• E Lindhoff-Last, P Eichler, M Stein, J Plagemann, F Gerdsen, R Wagner, A M Ehrly, and R Bauersachs.
• Medical Department of Internal Medicine, University Hospital Frankfurt, Frankfurt, Germany. Lindhoff-Last@em.uni-frankfurt.de
• Thromb. Res. 2000 Mar 15; 97 (6): 387-93.

AbstractThe heparin-platelet factor 4-antibody assay, polyanion-platelet factor 4-antibody assay and heparin-induced platelet activation test are used for laboratory diagnosis of the immune form of heparin-induced thrombocytopenia. Fifty consecutive patients receiving heparin treatment for more than 5 days after vascular surgery were prospectively screened for heparin-induced thrombocytopenia antibodies, thrombocytopenia (daily platelet counts), deep-vein thrombosis (color-coded duplex sonography), and arterial reocclusion (clinical assessment). None of the patients developed thrombocytopenia or thrombosis in association with formation of heparin-induced thrombocytopenia antibodies. Despite the absence of clinical evidence of heparin-induced thrombocytopenia, many patients formed heparin-induced thrombocytopenia antibodies: 34% of the patients were positive in the heparin-platelet factor 4-antibody assay, 28% in the polyanion-platelet factor 4-antibody assay, 14% in the heparin-induced platelet activation test, and 54% with any of these tests. Patients predominantly developed IgM (24%) and IgA antibodies (16%), whereas IgG antibodies were found in 12% of patients. Whereas the majority of patients with positive ELISA assays had IgM and IgA antibodies, patients with a positive functional assay (heparin-induced platelet activation test) predominantly had IgG antibodies. We conclude that a high percentage of patients develop heparin-induced antibodies after vascular surgery without any clinical symptoms of heparin-induced thrombocytopenia. None of the assays therefore is predictive of the clinical manifestation of heparin-induced thrombocytopenia in asymptomatic patients. Therefore, the diagnostic specificity of both antigen and activation assays for heparin-induced thrombocytopenia appears to be relatively low in the vascular surgery patient population.

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