Heparin induced thrombocytopenia. Variable platelet-rich plasma reactivity to heparin dependent platelet aggregating...

The heparin dependent platelet aggregating factor in the serum from an individual with heparin induced thrombocytopenia exhibited reactivity with only 50% of an extensive panel of normal platelet rich plasmas, and this variability was independent of the platelet rich plasma platelet Factor 4 content. Individual sera of 3 other patients with heparin induced thrombocytopenia showed considerable variation in the lag phase and rate of platelet aggregation when tested with different normal platelet rich plasma preparations. These findings suggest that in the appropriate clinical setting the documentation of heparin dependent platelet aggregating factor should employ a panel of platelet rich plasmas if the initial screen is negative.