11-dehydrothromboxane B2 as a marker of acetylsalicylic acid resistance in patients with stable coronary artery disease

Introduction. Acetylsalicylic acid (ASA, aspirin) resistance is the inability to reduce thromboxane A2 synthesis in platelets and inhibit platelets activation and aggregation while taking ASA. Assessment of urinary 11-dehydrothromboxane B2 (11-dhTxB2) levels is one of the methods to identify aspirin resistance. Our research aimed to investigate whether urinary 11-dhTxB2 levels and other clinical and laboratory parameters are associated with a history of major adverse cardiovascular events (MACE) including myocardial infarction and ischaemic stroke in aspirin-treated patients with stable coronary artery disease. Patients and methods. In a cross-sectional study we investigated 82 patients with stable coronary artery disease who took ASA at doses of 75-150 mg/day. We used the evaluation of the urinary 11-dhTxB2 levels standardized by creatinine as a method to identify aspirin resistance. Statistical analysis was performed using Mann-Whitney U-test, ROC-analysis and multivariable logistic regression. Results. The medians of urinary 11-dehydrothromboxane B2 level in patients with and without MACE were 587.8 (Q1-Q3 512.8-800.3) pg/mg creatinine and 438.3 (Q1-Q3 337.6-577.9) pg/mg creatinine, respectively (p=0.001). The threshold level of urinary 11-dhTxB2, which predicted a high risk of aspirin resistance, was 521.1 pg/mg creatinine, and in 36 (43.9 %) patients the concentration of the 11-dhTxB2 exceeded this level. The regression model characterising the dependence of the presence of a history of MACE was constructed. It included platelet count, urinary levels of 11-dhTxB2 and the presence of type 2 diabetes. Sensitivity and specificity of the model were 55 % and 88.9 %, respectively. Conclusions. The results of the study demonstrate that the antiplatelet effect of aspirin is weaker in stable coronary artery disease patients with a history of MACE than in those without a history of MACE.