Patent ID: 7923217

Claim:
A method for determining the antithrombin III (AT) content in a sample that may contain one or more pharmaceutical compounds that inhibit thrombin, the method comprising: (a) providing a reaction mixture by contacting the sample with a first reagent R1 comprising thrombin, under conditions wherein the thrombin essentially does not interact with AT but interacts with the one or more pharmaceutical compounds that inhibit thrombin, if present, (b) adding to the reaction mixture a second reagent R2 comprising a chromogenic substrate which is a peptide substrate for thrombin, and determining the amount of thrombin activity in the reaction mixture, (c) changing the conditions of the reaction mixture by adding to the reaction mixture a third reagent R3 comprising heparin such that thrombin interacts with AT, (d) conducting a second determination of the thrombin activity in the reaction mixture, wherein the determination comprises using the reagent R2, (e) determining the difference between the first and second determinations of thrombin activity, and (f) determining the AT content of said sample from said difference determined in step (e).