Observational Studies

The first published case of fondaparinux use in a patient with HIT was by Dr. Elbio D'Amico et al. (2003). A patient with paroxysmal nocturnal hemo-globinuria and Budd-Chiari syndrome developed HIT following administration of LMWH (dalteparin 5000IU sc q12h). The patient experienced spontaneous platelet count recovery, and received thrombolytic therapy. While receiving prophylactic doses of fondaparinux, the platelet count remained unchanged and the patient was transitioned uneventfully to oral anticoagulant therapy.

There are now at least six published reports (D'Amico et al., 2003; D'Angelo et al., 2006; Haase et al., 2005; Harenberg et al., 2004; Kovacs, 2005; Parody et al., 2003), three abstracts (Boshkov et al., 2004; Grabowski and Bussel, 2006; Piovella et al., 2006) and one unpublished case series describing the use of fondaparinux to treat HIT (Table 3). The case series involved 38 patients with HIT who were treated with fondaparinux at the Massachusetts General Hospital (MGH) between January 1, 2002, and August 1, 2004 (Table 3). This series represents two cohorts of patients treated either with fondaparinux after initial treatment with a DTI (n = 17) or receiving fondaparinux for the initial treatment of HIT (n = 21). Platelet count recovery data from the MGH series are presented in Figure 3, representing normalized, daily platelet counts of patients who received fondaparinux during the acute thrombocytopenic phase. The platelet recovery and the low incidence of thromboses in the treated cohorts (2/38) are consistent with the conclusion that there is no clinical cross-reactivity between fondaparinux and HIT antibodies. None of the studies reported prolonged or recurrent thrombocytopenia during fondaparinux treatment. An important limitation of these studies is that relatively few patients underwent functional testing using platelet activation assays that have relatively high diagnostic specificity for HIT (see Chapter 10).

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