Heparin-induced thrombocytopenia without thrombosis: an evidence-based review of current literature

There has been a recent change in the management guidelines for patients with heparin-induced thrombocytopenia with the addition of a recommendation to commence parenteral anticoagulation in patients with isolated HIT without evidence of thrombosis. We assessed the evidence supporting this recommendation, to answer the following questions: in a patient with isolated HIT, should alternative anticoagulation be commenced, what alternative agent should be used, what is the recommended duration of anticoagulation, and when should warfarin be used?

We searched MEDLINE (using keywords "heparin-induced thrombocytopenia", "heparin induced thrombocytopaenia", "HIT" and "HITTS") and PubMed (using MeSH terms "thrombocytopenia" and "heparin") from 1966 to 2006 and selected articles for further assessment according to specified criteria.

We assessed 12 non-randomised studies, five large case series and multiple small case series.

Although patients with isolated HIT are at considerable risk of new thrombosis, there is limited evidence to support or reject the use of non-heparin anticoagulation in this group. Non-randomised, historically controlled trials support the use of lepirudin and argatroban; evidence favouring danaparoid is limited to large case series and one retrospective observational study. Duration of parenteral anticoagulation and warfarin use are guided by consensus opinion alone.