High on treatment platelet reactivity to aspirin and clopidogrel in ischemic stroke: A systematic review and meta-analysis

Emerging studies highlight high on-treatment of platelet reactivity (HTPR) as a major hindrance to the secondary prevention of cardiovascular ischemic events. The aim of this systematic review and meta-analysis is to assess the prevalence of HTPR in patients with ischemic stroke (IS) or transient ischemic attack (TIA) and reveal a possible relation with a higher risk of cerebrovascular event recurrence. Studies were selected if they reported absolute numbers or percentages of HTPR with ASA or clopidogrel in IS/TIA patients at any time point after the cerebrovascular event onset and assessed with any type of platelet function tests. We included 52 full-text studies with a total of 8364 patients. Overall, the pooled prevalence of HTPR was 24% (95%CI: 20-27%). In subgroup analyses, the prevalence of HTPR on ASA was 23% (95%CI: 20-28%), on clopidogrel 27% (95%CI: 22-32%) and on dual antiplatelet treatment (DAPT) 7% (95%CI: 5-10%). The overall analysis of all studies providing data on the risk of IS/TIA recurrence, indicates that the patients with HTPR had a significantly higher risk for IS/TIA recurrence (RR=1.81, 95%CI: 1.30-2.52; p<0.001). In conclusion the present study shows a significant lower prevalence of HTPR in DAPT and an increased rate of recurrent cerebrovascular ischemic events in patients presenting HTPR.