A method of identifying a non-anticoagulant sulfated polysaccharide (NASP) which is capable of enhancing blood coagulation in dependence of FXI, the method comprising: a) combining a blood or plasma sample having activation competent FXI with a sulfated polysaccharide and measuring the clotting or thrombin generation parameters of the blood or plasma sample; b) combining a corresponding blood or plasma sample deficient In activation competent FXI with a sulfated polysaccharide and measuring the clotting or thrombin generation parameters of the blood or plasma sample and c) comparing the clotting or thrombin generation parameters of the blood or plasma samples as determined in steps (a) and (b) with each other.