Accuracy of emergency medical services-reported last known normal times in patients suspected with acute stroke

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 P P =0.019) were independent predictors of prolonged |ΔLKN|. Conclusions— EMS-reported LKN times were largely congruent with neurologist-determined times. Focused EMS training regarding wake-up stroke symptoms may further improve accuracy.