Comparison of three different methods of estimating the glomerular filtration rate in children after renal transplantation.

In 48 children (aged 3-19 years; 33 males and 15 females), who underwent renal transplantation, the glomerular filtration rates (GFR) estimated from creatinine clearance involving urine collection over 4 h in the hospital under direct supervision and creatinine clearance predicted from plasma creatinine concentrations and height (formula) were compared with the GFR estimated by 99mTc-diethylenediamine penta-acetate (99mTc-DTPA) clearance. There was a good correlation between the three methods (r = 0.8). Measured and formula creatinine clearances overestimated the GFR as determined by 99mTc-DTPA by an average of 19.7 +/- (SD) 21.2 and 21.9 +/- 22.9 ml/min/1.73 m2, respectively. So they should be used with caution to estimate the true GFR. In trying to assess the influence of ciclosporin on creatinine secretion by renal tubules, we compared creatinine clearance in two groups of patients with similar GFR as measured by 99mTc-DTPA, and there was no significant difference in the mean values (p < 0.54) among patients on ciclosporin and azathioprine and on azathioprine alone. It seems, therefore, that ciclosporin did not cause an increased tubular secretion of creatinine leading to an overestimation of the GFR.