TC-99M L,L-ETHYLENEDICYSTEINE CLEARANCE AND CORRELATION WITH I-125 ORTHOIODOHIPPURATE FOR THE DETERMINATION OF EFFECTIVE RENAL PLASMA-FLOW

Technetium-99m L,L-ethylenedicysteine (Tc-99m-L,L-EC) is a new renal t ubular tracer that allows the determination of the effective renal pla sma flow (ERPF). The aim of this study was to derive simplified method s for the estimation of (TC)-T-99m-L,L-EC Clearance using one or two p lasma samples after bolus injection, Fifty-nine multiple plasma dual-t racer samples (nine samples from 5 to 120 min after injection) were ob tained after injection of kit-formulated Tc-99m-L,L-EC and iodine-125 orthoiodohippurate (OIH). The studies were performed in 25 stable and 24 unstable transplant recipients, in five patients with renal insuffi ciency (four on chronic haemodialysis) and in five normal volunteers. This allowed a wide range of renal function values to be covered, with ERPF (estimated by OIH clearance) ranging from 25.4 to 604.0 ml/min. The reference Tc-99m-L,L-EC clearance, as calculated from the multisam ple model, could be estimated from two samples at 15 and 90 min with a n error of 11.3 ml/min and from one sample at 90 min with an error of 17.8 ml/min. Using appropriate linear regression analysis, ERPF could be estimated by the two- and one-sample Tc-99m-L,L-EC clearance with a n error of 24.2 and 22.8 ml/min, respectively. In conclusion, Tc-99m-L ,L-EC clearance can be accurately estimated by simplified one- or two- sample methods. Moreover, these methods can be used to estimate ERPF w ith an error that remains acceptable for clinical purposes.