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Semin Thromb Hemost 2012; 38(02): 135-143
DOI: 10.1055/s-0032-1301411
Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Evaluating Heparin-Induced Thrombocytopenia: The Old and the New

Chee Wee Tan
1   Northern Blood Research Centre, Kolling Institute, University of Sydney, Sydney, Australia
2   Department of Haematology and Transfusion Medicine, Royal North Shore Hospital, St Leonards, NSW 2065, Australia
,
Christopher Morice Ward
1   Northern Blood Research Centre, Kolling Institute, University of Sydney, Sydney, Australia
2   Department of Haematology and Transfusion Medicine, Royal North Shore Hospital, St Leonards, NSW 2065, Australia
,
Marie-Christine Morel-Kopp
1   Northern Blood Research Centre, Kolling Institute, University of Sydney, Sydney, Australia
2   Department of Haematology and Transfusion Medicine, Royal North Shore Hospital, St Leonards, NSW 2065, Australia
› Author Affiliations
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Publication History

Publication Date:
08 February 2012 (online)

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Abstract

Heparin-induced thrombocytopenia (HIT) is a rare but potentially serious complication of heparin use. Prompt diagnosis is crucial and requires the integration of clinical assessment and laboratory testing. Pretest clinical scoring systems (i.e., 4 Ts) have been established. Immunoassays can detect the presence of antibodies directed toward heparin-platelet factor 4 (H-PF4) complexes, but provide no information about their ability to activate platelets. A low clinical score, when combined with a negative immunoassay result obviates the need for further testing. However, immunoassays and 4 Ts scores have only modest specificity. Functional testing (serotonin release assay or heparin-induced platelet activation) remain important in confirming the presence of pathogenic H-PF4 antibodies, but are technically demanding to perform and limited in guiding clinical decisions in the acute setting. This review evaluates current immuno- and functional assays available in the laboratory diagnosis of HIT, and describes recent attempts to improve the specificity of enzyme immunoassays, including adopting an immunoglobulin G-specific assay and raising the optical density value cutoff for a positive result. The importance of donor selection and newer functional assays, including flow cytometry-based assays, are also discussed. A current approach to integrating clinical scoring, immunoassays, and functional testing for HIT is also outlined.

Keywords

heparin-induced thrombocytopenia - heparin-platelet factor 4 enzyme immunoassays - heparin-platelet factor 4 particle-gel immunoassay - functional assays - heparin-induced thrombocytopenia - clinical scoring
 

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