Current possibilities of laboratory diagnosis heparin-induced trombocytopenia


Authors: L. Slavík;  G. Svobodová;  J. Úlehlová;  V. Krčová;  A. Hluší;  J. Procházková
Authors‘ workplace: Hemato-onkologická klinika LF UP a FN Olomouc
Published in: Transfuze Hematol. dnes,18, 2012, No. 2, p. 76-80.
Category: Comprehensive Reports, Original Papers, Case Reports

Overview

Heparin-induced thrombocytopenia (HIT) represents a serious complication of heparin use. 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 – heparin-induced platelet aggregation (HIPA) and 14C-serotonin release assay (SRA) – are time-consuming and difficult if HIT is clinically suspected; therefore, numerous new methods have been developed recently. To determine HIT, impedance aggregometry using the Multiplate® analyzer (Verum Diagnostika, Munich, Germany) (MEA) as heparin-induced aggregation techniques and the Technozym HIT Ig ELISA test (Technoclone GmbH, Vienna, Austria) 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. MEA was performed in 300 μL of citrated whole blood with donor platelets, 150 μL of heparin (final concentration of 0.5; 100 IU/mL) and 150 μL of platelet-poor plasma (PPP) from the patient. Changes in aggregation were monitored for 20 minutes. The ELISA test results were evaluated as negative for OD <0.500 and positive for OD> 0.500 according to the manufacturer’s diagnostic setup. We examined 65 patients at a 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. In the studied group, we demonstrated that MEA has sufficient sensitivity and higher specificity. In the group of patients, there were 7.8% of positive results found by MEA as compared with 10.9% determined by ELISA. Unlike the ELISA methods of the same quality, MEA is more suitable for detecting platelet-activating HIT antibodies in practice.

Key words:
heparin-induced thrombocytopenia, functional test for HIT, ELISA determination of HIT


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Labels
Haematology Internal medicine Clinical oncology

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