Effect of different aspirin regimens on the VerifyNow Aspirin assay. Shown are individual data on platelet function measured by the VerifyNow Aspirin assay and expressed in arbitrary response units measured in the different phases of the study, including baseline, washout, and randomized aspirin regimens. During washout, patients took enteric-coated aspirin 100 mg once daily. Horizontal lines indicate medians. Each symbol indicates 1 patient across different treatments. *P < .001 versus baseline, washout, and plain aspirin; #P < .05 versus baseline, washout, plain aspirin, and 100 mg enteric-coated aspirin twice daily. WO indicates washout; od, once daily; bid, twice daily; and EC, enteric-coated.