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The Advantages and Limitations of Impedance Aggregometry in Detection of Heparin-Induced Thrombocytopenia by L. Slavik, G. Svobodova, J. Ulehlova, V. Krcova, A. Hlusi, J. Prochazkova, M. Kaletova, Y. Hrckova, K. Indrak

Background: Heparin-induced thrombocytopenia (HIT) represents a serious complication of heparin treatment. IgG antibodies binding platelet factor 4 (PF4) and heparin trigger the clinical manifestations of HIT. However, only a portion of the antibodies have the ability to activate platelets, and these can be identified by a platelet aggregation test (functional testing). Current methods HIPA and SRA are time-consuming and difficult if HIT is clinically suspected; therefore, numerous new methods have recently been developed.
Methods: To determine HIT, impedance aggregometry using the Multiplate® analyzer (MEA) as heparin-induced aggregation techniques and the Technozym HIT Ig ELISA test were used. The MEA method uses sensitization of donor platelets with patient plasma in the presence of heparin at a concentration of 0.5 IU/mL. The results were compared with the ELISA test.
Results: We examined 190 patients at clinically intermediate and higher risk of HIT according to the 4T score. All samples were examined by the ELISA test and MEA, with positive samples being further confirmed by high-concentration heparin. The methodology was modified with respect to the dilution for high positive samples and assessment has been extended to an index of inhibition.
Conclusions: In the studied group, we demonstrated that MEA has sufficient sensitivity and higher specificity. In the group of patients, 10.0% showed positive results by MEA as compared with 7.3% determined by ELISA. Unlike the ELISA methods of the same quality, MEA is more suitable for detecting platelet-activating HIT antibodies in practice.

DOI: 10.7754/Clin.Lab.2013.130740