Abstract: The present invention provides a method of identifying a coagulation inhibitor in a sample, comprising: a) contacting a first portion of the sample with a substrate and thrombin; b) contacting a second portion of the sample with a substrate and a2M-thrombin (thrombin caged in alpha-2-macroglobulin); c) contacting a third portion of the sample with a substrate and coagulation factor Xa; d) contacting a fourth portion of the sample with a substrate and a2M-Xa (factor Xa caged in alpha-2-macroglobulin); and e) assaying for cleavage of the substrate in (a), (b), (c) and (d) above, wherein cleavage of the substrate in (b) and (d) and no cleavage in (a) and (c) identifies heparin in the sample; cleavage of the substrate in (a), (b) and (d) and no cleavage in (c) identifies low molecular weight heparin in the sample; cleavage of the substrate in (a) and (b) and no cleavage in (c) and (d) identifies rivaroxaban in the sample, and cleavage of the substrate in (c) and (d) and no cleavage in (a) and (b) identifies dabig