The role of urinary spot protein/creatinine ratio to estimate the amount of daily proteinuria in patients with glomerulonephritis

Background: Quantifying protein in urine is commonly used in the diagnosis of kidney diseases, measuring the efficiency of the treatment and evaluation of prognosis. We aimed to perform a prospective evaluation of urinary spot Protein/Creatinine ratio accuracy in estimation of proteinuria in patients with various glomerulonephritis.Methods: The correlation between P/C in random urine specimens and urinary protein excretion in 24-h collections in pre- and post-treatment periods were evaluated in 38 adults. Diagnostic accuracy of the P/C ratio was evaluated by receiver-operator curves (ROC) to predict different threshold levels of protein excretion (0.3 and 3 gram/day).Results: A linear relationship exists between spot P/Cr and 24 h protein excretion, with a significant correlation in both pre and post treatment values (p<0.0001). The deviation between the methods increased parallel to the amount of proteinuria. The low creatinine producer patients with high proteinuria had a higher deviation between the methods at high proteinuria levels than high creatinine producers. The areas under curve by ROC curve analysis performed to detect pre and post treatment urine protein excretion of 0.3 and 3 g in 24-h collections were >0.95.Conclusion: The P/C in spot urine samples could be used as an alternative to urine protein excretion in 24-h collections. But it is unreliable in patients with high protein excretion. Accuracy of the method needs to be clarified in patient with low creatinine production.