Platelet Adrenergic Receptor Dysfunction Is Associated with Both Aggregation and Adhesion Defects: Application of the Cone and Plate(let) Analyzer for Diagnosis and Monitoring of the Response to DDAVP Therapy.

Diagnosis of platelet function disorders is based on the nature of bleeding symptoms, a positive family history and abnormal laboratory tests. However, currently available methods are time and labour consuming and lack sensitivity and specificity. In the present study we evaluated the performance of the Cone and Plate (let) analyzer (CPA) for screening patients with a suspected platelet function disorder and for monitoring therapy.

Consecutive patients presenting with spontaneous or post surgical bleeding were studied. All patients underwent primary and secondary hemostasis evaluation including CPA testing. In this test a volume of 200μL of citrated whole blood is placed onto polystyrene wells and submitted to flow (shear rate of 1800 sec. ⁻¹) by a Teflon cone for 2 minutes. The resulting platelet deposition is then read by an image analyzer and expressed as % of the well surface covered ( SC, %) with adhered platelets and as the average size (AS, μm²)of platelet aggregates. Patients with a platelet function disorder were further tested with a modified CPA test in which blood samples are pre-incubated (1 min.) with a sub-optimal concentration of an agonist prior to subjecting the sample to the regular CPA test. Response of platelets to the agonist leads to agglutination and micro aggregates formation in the suspension phase of the test tube with consequent decline in platelet adhesion.

165 consecutive bleeding patients were evaluated and compared to 54 healthy controls. We diagnosed 51 patients as suffering from a platelet function disorder, of whom 8 patients (GTA – 7, BSS – 1) were excluded. The remaining 43 patients presented complete unresponsiveness to epinephrine in repeated platelet aggregation tests while all other coagulation, liver and renal function tests were normal and similar to healthy controls. In the CPA test these 43 patients had a significantly lower SC values compared to the other patients or to healthy controls. To further explore the CPA’s diagnostic capability 6 patients were compared to 16 randomly chosen controls using the modified CPA test. Whereas SC declined significantly by 73% in healthy controls after pre-incubation with epinephrine a non significant decline of only 15% was noted in patients with platelet adrenergic receptor dysfunction (table). Seventeen patients with platelet adrenergic receptor dysfunction underwent surgery. Following pre-surgical administration of DDAVP SC values followed closely and the VWF:RCo levels whereas the response to epinephrine in routine aggregometry did not change. All patients underwent successful operations without excessive bleeding.

Our data suggest that patients with adrenergic receptor dysfunction suffer from a combined aggregation and adhesion platelet defects. The CPA test was found useful for screening both adhesion and aggregation of platelet disorders including adrenergic receptor dysfunction as well as for monitoring DDAVP therapy in these patients.