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J Nephrol. 2004 Sep-Oct;17(5):666-72.

Is morning urinary protein/creatinine ratio a reliable estimator of 24-hour proteinuria in patients with glomerulonephritis and different levels of renal function?

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  • 1Renal Division Hospital de Clinicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.



This cross-sectional study was conducted to determine whether a spot urine protein/creatinine ratio (UPr/UCr) provides accurate quantitation of 24-hr urinary protein excretion (24-hr Prot) in out-patients with primary glomerulonephritis (GN) and different renal function levels.


Patients were classified into three groups according to creatinine (Cr) clearance (ml/min) and into five categories according to morning UPr/UCr. Correlation between 24-hr Prot and UPr/UCr was calculated according to the three renal function levels. The Bland and Altman method was used to assess agreement between 24-hr Prot and UPr/UCr. Agreement limits were obtained calculating the mean difference between 24-hr Prot and morning UPr/UCr +/- 2SD. Sensitivity and specificity were determined for different renal function levels and UPr/UCr cut-off values.


High correlation coefficients (r=0.91, 0.95 and 0.98) were observed in patients with normal, reduced and severely reduced renal function. Differences and variability between 24-hr Prot and UPr/UCr tended to increase with higher proteinuria levels, and this trend was observed for the three renal function levels. The best UPr/UCrcut-off values to detect abnormal or nephrotic proteinuria were, respectively, 0.3 and 2.6.


Correlation and agreement between UPr/UCr and 24-hr Prot was good for all renal function levels, but demonstrated more marked differences as urinary protein excretion increased. Morning UPr/UCr had good sensitivity and specificity for the diagnosis of 24-hr Prot, even in patients with reduced renal function.

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