Jødal Lars, Brøchner-Mortensen Jens
Department of Nuclear Medicine and Center for Cardiovascular Research, Aalborg Hospital, Aarhus University Hospital, Aalborg, Denmark.
Scand J Clin Lab Invest. 2009;69(3):305-13. doi: 10.1080/00365510802566882.
Total plasma clearance of (51)Cr-EDTA, Cl, is widely used as a measure of GFR. Commonly, only the final part of the plasma concentration curve is measured, and a one-pool clearance (slope-intercept clearance), Cl(1), is computed. Empirically determined second-order polynomials of the general form Cl = b x Cl(1) + c x Cl(1)(2) are usually used to estimate Cl from a measured Cl(1). However, theoretical considerations indicate that such corrections underestimate Cl at high values.
To derive an analytically correct relationship between Cl and Cl(1) and determine the parameters involved for children and adults.
Cl was determined in 149 subjects (M/F/children: 71/46/32) from a complete plasma concentration curve followed for 4-5 h after injection of (51)Cr-EDTA (range of clearance: 8-183 mL/min/1.73 m(2)). Plasma volume, PV and the "missing" area under the plasma fraction curve, a (minutes), not used for determination of Cl(1), were measured.
The true relationship between Cl and Cl(1) is given by Cl = Cl(1)/(1 + f x Cl(1)), where f = a/PV. For men, women and children alike, the equation f = 0.0032 x BSA(-1.3) was applicable (BSA = body surface area in m(2)). Estimation errors on clearance were within +/-8% for adults and +/-13% for children (95% limits of agreement).
The true relationship between Cl and Cl(1) of (51)Cr-EDTA is given, resulting in a common correction equation applicable for children and adults. The new equation has better mathematical behaviour than quadratic equations on very high values of clearance and takes into account dependence on body size.
（51）铬-乙二胺四乙酸（（51）Cr-EDTA）的总血浆清除率Cl被广泛用作肾小球滤过率（GFR）的一项指标。通常，仅测量血浆浓度曲线的最后部分，并计算单池清除率（斜率-截距清除率）Cl(1)。一般采用经验确定的一般形式为Cl = b×Cl(1) + c×Cl(1)²的二阶多项式，根据测得的Cl(1)来估算Cl。然而，理论分析表明，这种校正方法在高值时会低估Cl。
推导Cl与Cl(1)之间的解析正确关系，并确定儿童和成人的相关参数。
在149名受试者（男/女/儿童：71/46/32）中测定Cl，这些受试者在注射（51）Cr-EDTA后，对完整的血浆浓度曲线进行了4 - 5小时的跟踪（清除率范围：8 - 183 mL/min/1.73 m²）。测量了血浆容积PV以及血浆分数曲线下未用于测定Cl(1)的“缺失”面积a（分钟）。
Cl与Cl(1)之间的真实关系由Cl = Cl(1)/(1 + f×Cl(1))给出，其中f = a/PV。对于男性、女性和儿童，方程f = 0.0032×BSA⁻¹·³均适用（BSA = 以m²为单位的体表面积）。成人清除率的估计误差在±8%以内，儿童在±13%以内（95%一致性界限）。
给出了（51）Cr-EDTA的Cl与Cl(1)之间的真实关系，得出了一个适用于儿童和成人的通用校正方程。新方程在清除率非常高的值时，其数学特性优于二次方程，并且考虑了对身体大小的依赖性。
