Validation of plasma clearance of ⁵¹Cr-EDTA in adult renal transplant recipients: comparison with inulin renal clearance

Plasma clearance of ⁵¹Cr-EDTA (⁵¹Cr-EDTA-Cl) is an alternative method to evaluate glomerular filtration rate (GFR). This study aimed to investigate the concordance between ⁵¹Cr-EDTA-Cl and renal inulin clearance (In-Cl) in renal transplant recipients as well to determine the repeatability of ⁵¹Cr-EDTA-Cl in kidney donors. Forty four kidney recipients and 22 kidney donors were enrolled. Simultaneous measurements of ⁵¹Cr-EDTA-Cl and In-Cl were performed. A single dose of 3.7MBq of ⁵¹Cr-EDTA was injected and the plasma disappearance curve was created by taking blood samples at 2, 4, 6 and 8 h after injection. Bland and Altman statistical approach was used to quantify the agreement between In-Cl and ⁵¹Cr-EDTA-Cl and to determine the better concordance between all possibilities of measure for the ⁵¹Cr-EDTA-Cl. The mean of In-Cl was 44.5 ± 17.9 ml/min/1.73 m². There was a positive correlation between In-Cl and all possible measurements of ⁵¹Cr-EDTA-Cl. ⁵¹Cr-EDTA-Cl with two samples taken at 4 and 8 h or at 4 and 6 h presenting the narrow limits of agreement and a difference (bias) of 2.8 and 2.7 ml/min, respectively. Two plasma sampling for ⁵¹Cr-EDTA-Cl was a reliable method to measure GFR compared with In-Cl and comprises a suitable method to be used in kidney transplanted patients.