Background: Aspirin is commonly used as antithrombotic agent to prevent primary and secondary cardiovascular
events. A proportion of aspirin-treated patients was found to be resistant to its antithrombotic effect. This proportion
varies widely in different studies ranging from 0 to 60% of aspirin treated patients.
Aim: To determine the prevalence of aspirin resistance among patients with stable ischemic heart disease through
measurement of 11-dehydrothromboxane B2 in urine.
Methods: The level of 11-dehydroTXB2 in urine was measured by ELISA method using commercial kits (Wuhan
company, China). Fifty three patients with stable ischemic heart disease (IHD) on 100 mg aspirin daily for not less
than one month (recruited from the Teaching Hospital Consultation Clinics and 50 apparently healthy volunteers
were involved in this study). Urine samples were taken in the morning from patients and volunteers and freezed until
analysis for 11-dehydroTXB2 and urinary creatinine. Blood samples were used for measurement of different blood
indices, lipid profile and glucose level. Absolute values of 11-dehydroTXB2 in pg/ml of urine and normalized values in
pg/mg creatinine were used for analysis. Two cutoff points reported in the literature to be associated with increased
incidence of clinical events were used to determine the prevalence of aspirin resistance.
Results: The level of 11-dehydroTXB2 in urine of normal subjects was 60.26±66.3 pg/mg creatinine, ranging from
11 to 379 pg/mg creatinine, while the level in patients with stable IHD on aspirin treatment 100mg orally, was 63.34
± 61.27 pg/mg creatinine, ranging from 5 to 316 pg/mg creatinine. There was no statistically significant difference
between males and females in the two groups. Associated diseases such as diabetes and hypertension, cholesterol level
and different blood indices do not seem to be associated with altered levels of 11-dehydroTXB2. The prevalence of
aspirin resistance in the present study was ranging from 1.8% to 7.5% for patients with stable ischemic heart disease.
Conclusion: the prevalence of aspirin resistance was ranging from 1.8% to 7.5% in patients with stable IHD. The
level of 11-dehydroTXB2 in urine of apparently healthy subjects and patients with stable IHD on aspirin treatment
100mg orally was similar