation of urine collections supports more accurate clinical and research outcomes.