BACKGROUND AND PURPOSE: U.K ambulance services assess patients with suspected 
stroke using the Face Arm Speech Test (FAST). The Recognition Of Stroke In the 
Emergency Room (ROSIER) tool has been shown superior to the FAST in identifying 
strokes in emergency departments but has not previously been tested in the 
ambulance setting. We investigated whether ROSIER use by ambulance clinicians 
can improve stroke recognition.
METHODS: Ambulance clinicians used the ROSIER in place of the FAST to assess 
patients with suspected stroke. As the ROSIER includes all FAST elements, we 
calculated a FAST score from the ROSIER to enable comparisons between the two 
tools. Ambulance clinicians' provisional stroke diagnoses using the ROSIER and 
calculated FAST were compared with stroke consultants' diagnosis. We used 
stepwise logistic regression to compare the contribution of individual ROSIER 
and FAST items and patient demographics to the prediction of consultants' 
diagnoses.
RESULTS: Sixty-four percent of strokes and 78% of nonstrokes identified by 
ambulance clinicians using the ROSIER were subsequently confirmed by a stroke 
consultant. There was no difference in the proportion of strokes correctly 
detected by the ROSIER or FAST with both displaying excellent levels of 
sensitivity. The ROSIER detected marginally more nonstroke cases than the FAST, 
but both demonstrated poor specificity. Facial weakness, arm weakness, seizure 
activity, age, and sex predicted consultants' diagnosis of stroke.
CONCLUSIONS: The ROSIER was not better than the FAST for prehospital recognition 
of stroke. A revised version of the FAST incorporating assessment of seizure 
activity may improve stroke identification and decision making by ambulance 
clinicians.