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The level of heparin-induced antibodies in correlation with the result of the flow cytometric functional assay in the patients with suspected HIT
  1. Elvira Maličev,
  2. Marjeta Maček Kvanka,
  3. Polona Klemenc,
  4. Primož Rožman
  1. Department of Immunohematology, Blood Transfusion Center of Slovenia, Ljubljana, Slovenia
  1. Correspondence to Dr Elvira Maličev, Department of Immunohematology, Blood Transfusion Center of Slovenia, Ljubljana 1000, Slovenia; elvira.malicev{at}


Heparin can induce the formation of antibodies against a heparin complex with a platelet factor 4 (PF4), leading to platelet activation and the development of heparin-induced thrombocytopaenia (HIT). Because screening ELISA does not discriminate between platelet activating and non-activating anti-heparin/PF4 antibodies, each positive result is confirmed by an additional functional assay. We analysed 1004 sera of patients with suspected HIT. Optical density (OD) values of ELISA-positive results were correlated with the risk for a positive result with our functional flow cytometric assay. Only 10.7% were ELISA positive and 59.8% of those were positive with the functional assay. The positive functional assay was found in 23.4% of patients with OD<1.0, in 57.7% with 1.0<OD<2.0 and in 94.1% with OD>2.0. Although our results showed that higher ELISA OD values increasethe possibility of the presence of platelet-activating anti-heparin/PF4 antibodies , there is no need for improving ELISA cut-off value for positive result.

  • heparin-induced thrombocytopenia
  • HIT
  • OD value
  • functional assay
  • platelet activation
  • flow cytometry

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  • Handling editor Mary Frances McMullin

  • Contributors EM: conception and design, collection and assembly of data, data analysis and interpretation, manuscript writing. MMK: performing the literature search, data analysis and interpretation. PK: collection and assembly of data, data analysis and interpretation. PR: final approval of the manuscript.

  • Competing interests None declared.

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