Platelet function in essential thrombocythemia and reactive thrombocytosis

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Abstract
Blood of 16 patients with essential thrombocythemia (ET), 9 patients with reactive thrombocytosis (RT) and 13 healthy persons was used for platelet aggregation studies. When the aggregation was induced with adenosine diphosphate (0.01 µM), collagen (0.1 µg/ml) or platelet activating factor (PAF 0.5 µM) the plasma of the patients with ET showed significantly decreased aggregation (35%–44% of the value for the control groups). Independent of inhibitors of platelet aggregation, thrombin (0.05 U/ml) caused similar aggregation in healthy controls and patients with ET; patients with RT showed an increased aggregation. Adrenalin-induced aggregation discriminated best between patients with ET and controls. Adrenalin in concentrations ranging from 0.01 µg/ml to 100 µg/ml caused comparable dose-related amounts of aggregation in healthy controls and patients with RT. Over the whole concentration range, patients with ET showed significantly decreased aggregation (28%–34% of the value for the control groups). This difference proved to be independent of the influence of inhibitors of platelet aggregation. Though concentrations of alpha1-acid glycoprotein never reached inhibitory levels in the plasma of patients with ET (n=12) they were significantly higher compared with those in normal plasma (n=12). Fibrinogen concentrations in plasma of ET-patients (n=12) were in the normal range. Cellular adenosine 3′–5′-cyclic monophosphate concentrations in ET (n=10) are comparable with normal values (n=5). The significance of the results for diagnosis and better pathophysiological understanding of ET is discussed.