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Current insights into the laboratory diagnosis of HIT
Author(s) -
Bakchoul T.,
Zöllner H.,
Greinacher A.
Publication year - 2014
Publication title -
international journal of laboratory hematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.705
H-Index - 55
eISSN - 1751-553X
pISSN - 1751-5521
DOI - 10.1111/ijlh.12236
Subject(s) - heparin induced thrombocytopenia , platelet factor 4 , heparin , medicine , antibody , platelet activation , platelet , immunology , thrombosis
Summary Heparin‐induced thrombocytopenia (HIT) is an adverse drug reaction and prothrombotic disorder caused by immunization against platelet factor 4 (PF4) after complex formation with heparin or other polyanions. After antibody binding to PF4/heparin complexes, HIT antibodies are capable of intravascular platelet activation by cross‐linking Fc gamma receptor IIa (FcγRIIa) on the platelet surface leading to a platelet count decrease and/or thrombosis. In contrast to most other immune‐mediated disorders, the currently available laboratory tests for anti‐PF4/heparin antibodies show a high sensitivity also for clinically irrelevant antibodies. This makes the diagnosis of HIT challenging and bears the risk to substantially overdiagnose HIT. The strength of the antigen assays for HIT is in ruling out HIT when the test is negative. Functional assays have a higher specificity for clinically relevant antibodies, but they are restricted to specialized laboratories. Currently, a Bayesian approach combining the clinical likelihood estimation for HIT with laboratory tests is the most appropriate approach to diagnose HIT. In this review, we give an overview on currently available diagnostic procedures and discuss their limitations.