THE EFFECT OF A HEPARIN REMOVAL FILTER ON PLATELET-AGGREGATION STUDIES IN HEPARIN-INDUCED THROMBOCYTOPENIA

Patients having a heparin-associated platelet antibody who are receivi ng heparin at the time of testing for heparin-induced thrombocytopenia (HIT) by platelet aggregometry may exhibit aggregation in the negativ e control channel. Filtering plasma to remove the heparin may produce a nonaggregating negative control channel. The effect of the Pall Hepc hek (Pall Biomedical, East Hills, NY) heparin removal filter on platel et aggregation studies was evaluated. Samples were studied from 10 pat ients with clinically established HIT, The pre-filtration platelet agg regation studies were unequivocally positive for heparin antibody. The remainder of each sample was filtered and the aggregation studies wer e repeated. Of the four patients on IV heparin, only one remained posi tive post-filtration. Of the six patients receiving subcutaneous hepar in or flushes, one remained strongly positive, one was borderline, and four became negative. Pall Hepchek heparin filtration unpredictably a lters the results of platelet aggregation studies, and should not be u sed routinely to remove heparin in the presence of aggregation in the negative control.