The use of ecarin chromogenic assay and prothrombinase induced clotting time in the monitoring of lepirudin for the treatment of heparin-induced thrombocytopenia

Lepirudin (r-hirudin) is one of the two alternative anticoagulants licensed to treat patients with heparin-induced thrombocytopenia (HIT). Manufacturer's guidelines state that lepirudin should be monitored using the activated partial thromboplastin time (APTT) ratio. However, several studies have demonstrated a plateau effect of higher concentrations of lepirudin on APTT ratios and variable results when comparing different APTT reagents. This study compares APTT ratios (using two different APTT reagents) with two other commercially available methods for directly quantifying plasma lepirudin levels: ecarin chromogenic assay and prothrombinase-induced clotting time in 95 samples from five patients receiving lepirudin anticoagulation for HIT.