Obstacles in the diagnostics and therapy of heparin-induced thrombocytopenia

Abstract

An immune-mediated, severe, acquired prothrombotic disorder, heparin-induced thrombocytopenia type II (HIT II) occurs in 0.5-5% of patients exposed to unfractionated heparin longer than 5-7 days. Arterial and venous thromboses are induced by HIT II in about 35-50% of patients. Typical death rate for HIT is about 29%, while 21% of HIT patients result in amputation of a limb. The trend towards the occurrence of HIT due to the administration of low molecular weight heparins (LMWH) taking ever conspicuous place in the standard venous thromboembolism (VTE) prophylaxis has been more frequently observed recently. It is considered that LMWH may cause HIT II in about 0.25-1%. The need for further modification of HIPA assays with LMWH has been imposed in the HIT laboratory diagnostics, heretofore overburdened with complexity. There are several constantly opposing problems arising in HIT laboratory diagnostics, one of which is that in a certain number of patients immunologic assays detect nonpathogenic antibodies (mainly IgM or IgA heparin-PF4 antibodies) while, on the other hand, the occurrence of HIT pathogenetically mediated by minor antigens (neutrophil-activating peptide 2 or interleukin 8) may be neglected in certain cases. The following factors play an important role in the interpretation of each laboratory HIT assays performed: 1. correlation with HIT clinical probability test, the best known of which is 4T'score, 2. the interpretation of the laboratory findings dependent on the time of the thrombocytopenia onset, as well as 3. the sensitivity and specificity of each test respectively. The HIT diagnostics in the presence of other comorbid states which may also induce thrombocytopenia, more precisely known as pseudo HIT (cancer, sepsis, disseminated intravascular coagulation, pulmonary embolism, antiphospholipid syndrome, etc), represents a specific clinical problem.

Prevention of thromboembolism in orthopedic surgery: Application of rivaroxaban in arthroplastic procedures

“…Kao jedna od glavnih negativnih posledica primene heparinskih preparata ističe se heparinom uzrokovana trombocitopenija 51 . Kao što je navedeno, incidenca heparinske trombocitopenije je 3-5% kod primene UFH u ortopedskoj hirurgiji, što je kod LMWH sniženo na 0-0,9% 52,53 .…”

Prevention of venous thromboembolism with rivaroxaban and apixaban in orthopedic surgery

“…Like unfractionated heparin (UFH) low molecular weight heparins (LMWH) reduce the risk of VTE at least 60% compared to patients without thromboprophylaxis, but are not convenient for outpatients as they require subcutaneous administration [5,6]. The incidence of heparin thrombocytopenia (HIT), as a serious adverse effect of the applied anticoagulant therapy, is approximately 3-5% in patients treated with UFH in orthopedic surgery and about 0.9% in patients treated with LMWH [7][8][9][10][11][12].…”