A comparison of single plasma sample methods to estimate renal clearance using 99mTc‐ethylenedicysteine and 99mTc‐mercaptoacetyltriglycine

Several single sample methods for determination of ^99mTc‐mercaptoacetyltriglycine (MAG3) clearance are being used clinically. Kabasakal et al. proposed a similar formula for ^99mTc‐ethylenedicysteine (EC). This study was performed to compare his method with Bubeck et al. formula for ^99mTc‐MAG3 already in use. Twenty‐eight subjects divided in two groups were registered which included 22 patients with various renal diseases (group‐I) and six normal volunteers (group II). All subjects were studied twice using both the radiopharmaceuticals. The images and renogram parameters, that is T_MAX and T_1/2 of both the agents, were similar in all the subjects. The clearance of the ^99mTc‐EC was however considerably higher than ^99mTc‐MAG3 in both the groups (mean ± SEM =279 ± 14 ml min^?1/1·73 m² versus 177 ± 15 ml min^?1/1·73 m² in group‐I and 377 ± 11·90 ml min^?1/1·73 m² versus 238 ± 8·23 ml min^?1/1·73 m² in group II). This difference was more pronounced in cases with reduced renal functions. Among the Effective Renal Plasma Flow (ERPF) values determined from EC and MAG3 clearances in six normal volunteers, four cases only in MAG3 had ERPF below the lower limit. This study has demonstrated superiority of single sample method for ^99 mTc‐EC clearance over its analogous method for ^99mTc‐MAG3.