VWF and ischemic stroke: Similarly, in a large prospective study, Sonneveld and colleagues found that individuals who had both the lowest ADAMTS13 activity (≤25th percentile) and the highest VWF:Ag levels (≥75th percentile) had an increased risk of ischemic stroke compared with the remaining individuals.[16] More prospective studies are needed to further establish the role of low ADAMTS13 levels as a risk factor for ischemic stroke.