[Validity of routinely used methods of testing glomerular filtration in pediatric practice]

The authors compare different methods used commonly in paediatric practice to assess glomerular filtration (GFR)--creatinine clearance and assessment of GFR by means of Schwartz formula with plasma clearance of polyfructosan S (corresponds to inulin plasma clearance). A group of 108 children aged 4-16 years (x = 10.95) was examined. The patients were divided into three groups by the magnitude of polyfructosan S clearance: greater than 100 ml/min/1.73 m2; 50-100 ml/min/1.73 m2 and less than 50 ml/min/1.73 m2. The authors correlated the clearance of polyfructosan S with creatinine clearance and assessment of GFR according to Schwartz. The method which proved to be most sensitive for detection of reduced GFR in the area of 50-100 ml/min/1.73 m2 was creatinine clearance with urine collection one hour after a previous water load (r = 0.748). In the stage of chronic renal failure with GFR less than 50 ml/min/1.73 m2 the correlation was close with the three-hour creatinine clearance (r = 0.957) and equally close was the correlation with GFR according to Schwartz (r = 0.885). The authors discuss the probability of detection of impaired GFR by commonly used methods and draw attention to the advantages of examination of plasma clearance by polyfructosan S.