Diagnosis and management of heparin-induced thrombocytopenia

Abstract

Heparin-induced thrombocytopenia (HIT) is a prothrombotic disorder caused by antibodies to platelet factor 4/heparin (PF4/H) complexes. It presents with declining platelet counts 5 to 14 days after heparin administration and results in a predisposition to arterial and venous thrombosis. Establishing the diagnosis of HIT can be extremely challenging. It is essential to conduct a thorough clinical evaluation in addition to laboratory testing to confirm the presence of PF4/H antibodies. Multiple clinical algorithms have been developed to aid the clinician in predicting the likelihood of HIT. Once HIT is recognized, an alternative anticoagulant should be initiated to prevent further complications.

Figure 1. Evolution of the immune response relative to clinical manifestations of HIT

12 patients with HIT and 36 seropositive non-HIT control patients were monitored for PF4/heparin antibodies, thrombocytopenia and thrombosis after orthopedic surgery. HIT patients are indicated by ■, and seropositive non-HIT controls by □. Time course of seroconversions are shown on the x-axis and OD levels between the patients with HIT and the seropositive non-HIT controls (P < 0.05 by nonpaired t test) are shown on the y-axis. At the top of the figure, summary data for 12 HIT patient profiles are shown for 4 key events (first day of antibody detection, beginning of HIT-related platelet count fall, platelet count fall ≥ 50%, and thrombotic event), summarized as median (small black squares within rectangles), interquartile range (open rectangles), and range (ends of thin black lines). Adapted from Warkentin TE, Levine MN, Hirsh J, et al. Heparin-induced thrombocytopenia in patients treated with low-molecular-weight heparin or unfractionated heparin. The New England journal of medicine 1995;332:1330-5.with permission.