To determine the prevalence of aspirin resistance in patients taking this drug and to test if resistance is related to haemostatic, inflammatory and lipidic variables.
Platelet function measured with PFA-100 was studied in 268 patients (185 men) with stable coronary disease who took aspirin (100 to 300 mg/day). Aspirin resistance was defined when epinephrine closure time < 174 s. Results of lipoprotein(a) are expressed in median (interquartile range).
Aspirin resistance was found in 16 % of cases. Patients with aspirin resistance had higher levels of Apolipoprotein B (109.27 ± 27.65 vs 100.92 ± 23.77 mg/dl; p < 0.05), lipoprotein(a) [20.37 (4.83–36.72) vs 10.02 (1.88–25.41); p < 0.01], Platelet Count (241.42 ± 75.35 vs 213.94 ± 56.74 mm3; p < 0.05) and fibrinogen (388.93 ± 107.27 vs 354.33 ± 89.35 mg/dl; p < 0.05). We used the logistic regression analysis to detect the independent predictors of aspirin resistance. Lipoprotein(a) was found to be the only independent risk factor to identify aspirin resistance (p < 0.05; OR: 1.302; CI 95 % : 1.003–1.688).
Although the potential mechanisms of aspirin resistance still remains uncertain, we found that platelet responsiveness to aspirin is reduced in patients with high levels of Apolipoprotein B and lipoprotein(a). Our work demonstrate that lipoprotein(a) is an independent risk factor for aspirin resistance possibly due to the interaction of Apolipoprotein(a) with human platelets.