Quantification of proteinuria in children using the urinary protein-osmolality ratio

A prospective study was conducted to determine the correlation of early mor ning urinary protein/osmolality ratio (mg/l/mosmol/kg) with 24-h urinary pr otein excretion (mg/m(2)/day). Study patients consisted of 53 children (age d 1 month to 15 years). Early morning urine samples and 24-h urine samples were collected and analyzed. In group 1 (children without proteinuria), ear ly morning urinary protein/creatinine ratio (Uprot/Ucr, mg/mg) was 0.061+/- 0.011 and the protein/osmolality ratio (Uprot/Uosm, mg/l/mosmol/kg) was 0.0 73+/-0.014. Twenty-four hour urinary protein excretion in group I had no si gnificant correlation with Uprot/Ucr or Uprot/Uosm. In group II (children w ith proteinuria), Uprot/Ucr was 5.78+/-1.10 and Uprot/Uosm was 4.42+/-1.34. Twenty-four hour urinary protein excretion in group 2 was 1483.6+/-303.7 m g/m2/day and its correlation with both Uprot/Uosm and Uprot/Ucr was highly significant (II 0.87, P<0.001 and r=0.88, P<0.001, respectively). The accep ted nephrotic level of proteinuria of 40 mg/m(2)/h coincides with a Uprot/U osm ratio of 1.9. In conclusion, early morning urinary Uprot/Uosm is a simp le and potentially useful test for 24-h urinary protein excretion, and poss ibly could be used safely for the assessment of the degree of proteinuria i n children.