Compar ing Estimated Pr otein Excr etion Rate (ePER) and Spot Ur inar y Pr otein-Cr eatinine Ratio (uPCR) in Assessing Ur inar y Pr otein Excr etion in Patients with Kidney Disease in China: a single center study

Yu Jia ¹ Lingling Zhao ² Fang Wang ³ Jin Shang ^4* Zhanzheng Zhao ^4*

• ¹ First Affiliated Hospital of Zhengzhou University, Clinical Laboratory of Nephrology, Zhengzhou, China
• ² Shanghai lnstitute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, Beijing, China
• ³ First Affiliated Hospital of Zhengzhou University, Department of Hematology, Zhengzhou, China
• ⁴ Department of Nephrology, First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan Province, China

Objectives: This study aimed to analyze the potential of the estimated protein excretion rate (ePER) as a substitute for the spot urinary protein-creatinine ratio (uPCR) in clinical reports for accurately assessing urinary protein excretion in China. Methods: We included 1721 patients in the study and compared the differences in levels, correlation, bias, methodological evaluation between uPCR, ePER, and 24-hour urinary protein.Results: Significant differences(Z = -17.568, p < 0.001) were found between uPCR and 24-hour urine protein levels in all cases. However, no statistically significant difference(Z = -0.652, p = 0.514) was found between ePER and 24-hour urine protein. The bias analysis revealed that the negative bias rate between ePER and 24-hour urine protein was -4.33%, significantly lower compared to uPCR (-30.88%). Incorporating ePER significantly boosted its sensitivity to 91.3% in this cohort. Furthermore, ePER demonstrated a higher correlation(r = 0.74, p < 0.001) and kappa consistency(κ = 0.802, p = 0.015) with 24-hour urinary protein compared to uPCR(r = 0.71, p < 0.001; κ = 0.737, p = 0.016). However, in the > 65 age group, those with estimated glomerular filtration rate (eGFR) < 30 mL/min/1.73m² group and spot urinary creatinine < 500 mg/L exhibited a higher ePER bias compared to uPCR.Conclusions: These findings highlight the potential of ePER as a valuable tool for accurately assessing urinary protein excretion. Nonetheless, its limitations should be considered, especially in specific patient populations.