Background Urine protein/creatinine ratio (uPCR) offers practical advantages over 24-hour urine protein (24hUP) for quantifying proteinuria in kidney diseases, but its correlation and agreement with 24hUP (the diagnostic gold standard) remain unvalidated in ANCA-associated glomerulonephritis (AAGN). Methods This retrospective study analyzed 164 paired uPCR and 24hUP measurements obtained on the same or following day from 87 AAGN patients. Paired uPCR and 24hUP data were grouped by 24hUP levels: < 500, 500–3500, > 3500 mg/day. Correlation was assessed using Spearman’s correlation coefficient (ρ); agreement was evaluated via Intraclass correlation coefficient (ICC) and Concordance correlation coefficient (CCC). Sensitivity and specificity of uPCR percentage changes for predicting 24hUP percentage changes were calculated in 56 patients undergoing inpatient therapy. Results The uPCR strongly correlated with 24hUP across all groups: ρ = 0.616 (< 500 mg/day), 0.794 (500–3500 mg/day), and 0.758 (> 3500 mg/day) (all p < 0.05). However, agreement was suboptimal (ICCs: 0.373, 0.633, 0.458; CCCs: 0.369, 0.635, 0.432.). Percentage changes in uPCR during treatment highly correlated with 24hUP percentage changes (r = 0.886, p < 0.001). A 20% uPCR decrease predicted 20% 24hUP reduction with 97% sensitivity/90% specificity; thresholds of 40% and 60% maintained high accuracy (sensitivity 90, 96%, specificity 93, 95%). Conclusion While uPCR correlated strongly with 24hUP in AAGN (especially at 500–3500 mg/day), poor agreement supported retaining 24hUP for initial diagnosis. The uPCR percentage changes reliably reflected therapeutic response with a median interval of 14 days (IQR 8–25), offering a practical alternative for monitoring hospitalized patients. <Table Float="No" ID="Taba"> <tgroup cols="2"> <colspec align="left" colname="c1" colnum="1" /> <colspec align="left" colname="c2" colnum="2" /> <tbody> <row> <entry align="left" nameend="c2" namest="c1"> Key Points • The correlation between uPCR and 24hUP in AAGN was strong (particularly at 24hUP levels of 500–3500 mg/day), but the agreement between them was poor. • It was still recommended to retain 24hUP for initial proteinuria quantification in AAGN. • Monitoring of uPCR percentage changes may substitute for 24hUP measurements in assessing renal therapeutic response in AAGN. </entry> </row> </tbody> </tgroup> </Table>

Comparison of urine protein/creatinine ratio with 24-hour urine protein in ANCA-associated glomerulonephritis

期刊论文
发表日期：

2025年12月18日

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Shijian Fan,
Jiaqing Liu,
Bing Chen,
Jie Yao,
Qiang Zhou

摘要

Background

Urine protein/creatinine ratio (uPCR) offers practical advantages over 24-hour urine protein (24hUP) for quantifying proteinuria in kidney diseases, but its correlation and agreement with 24hUP (the diagnostic gold standard) remain unvalidated in ANCA-associated glomerulonephritis (AAGN).

Methods

This retrospective study analyzed 164 paired uPCR and 24hUP measurements obtained on the same or following day from 87 AAGN patients. Paired uPCR and 24hUP data were grouped by 24hUP levels: < 500, 500–3500, > 3500 mg/day. Correlation was assessed using Spearman’s correlation coefficient (ρ); agreement was evaluated via Intraclass correlation coefficient (ICC) and Concordance correlation coefficient (CCC). Sensitivity and specificity of uPCR percentage changes for predicting 24hUP percentage changes were calculated in 56 patients undergoing inpatient therapy.

Results

The uPCR strongly correlated with 24hUP across all groups: ρ = 0.616 (< 500 mg/day), 0.794 (500–3500 mg/day), and 0.758 (> 3500 mg/day) (all p < 0.05). However, agreement was suboptimal (ICCs: 0.373, 0.633, 0.458; CCCs: 0.369, 0.635, 0.432.). Percentage changes in uPCR during treatment highly correlated with 24hUP percentage changes (r = 0.886, p < 0.001). A 20% uPCR decrease predicted 20% 24hUP reduction with 97% sensitivity/90% specificity; thresholds of 40% and 60% maintained high accuracy (sensitivity 90, 96%, specificity 93, 95%).

Conclusion

While uPCR correlated strongly with 24hUP in AAGN (especially at 500–3500 mg/day), poor agreement supported retaining 24hUP for initial diagnosis. The uPCR percentage changes reliably reflected therapeutic response with a median interval of 14 days (IQR 8–25), offering a practical alternative for monitoring hospitalized patients.

Key Points

• The correlation between uPCR and 24hUP in AAGN was strong (particularly at 24hUP levels of 500–3500 mg/day), but the agreement between them was poor.

• It was still recommended to retain 24hUP for initial proteinuria quantification in AAGN.

• Monitoring of uPCR percentage changes may substitute for 24hUP measurements in assessing renal therapeutic response in AAGN.