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Predictive value of the Ontario prehospital stroke screening tool for the identification of patients with acute stroke


Background — In 2005, a prehospital stroke screening tool was implemented in Toronto, Ontario, Canada. Patients identified by paramedics through the use of this tool in the field were transported to a regional stroke center under an acute stroke protocol.

Objective — To determine the positive predictive value (PPV) of the Ontario Prehospital Stroke Screening Tool for identification of acute stroke at a single stroke center. 

Methods — We conducted a retrospective analysis of consecutive patients transported to a regional stroke center under the prehospital acute stroke protocol over a 12-month period. Final diagnoses, treatments, andoutcomes were abstracted from a provincial registry. Rates of fibrinolysis were compared with those for the 12-month period prior to implementation of the stroke protocol.

Results — Three hundred twenty-five patients were triaged under the emergency medical services (EMS) acute stroke protocol over the study period. The PPV of the screening tool was 89.5% (95% confidence interval [CI]: 85.7–92.7%) for acute stroke. Thirty-four patients (11%) had nonstroke conditions, with the most common being seizure (4%). The rate of administration of tissue plasminogen activator (tPA) for all patients with suspected stroke increased from 5.9% to 10.1% (p = 0.04) compared with the rate in the 12-month period prior to implementation of the acute stroke protocol. The tPA rate for patients arriving under the stroke protocol was 17.2%. Most patients (75%) receiving tPA arrived from outside the hospital catchment area.

Conclusions — In this preliminary study, the Ontario Prehospital Stroke Screening Tool had a high PPV for acute stroke andappeared to be effective for identifying patients who required triage to a single regional stroke center. Following implementation of a citywide acute stroke protocol using this screening tool, we observed an increase in the number of patients who were eligible for and received fibrinolysis at our stroke center.



Chenkin J, Gladstone DJ, Verbeek PR, Lindsay P, Fang J, Black SE, Morrison L. Prehosp Emerg Care. 2009; 13(2):153-9.

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