the system, emergency call workers asked ambulance callers for the patient's age, chief complaint, speaking ability and previous history of illness. We analysed the relation between this information and the disease classification (ICD-10) coded by physicians in the emergency department at each patient's destination. A logistic model was used to estimate the probability of stroke occurrence at the time of emergency calls. Results There were 66 744 patients who were transported by ambulance

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... the study period. Among the 66 744 cases, this study targeted 60 791 patients whose triage data were complete. Out of these 60 791 cases, 2496 were coded as suffering a stroke (ICD-10: I60eI69) by emergency department physicians. The probability of stroke occurrence from the information given at the time of the emergency call was estimated quantitatively. Conclusion Stroke occurrence can be expressed as a probability (%) at the time of the emergency call. The probability can be used to establish a quick and smooth transport of patients to appropriate medical facilities.