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.