Comparison of 24-hour urinary protein and protein-to-creatinine ratio in the assessment of proteinuria.
To determine the correlation between protein-to-creatinine ratio (PCR) and 24-hour urinary protein (UP), we measured proteinuria in 68 patients attending the nephrology clinic at Jordan University Hospital by 24-hour urine protein excretion and protein-to-creatinine ratio. The cutoff values for spot urine protein-to-creatinine ratio in predicting 24-hour protein "threshold" excretion of 0.5, 1.0 and 3.5 g/day were determined using receiver operating characteristic curves. A very good correlation (r= 0.832, P< 0.0001) was found between spot urine protein-to-creatinine ratio and 24-hour urine protein excretion. Bland-Altman plot showed the two tests had reasonable limits of agreement at low level of protein excretion but the limits became wider as the protein excretion increased. For protein excretion < 2.0 g/day, the limits of agreement of spot urine (PCR) and (UP) were +1.48 and -1.2 g/day. The spot urine protein-to-creatinine ratios of 0.72 (sensitivity 0.97; specificity 1.0), 1.2 (0.97; 0.89) and 3.23 (1.0; 0.86) mg/mg reliably predicted 24-hour urine total protein equivalent "thresholds" of 0.5, 1.0 and 3.5 g/day, respectively. We conclude that the protein-to-creatinine ratio in spot urine specimens is an accurate, convenient, and reliable method to estimate the protein excretion in urine. However, the protein-to-creatinine ratio will likely be within clinically acceptable limits only when proteinuria is at reasonably low levels.
Wahbeh
Ayman M
AM
Department of Internal Medicine, University of Jordan, Amman, Jordan. aymiw@yahoo.com
Ewais
Mohammad H
MH
Elsharif
Mahamed E
ME
D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000652:urine; D003404:Creatinine / Q000652:urine*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011507:Proteinuria / Q000175:diagnosis* / Q000652:urine; D012372:ROC Curve; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013997:Time Factors; D014563:Urodynamics
D015415:Biomarkers; D003404:Creatinine