title: Protein-osmolality ratio for quantification of proteinuria in children.
abstract: Proteinuria is an important factor for renal injury and prognosis in many diseases. The most valuable method for evaluation of proteinuria is quantitative protein analysis in appropriately 24-h collected urine. But urine collection is difficult and cumbersome especially in children and working adults. The aim of the present study is to define the usefulness of urinary protein/urine osmolality (Uprot/Uosm) ratio in quantification of proteinuria. One hundred and seventy-one patients whose age ranged between 3 and 14 years were included in the study. Uprot/Uosm (r = 0.85, P < 0.001) and urinary protein/creatinine Uprot/Ucrea (r = 0.81 and P < 0.001) ratios were significantly correlated with 24-h protein excretion. Twenty-four-hour protein excretion was correlated with Uprot/Ucrea (r = 0.76, P < 0.001) and Uprot/Uosm (r = 0.79, P < 0.001) ratios in proteinuric group. But, there was no correlation between Uprot/Uosm and Uprot/Ucrea ratios with 24-h protein excretion in non-proteinuric group. The positive and negative predictive value of Uprot/Uosm ratio of 0.28 mg/l/mOsm/kg was 89.9 and 90.8% and Uprot/Ucrea ratio of 0.24 mg/mg was 85.7 and 90% for estimating proteinuria (above 4 mg/m2 h(-1)). The 95th percentile of Uprot/Uosm ratio was 0.25 mg/l/mOsm/kg and Uprot/Ucrea ratio was 0.27 mg/mg in normal group. The best estimate was Uprot/Uosm ratio of 1.42 (sensitivity 100%, specificity 94.9%) and Uprot/Ucrea ratio of 0.75 (sensitivity 100%, specificity 92.9%) for nephrotic proteinuria (40 mg/m2 h(-1)). Uprot/Uosm which is a reliable and simple method can be used for quantification of proteinuria in pediatric patients with normal renal function. Using Uprot/Uosm ratio for quantification of proteinuria can remove the necessity of 24-h urine collection, urine creatinine measurement and spending additional cost and time if the center measures the urine osmolality routinely in urine analysis.
authors.affiliation: Department of Pediatric Nephrology, Dr. Behcet Uz Children Research Hospital, Izmir, Turkey. serdaroglue@ttmail.com.|, 1374 Sokak No: 26 C Blok Daire: 8, 35210, Alsancak, Izmir, Turkey. serdaroglue@ttmail.com.
authors.forename: Erkin
authors.initials: E
authors.lastname: Serdaroglu
authors.affiliation: Department of Pediatric Nephrology, Ege University Medical School, Izmir, Turkey.
authors.forename: Sevgi
authors.initials: S
authors.lastname: Mir
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D002940:Circadian Rhythm / Q000502:physiology*; D003404:Creatinine / Q000652:urine; D006801:Humans; D009994:Osmolar Concentration; D011237:Predictive Value of Tests; D011507:Proteinuria / Q000175:diagnosis* / Q000652:urine*; D012372:ROC Curve; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index
chemical_list: D003404:Creatinine