A review of the monitoring of argatroban by anti-IIa methods, ecarin assays, point-of-care testing methods and specialized drug quantification methods for patients with heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is caused by anti-PF4/heparin IgG antibodies stimulating platelet activation, causing thrombocytopenia and thrombosis. Classical HIT occurs due to exposure to heparin, whereas autoimmune HIT occurs via heparin-independent platelet activation (caused by anti-PF4/polyanion IgG) and relates to a platelet count fall that begins or persists without heparin. Treatment for HIT requires transitioning patients onto alternative anticoagulation. The direct thrombin inhibitor argatroban has been licensed for use in patients with HIT and was recommended to be monitored by the activated partial thromboplastin time (aPTT). Recent European guidelines have suggested that monitoring drug concentrations is more suitable and will reduce the risk of under or over anticoagulating patients. This review will discuss anti-IIa and ecarin-based laboratory methods for determining plasma argatroban concentrations, the use of viscoelastography methods and other point-of-care testing (POCT) methods in whole blood. The use of more specialised tests based on high-performance liquid chromatography will also be discussed, comparing these methods with aPTT.