Urinary Protein Selectivity in Childhood Nephrotic Syndrome

Urinary protein selectivity was determined in 40 pediatric patients with nephrotic syndrome by calculating the relative clearance of IgG and transferrin with the single radial immunodiffusion technique. Among them, 32 cases were classified as idiopathic and 8 as secondary type. The patients in the idiopathic variety were divided into two groups by the selectivity angle 60o. In the group of 20 cases with good selectivity, 16(80%) responded well to corticosteroid therapy, only 3(15%) had hematuria, and none was hypertensive. In the group of 12 cases with poor selectivity, none had a satisfactory response to steroid therapy. Hematuria (9 cases-75%) and hypertension (5 cases-41%) were more frequently encountered in the latter group. Both the difference in the occurrence of hematuria and hypertension, and that in the response to steroid therapy between these two groups were statistically significant. All cases with the secondary type had poor urinary protein selectivity, suggesting severe glomerular injuries due to their underlying diseases. It is concluded that the measurement of urinary protein selectivity is a safe and reliable technique in estimating the functional integrity of the glomerular filter. It can be used to predict the response to steroid therapy in childhood nephrotic syndrome and is also very helpful in differentiating the idiopathic from the secondary type.