Error in Calculation of Cutoff Values: In the Original Contribution entitled “Comparison of Platelet Function Tests in Predicting Clinical Outcome in Patients Undergoing Coronary Stent Implantation,” published in the February 24, 2010, issue of JAMA (2010;303:754-762), an error in the calculation of cutoff values occurred. Due to the negative concordance of 3 of the 8 tests evaluated in the Popular study, the initially calculated ROC curves were mirrored, leading to incorrect cutoff values being reported for these 3 tests. This specific error affects multiple numbers, percentages, and associated odds ratios with confidence intervals in several paragraphs, tables, and figures. The correctly calculated cutoff values do not have any effect on the predictability of the IMPACT-R test and the PFA-100 Collagen/ADP; however, with the corrected cutoff values, the Innovance PFA P2Y predicted the primary end point. In addition, in Figure 2 the lower line for Innovance P2Y indicates patients with an end point and should not have been dashed. The corrected article and supplemental materials were replaced on May 11, 2011. An accompanying letter appears in this issue of JAMA, and the article has been corrected online. We sincerely regret the errors in the initially calculated describes the discovery of this error and correction of this misclassification fully.