In vivo platelet activation in beta-thalassemia major reflected by increased platelet-thromboxane urinary metabolites.

Increased frequency of thromboembolic events has been recently observed in patients with beta-thalassemia major (TM). Platelet function anomalies including impaired aggregation, increased circulating aggregates, and our finding of shortened platelet survival indicate that platelets may be involved in the hypercoagulability in thalassemia. Consequently, we used a technique based on thin layer chromatography purification and enzyme immunoassay to measure urinary metabolites of thromboxane A2 (TXA2) and prostacyclin (PGI2) in nine splenectomized patients with beta-TM regularly transfused, five non-splenectomized patients with beta-thalassemia intermedia (TI), and 20 healthy individuals. A significant 4- to 10-fold increase was observed in the urinary excretion of 2,3-dinor-TXB2, 11-dehydro-TXB2 and 2,3-dinor-6-keto-PGF1 alpha in patients with TM and TI as compared with healthy controls. No significant differences were found in the concentrations of these metabolites between TM and TI patients. Six TM patients received a very low dose of aspirin (20 mg/day) for 7 days. A significant decrease was observed in the urinary concentrations of 2,3-dinor-TXB2 and 11-dehydro-TXB2 derived from platelets. However, the levels of urinary 2,3-dinor-6-keto-PGF1 alpha reflecting vascular production and TXB2 and 6-keto-PGF1 alpha originating from the kidney were not significantly changed. These results are consistent with those of increased in vivo production of TXA2 because of endogenous platelet activation.