Effects of four commercially available factor Xa proteins on the fluorogenic anti-factor Xa assay when monitoring unfractionated heparin

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, coefficient of variation and R ² values, as well as their sensitivity to unfractionated heparin within the therapeutic range of 0-1.2U/ml. Similar performance of reagents in the fluorogenic anti-FXa assay was observed independent of the source of the reagent or its physical state, which may assist in the standardization of coagulation assays in clinical settings.