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1. NATURAL SCIENCES, 1.6 BIOLOGICAL SCIENCES
Four commercially available Factor Xa (FXa) reagents were evaluated in a fluorogenic anti-FXa assay. The four reagents - of which three were of human origin and the fourth was bovine - were compared in terms of the resulting assay dynamic ranges, lag times, CV and R2 values, sum of squares as well as their sensitivity to unfractionated heparin (UFH) within the therapeutic range of 0-1.2 U mL-1. Based on a balance of performance characteristics, an optimum reagent was selected which had the best combination of all parameters. The best performing serine endopeptidase in the fluorogenic anti-FXa assay was found to be bovine in nature and in liquid form. The resulting assay was very sensitive within the dynamic range of 0-1.2 U mL-1 showing a linear semi-logarithmic dose-response calibration curve with an R2 of 0.99 and CVs%. Of the three human FXa evaluated, the lyophilised human FXa in the absence of stabilizers was demonstrated to be the best performing human FXa reagent. It showed similar behaviour to the bovine reagent in terms of lag time values and dynamic range but with reduced sensitivity. CVs and R2 values were ≤ 2 % and 0.95, respectively, when considering all points in the linear regression fit.
Harris, l. et al (2012) Effects of four commercially available FXa proteins on the fluorogenic anti-FXa assay when monitoring unfractionated heparin. Blood Coagulation & Fibrinolysis, 2012 Jan;23(1):98-103. doi:10.1097/MBC.0b013e32834ddf4d