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Evaluation of Resistance to Anti-platelet Therapy in Patients with Coronary Heart Disease in a Developing Country by Mostafa Q. Al Shamiri, Abelgalil M. Abdel Gader, Nervana M. Bayoumy

Background: Resistance to anti-platelet therapy whether defined by the laboratory detection of platelet function or the recurrence of cardiovascular events, has received extensive coverage in the literature coming predominantly from developed countries and very scanty information comes from developing countries. We aim to document the prevalence of aspirin and clopidogrel resistance in Saudi patients with coronary heart disease (CHD) and to probe the possible responsible mechanism[s].
Methods: 238 patients with CHD were enrolled from the outpatient clinic and wards of King Khalid University Hospital, Riyadh. Platelet function testing was undertaken using both optical aggregometry in platelet rich plasma as well as the Platelet Function Analyzer [PFA100] which uses whole blood.
Results: Agonist-induced platelet aggregation in response to arachidonic acid-induction: The prevalence of residual activity was detected in 12.6% patients. Resistance to clopidogrel as reflected by the residual aggregation responses to ADP was detected in 25.7%. PFA100 closure time: Closure times for collagen and epinephrine cartridges that are shorter than the maximum for local reference of 84 - 198 seconds were detected in around 30% of patients on therapy. There was no significant relationship between diabetes mellitus, smoking, dyslipidemia, or consumption of non-steroidal anti-inflammatory drugs and the resistance to anti-platelet therapy.
Conclusions: Resistance to anti-platelet therapy is quite prevalent among patients with CHD in Saudi Arabia and compares favorably with reports in the literature. However, the lack of a significant relationship between resistance to antiplatelet therapy and the above-mentioned conditions could be due to small numbers.

DOI: 10.7754/Clin.Lab.2013.131006