cirrhosis and ascites: a comparison of three models

Cr-EDTA was given to 13 patients withcirrhosis and ascites. Up to16 blood samplesweredrawn attime points ranging from 5 to 1440min following injection.The concentration data prior to 120min were used asreference data. Early time concentration values, estimatedby fitting exponential, linear-log, and negative-powerfunctions of time to the time samples at 120, 180, and240min, were then compared with reference data. The AUCwas calculated for each patient using the exponential,Brochner-Mortensen-corrected exponential, and linear-logfunctions, and these values were compared.Results The withheld, observed plasma concentrationswere (a) most accurately estimated by linear-log functions(Wilcoxon P=0.4548), (b) significantly underestimated byexponential functions (Wilcoxon P=0.0002), and (c)significantly overestimated by negative-power functions(Wilcoxon P=0.0034). The relative errors when ranked frombest to worst were those for the linear-log (12.0%, 9.0%),exponential (22.9%, 14.2%), and negative-power (31.9%,48.4%) functions of time, respectively (median, interquartilerange). For each patient, the values for AUC calculated bythe exponential function differed significantly(range=3.4–15.3%, median=8.3%) from those calculatedby the corrected Brochner-Mortensen exponential, as to alesser extent did those values calculated using linear-logfunctions (range=0.4–8.0%, median=3.0%).Conclusion In patients with cirrhosis, linear-log functionswere significantly more accurate than exponential or powerfunctions in estimating early time plasma concentrations(<120min). However, the improved linear-log early timeplasma concentration model does not provide as muchcorrection to the total AUC as does the corrected Brochner-Mortensen exponential method. This is likely because of thelarge contribution of late time data to the AUC, and futurework is suggested to explore the late time fit problem. NuclMed Commun 36:392–397 Copyright © 2015Wolters Kluwer Health, Inc. All rights reserved.