Turk Kardiyol Dern Ars. 2010; 38(4): 239-243

Platelet function analysis with two different doses of aspirin

Alp Aydınalp, İlyas Atar, Cihan Altın, Öykü Gülmez, Aslı Atar, Sadık Açıkel, Hüseyin Bozbaş, Aylin Yıldırır, Haldun Müderrisoğlu
Department of Cardiology Baskent University Faculty of Medicine, Ankara, Turkey

OBJECTIVES
We aimed to compare the level of platelet inhibition using the platelet function analyzer (PFA)-100 in patients receiving low and medium doses of aspirin.

STUDY DESIGN
On a prospective basis, 159 cardiology outpatients (83 men, 76 women; mean age 60.9±9.9 years) taking 100 mg/day or 300 mg/day aspirin at least for the previous 15 days were included. Of these, 79 patients (50%) were on 100 mg and 80 patients (50.3%) were on 300 mg aspirin treatment. Blood samples were collected between 09: 30 and 11: 00 hours in the morning. Platelet reactivity was measured with the PFA-100 system. Incomplete platelet inhibition was defined as a normal collagen/epinephrine closure time (<165 sec) despite aspirin treatment.

RESULTS
Baseline clinical and laboratory characteristics of the patient groups taking 100 mg or 300 mg aspirin were similar. The overall prevalence of incomplete platelet inhibition was 22% (35 patients). The prevalence of incomplete platelet inhibition was significantly higher in patients treated with 100 mg of aspirin (n=24/79, 30.4%) compared with those treated with 300 mg of aspirin (n=11/80, 13.8%) (p=0.013). In univariate analysis, female sex (p=0.002) and aspirin dose (p=0.013) were significantly correlated with incomplete platelet inhibition. In multivariate analysis, female sex (OR: 0.99; 95% CI 0.9913-0.9994; p=0.025) and aspirin dose (OR: 3.38; 95% CI 1.4774-7.7469; p=0.003) were found as independent factors predictive of incomplete platelet inhibition.

CONCLUSION
Our findings suggest that treatment with higher doses of aspirin can reduce incomplete platelet inhibition especially in female patients.

Keywords: Aspirin/therapeutic use, blood platelets/drug effects, dose-response relationship, drug; drug resistance; platelet aggregation/drug effects; platelet function tests/methods

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