Abstract:
Background: Aspirin resistance is considered to be an enigma and the data available on aspirin resistance is
scarce. This study was initiated to prospectively evaluate the prevalence of aspirin resistance in patients with
stable coronary artery disease by using an established method of optical platelet aggregation.
Methods and Results: We studied 50 patients who were on 150 mg of aspirin for the previous 7 days. Fasting
blood samples were assessed using optical platelet aggregation (Chronolog Corp, USA). The mean platelet
aggregation with 10 μm of adenosine diphosphate in our patient group was 49.42 ± 23.29% and with 0.5 mg/
ml of arachidonic acid it was 13.58 ± 21.40%. Aspirin resistance was defined as a mean aggregation of
≥70% with 10 μm of adenosine diphosphate and a mean aggregation of ≥ 20% with 0.5 mg/ml of arachidonic
acid. Aspirin semi responders were defined as those meeting only one of the criteria. Based on these criteria,
2.08% patients were found to be aspirin-resistant, 39.58% were aspirin semi responders and 58.33% were
aspirin responders. Females tended to be more aspirin semi responsive (p = 0.08). All other parameters tested,
namely, age, smoking, diabetes mellitus, hypertension, obesity, lipids, hemoglobin, platelet count, ejection fraction
and drug intake did not show any statistically significant difference among the groups. Thus, in our group
41.66% patients showed inadequate response to aspirin.
Conclusions: This study shows that aspirin resistance and aspirin semi responsiveness do occur in the Indian
patients and there are no reliable clinical predictors for this condition. The diagnosis therefore relies primarily
on laboratory tests.
