Precision of single injection 51 Cr EDTA plasma clearance and endogenous creatinine clearance determinations in children

The precision of two different clearance methods as used routine assessment of the glomerular filtration rate (GFR) was investigated in thirty-one children aged 0.6-14 years:total 51Cr EDTA plasma clearance (E) determined by a simplified single method; and 24 h endogenous creatinine clearance (C). Determination of C twice only succeeded in twenty children because of problems in collecting 24 h urine accurately. The precision (determined from the total day-to-day variation) for single determinations in patients with E>=80 ml/min/1.73 m 2 was 5.5% for E and 13.8% for C. The corresponding figures for E<80 ml/min1.73m 2 was 7.8% for E and 20.8% for C. Data in the literature on the inaccuracies of C and E versus GFR suggest that the degree of inaccuracy in predicting GFR from C is much higher than that from E, a feature which together with the present findings on precision indicates that E is much more reliable than C for routine determination of GFR in children. (Auth.)