The following two factors must be kept in mind:
Prophylactic therapy, which is indicated in some patients in certain clinical settings, involves the use of heparin (UFH or LMWH) or of one of the new medicines recently introduced for the prevention of DVT in patients undergoing orthopaedic surgery:
In addition to monitoring of platelet counts, which is necessary in patients on heparin, the anticoagulant activity of heparin may be assessed by determination of anti-Xa activity.
Although in theory, laboratory monitoring is not required for administration of rivaroxaban and of dabigatran, tests are available to determine the anti-Xa activity of rivaroxaban; as well as the anti-IIa activity of dabigatran based upon ecarin clotting time (Ecarin Chromogenic Assay - ECA).
Curative treatment of DVT and of PE involves the use of UFH or LMWH (certain types of LMWH are not authorised in the treatment of PE), and more recently, use of fondaparinux (Arixtra®).
If necessary, the anticoagulant activity of fondaparinux may be determined by measuring anti-Xa activity.
Furthermore, vitamin K antagonists should be started on the first day. The target INR is 2.5 (between 2.0 and 3.0).
In patients presenting heparin-induced thrombocytopenia (HIT), alternative therapy is initiated in some countries using danaparoid sodium (Orgaran®), lepirudin (Refludan®) or argatroban. If required, the anticoagulant activity of danaparoid sodium may be measured by determination of anti-Xa activity, while the anticoagulant activity of lepirudin and of argatroban may be assessed by determination of ecarin time (ECA).