[Aspirin resistance in patients taking small dose of aspirin]

To investigate the phenomenon and influencing factors of aspirin resistance (AR) in patients taking small dose of aspirin.

Three hundred and twenty-eight patients with stable cardiac and cerebral vascular diseases, diabetes mellitus, et al taking aspirin 100 mg/d for > or =14 days, and then their blood samples were collected for determination of optical platelet aggregation index using arachidonic acid (AA) and adenosine diphosphate (ADP). AR was defined as a state in which aggregation of > or =20% with AA and that > or =70% with ADP was found. Aspirin semi-resistance (ASR) was defined as meeting one of the above criteria. If both above criteria were not met, the condition was defined as aspirin sensitive. The difference in clinical characteristics among the groups and independent risk factors associated with AR and ASR were analyzed.

Of 328 patients, 4.9% were AR, 27.4% were ASR. Among AR+ASR group, female, elderly, diabetic and hypertensive patients were predominant, but less common in smokers. Logistic regression analysis showed that diabetes mellitus was an independent risk factor of AR and ASR [odds ratio (OR)=0.953, 95% confidence interval (CI) 0.323-0.876, P=0.013], and hypertension was independently associated with AR and ASR (OR=0.610, 95%CI 0.376-0.991, P=0.046). The risk of AR and ASR was increased in non-smokers (OR=2.231, 95%CI 1.182-4.210, P=0.013).

The incidence rate of AR in patients taking small dose of aspirin was 4.9%. Diabetes mellitus and hypertension are relative risk factors of AR and ASR. The risk of AR and ASR in the no-smoking patients is increased.