Variability of non-response to aspirin in patients with peripheral arterial occlusive disease during long-term follow-up

Non-responsiveness to aspirin as detected by laboratory tests may identify patients at high risk for future vascular events. The aim of this prospective study was to evaluate whether non-responsiveness to aspirin is stable over time. Ninety-eight patients with stable peripheral arterial occlusive disease (PAOD) treated with 100 mg/d aspirin were followed over a median timeframe of 17 months. Platelet function tests were performed initially and at follow-up using arachidonic acid-induced light transmittance aggregometry (LTA) in native platelet-rich plasma with the Behring Coagulation Timer® and by measuring the collagen-epinephrine closure time (CT) on a Platelet Function Analyzer (PFA-100®). When determining platelet function using LTA, four patients (4.1%) had residual platelet function (i.e., MaxAggr >=78%) despite aspirin treatment, whereas, according to the PFA-100® results, 12 patients (12.2%) were identified as non-responders (i.e., CT