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

The precision of two different clearance methods as used for 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 injection 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 greater than or equal to 80 ml/min/1.73 m2 was 5.5% for E and 13.8% for C. The corresponding figures for E less than 80 ml/min/1.73 m2 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.