Response to Letter Regarding Article, “A Prospective Cohort Study of Patients With Transient Ischemic Attack to Identify High-Risk Clinical Characteristics”

We thank Drs Purroy and Kelly for their comments on our prospective derivation of a new risk score for emergency patients with suspected transient ischemic attack (TIA).1 To the best of our knowledge, the Canadian TIA Score is the first prediction score to be entirely derived prospectively in the emergency department. As such, we think that this score will outperform all versions of the ABCD2, which were derived using largely retrospective data and delayed specialist assessment. Although ABCD2 performed relatively well in administrative database studies, we found it performed only slightly better than chance alone in new emergency patients (C-statistic=0.56; 95% confidence intervals [0.47–0.65]).2 Clinical prediction tools need to be derived in …