Heparin induced thrombocytopenia and thrombosis in a tertiary care hospital.

UNLABELLED: Heparin-induced thrombocytopenia (HIT) results from development of an antibody to a complex of heparin and platelet factor 4 (PF4) resulting in thrombocytopenia and a prothrombotic state with serious clinical consequences. The diagnosis depends on a combination of both the clinical presentation and laboratory detection of an appropriate antibody.
OBJECTIVE: To determine the frequency, clinical characteristics and laboratory correlates of HIT in a tertiary care hospital.
METHODS: A retrospective review of all case of HIT over a thirty month period in a tertiary care hospital was conducted.
RESULTS: HIT was diagnosed in 136 patients including 114/28,091 (0.48%) of those receiving only unfractionated heparin, 22/6,559 (0.33%) of those that received both unfractionated and low-molecular-weight heparin (LMWH) and in 2/2498 (0.08%) of those receiving only LMWH (P=0.02 compared to those receiving only unfractionated heparin). HIT occurred in 62/16,939 patients (0.39%) of patients receiving subcutaneous (SC) heparin or LMWH compared to 69/11,152 (0.62%) of patients receiving intravenous (IV) therapy (P=0.003). Of all patients with exposure to heparin products, 41/34,650 (0.1%) developed symptomatic thrombosis. The optical density (OD) of the ELISA was significantly higher in patients with HIT and thrombosis (1.2 +/- 0.8) compared to those without thrombosis (0.9 +/- 0.6, P=0.03).
CONCLUSION: HIT develops in approximately 0.4% of all patients exposed to heparin at a tertiary care hospital but is significantly less frequent in those treated with LMWH only than in those who receive unfractionated heparin. A higher antibody titer is associated with the development of thrombosis. The occurrence of HIT could be decreased by reducing exposure to unfractionated heparin, and the diagnosis could be improved by reporting the OD of the ELISA test result.