Factors influencing multiplate whole blood impedance platelet aggregometry measurements, during aspirin treatment in acute ischemic stroke: a pilot study.

Among patients with stroke, the phenomenon of resistance to treatment with low-dose aspirin acetylsalicylic acid (ASA) is quite common. The study included 133 patients hospitalized with acute ischemic stroke. Impedance platelet aggregometry (IPA) and levels of vWF and thromboxane (TXB2) were assessed - with the efficacy of aspirin in daily clinical investigation. Responses to treatment with doses of 150 and 300 mg/day were measured. In addition, we analyzed the response of proinflammatory factors [fibrinogen, C-reactive protein (CRP), white blood corpuscles (WBC)], lipids and hemoglobin A1c, which may alter platelet aggregation response to treatment. After a week of treatment at 150 mg/day, ASA patients were classified as laboratory resistant (42%) or sensitive (58%). Values of IPA in the resistant group were significantly higher (472 ± 150 vs. 222 ± 59 AUC, P < 0.0001). In resistant patients were also found higher levels of fibrinogen (3.90 ± 0.89 vs. 3.46 ± 0.74 g/l, P = 0.0046), CRP (6.97 ± 5.66 vs. 4.17 ± 4.03 mg/l, P = 0.0011), WBC (9.2 ± 2.4 vs. 8.3 ± 2.2 × 10/l, P = 0.0207) and lower HDL cholesterol (46 ± 12 vs. 52 ± 15 mg/dl, P = 0.016). This research shows that aspirin resistance assessment by IPA well reflects the clinical status of patients and should be used routinely. Resistance generally fails to 'break' at higher doses, hence our suggestion that patients resistant to low doses of the drug immediately switch to a thienopyridine class antiplatelet agent, for example, clopidogrel.