Accuracy of Emergency Medical Services–Reported Last Known Normal Times in Patients Suspected With Acute Stroke David Curfman, MD; Lisa Tabor Connor, PhD; Hawnwan Philip Moy, MD; Laura Heitsch, MD; Peter Panagos, MD; Jin-Moo Lee, MD, PhD; David K. Tan, MD*; Andria L. Ford, MD, MSCI* Background and Purpose—The last known normal (LKN) time is a critical determinant of IV tissue-type plasminogen activator (IV tPA) eligibility; however, the accuracy of emergency medical services (EMS)-reported LKN times is unknown. We determined the congruence between neurologist-determined and EMS-reported LKN times and identified predictors of incongruent LKN times. Methods—We prospectively collected EMS-reported LKN times for patients brought into the emergency department with suspected acute stroke and calculated the absolute difference between the neurologist-determined and EMS-reported LKN times (|ΔLKN|). We determined the rate of inappropriate IV tPA use if EMS-reported times had been used in place of neurologist-determined times. Univariate and multivariable linear regression assessed for any predictors of prolonged |ΔLKN|. Results—Of 251 patients, mean and median |ΔLKN| were 28 and 0 minutes, respectively. |ΔLKN| was