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Kidney Week

Abstract: TH-PO994

Development of a New Equation for Estimated 24-Hour Proteinuria: Modified Urine Protein-Creatinine Ratio Adjusted by Urinary Creatinine Excretion

Session Information

Category: CKD (Non-Dialysis)

  • 2301 CKD (Non-Dialysis): Epidemiology, Risk Factors, and Prevention

Authors

  • Eriguchi, Masahiro, Nara Medical University, Kashihara, Nara, Japan
  • Furuyama, Riri, Nara Medical University, Kashihara, Nara, Japan
  • Kosugi, Takaaki, Nara Medical University, Kashihara, Nara, Japan
  • Uemura, Takayuki, Nara Medical University, Kashihara, Nara, Japan
  • Tamaki, Hiroyuki, Nara Medical University, Kashihara, Nara, Japan
  • Tasaki, Hikari, Nara Medical University, Kashihara, Nara, Japan
  • Nishimoto, Masatoshi, Nara Medical University, Kashihara, Nara, Japan
  • Tsushima, Hideo, Nara Medical University, Kashihara, Nara, Japan
  • Tanabe, Kaori, Nara Medical University, Kashihara, Nara, Japan
  • Okamoto, Keisuke, Nara Medical University, Kashihara, Nara, Japan
  • Samejima, Ken-ichi, Nara Medical University, Kashihara, Nara, Japan
  • Tsuruya, Kazuhiko, Nara Medical University, Kashihara, Nara, Japan
Background

Instead of the 24h proteinuria, the urinary protein-to-creatinine ratio (Up/Ucr) in spot urine, based on the assumption of 24h urinary creatinine excretion (CER) of 1 g/day, is widely used in clinical practice. However, the actual CER is often deviated from 1g/day because it is affected by individual muscle mass and kidney function, and Up/Ucr is often not accurately estimated for 24h proteinuria.

Methods

Data from a prospective observational study in patients with chronic kidney disease or cardiovascular disease in our hospital were used. Patients with both 24h urine collection and spot urine the day after 24h urine collection were included. First, we examined the relationship between Up/Ucr in 24-hour urine collection and UP/Ucr in spot urine, and then created estimated CER using age, sex, and serum creatinine. Finally, a modified Up/Ucr equation was developed adjusting for estimated CER and the relationship between Up/Ucr in 24-hour urine and UP/Ucr in spot urine.

Results

Among 1031 patients, 813 patients for whom spot urine and 24h urine data were available were included in the analyses of this study. Up/Ucr in spot urine increased by 7% compared to Up/Ucr in 24h urine, and both were closely associated with each other (R2=0.90), suggesting an increase in proteinuria due to exercise in spot urine at hospital visit as compared with 24h urine. Mean CER for males and females was 1.04 and 0.69 g/day, respectively, meaning 4%-overestimation in males and 31% underestimation in females when using Up/Ucr compared with measured 24h proteinuria. CER was also negatively associated with older age especially >60 years and increased in serum creatinine.
The mean difference from measured 24h proteinuria for Up/Ucr in spot urine was -45.4% and that for modified Up/Ucr was -21.2% (P <0.001). The numbers within 15% and 30% of measured 24h proteinuria was 17% and 34% for Up/Ucr in spot urine, respectively and 24% and 46% for modified Up/Ucr, respectively (P <0.001).

Conclusion

Using spot urine immediately after 24-hour urine collection and estimated CER, a modified Up/Ucr equation was newly developed, which could be more useful in clinical practice than classical Up/Ucr.