Hyperaggregation effect in idiopathic thrombocytopenia and multiple transfused patients.

A new technique for detecting platelet antibodies was investigated. The serum from patients having platelet antibodies was added to normal group O compatible pooled platelet-rich plasma. Platelet aggregation induced by adrenaline and adenosine diphosphate (ADP) was significantly increased as compared to the identical platelet-rich plasma without serum. The platelet-rich plasma with serum added did not aggregate spontaneously. When an alpha-adrenergic blocking agent (tolazoline) was added, the primary wave of aggregation induced by adrenaline was equally reversed with platelet-rich plasma, with or without serum. Although platelet antibodies by themselves did not agglutinate platelets in our test system, it is probable that platelet antibodies interact with platelets and potentiate their ability to aggregate. It is suggested that the platelet aggregometer is a useful tool for the detection of platelet antibodies in vitro.