The Usefulness of Spot Urine Protein/Creatinine Ratio in Evaluating Proteinuria in Children and the Correlation between 24-hour Urinary Protein Amount and Spot Urine Protein/Creatinine Ratio

Hong, Seon Young; Kim, Ji Young; Chung, Woo Yeong

Abstract

PURPOSE
Recently, different results about factors affecting accurate quantitation of 24-hr urinary protein(24UP) amount using spot urine protein/creatinine ratio(PCR) have been reported. The current study was designed to evaluate correlation between 24UP amounts and PCR in children, and the effect of 24UP amounts, age, sex, and glomerular filtration rate(GFR) on this correlation.
METHODS
Among 94 patients who visited the department of pediatrics in Busan Paik Hospital from March 2002 to August 2002, 68 patients whose urinary creatinine excretion was > or = 15 mg/kg/day were included in this study. All the patients were divided into I, II/A, B group(I : 24UP < 500 mg/day, II : 24UP > or = 500 mg/day, A : < 10 years of age, B : > or = 10 years of age). Pearson correlation analysis was performed between 24UP and PCR to evaluate the relationship. We defined fractional difference between 24UP and PCR, and then performed multiple regression analysis with 24UP amount, age, GFR and fractional difference.
RESULTS
There was a strong positive linear correlation between 24UP and PCR(R=0.936, P < 0.0001) in all patients, and the correlation was also good in each group. Using PCR cutoff values of 0.5, the PCR provided high sensitivity, specificity, positive and negative predictive value in predicting 24UP amount > or = 500 mg. The factors affecting accurate quantitation of proteinuria using spot urine PCR was age, not 24UP amount, GFR or sex.
CONCLUSION
Spot urine PCR is a useful test but has limitations in predicting 24UP amount. Therefore, it should be used only as screening method. Age-adjusted PCR cutoff values may be necessary to predict 24UP amount in children with proteinuria.