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Enrollment Yield and Reasons for Screen Failure in a Large Prehospital Stroke Trial

Background and Purpose— The enrollment yield and reasons for screen failure in prehospital stroke trials have not been well delineated. Methods— The Field Administration of Stroke Therapy–Magnesium (FAST-MAG) trial identified patients for enrollment using a 2 stage screening process—paramedics in person followed by physician-investigators by cell phone. Outcomes of consecutive screening calls from paramedics to enrolling physician-investigators were prospectively recorded. Results— From 2005 to 2012, 4458 phone calls were made by paramedics to physician-investigators, an average of 1 call per vehicle every 135.7 days. A total of 1700 (38.1%) calls resulted in enrollments. The rate of enrollment of stroke mimics was 3.9%. Among the 2758 patients not enrolled, 3140 reasons for screen failure were documented. The most common reasons for nonenrollment were >2 hours from last known well (17.2%), having a prestroke condition causing disability (16.1%), and absence of a consent provider (9.5%). Novel barriers for phone informed consent specific to the prehospital setting were infrequent, but included: cell phone connection difficulties (3.2%), patient being hard of hearing (1.4%), insufficient time to complete consent (1.3%), or severely dysarthric (1.3%). Conclusions— In this large, multicenter prehospital trial, nearly 40% of every calls from the field to physician-investigators resulted in trial enrollments. The most common reasons for nonenrollment were out of window last known well time, prestroke confounding medical condition, and absence of a consent provider. Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT00059332.