Simplified algorithms for the estimation of Tc-99(m)-MAG3 clearance

The aim of this study was to evaluate two formulae allowing the determinati on of MAG3 clearance by means of a single blood sample, namely Bubeck's for mula and Russell's formula. As a first step, a simulation study was perform ed with the two single-sample algorithms to predict MAG3 clearance as a fun ction of plasma concentration, using various times for blood sampling; and various body surface areas. As a second step, a validation study on 47 adul t patients with varying renal function allowed a clinical comparison betwee n the reference technique, namely the multiple blood sample technique, and the two simplified techniques. The simplified algorithms were calculated us ing the fitted value at 44 min. In the simulation study, whatever the time of blood sampling or the level of correction introduced for body surface ar ea, the results obtained by means of Bubeck's algorithm diverged significan tly from those of Russell's algorithm, for low clearance values as well as for high clearance values. The curve of the differences between the two met hods had a typical boomerang shape. In the clinical study, the difference b etween Russell's algorithm and the reference method was generally within 20 ml.min(-1), with no systematic bias; with Bubeck's algorithm there was a m arked underestimation, both in the low and high clearance ranges. We sugges t Russell's single-sample method is the method of choice. ((C) 2000 Lippinc ott Williams & Wilkins).