Improving Prehospital Stroke Diagnosis Using Natural Language Processing of Paramedic Reports

Stroke. 2021 Aug;52(8):2676-2679. doi: 10.1161/STROKEAHA.120.033580. Epub 2021 Jun 24.


Background and purpose: Accurate prehospital diagnosis of stroke by emergency medical services (EMS) can increase treatments rates, mitigate disability, and reduce stroke deaths. We aimed to develop a model that utilizes natural language processing of EMS reports and machine learning to improve prehospital stroke identification.

Methods: We conducted a retrospective study of patients transported by the Chicago EMS to 17 regional primary and comprehensive stroke centers. Patients who were suspected of stroke by the EMS or had hospital-diagnosed stroke were included in our cohort. Text within EMS reports were converted to unigram features, which were given as input to a support-vector machine classifier that was trained on 70% of the cohort and tested on the remaining 30%. Outcomes included final diagnosis of stroke versus nonstroke, large vessel occlusion, severe stroke (National Institutes of Health Stroke Scale score >5), and comprehensive stroke center-eligible stroke (large vessel occlusion or hemorrhagic stroke).

Results: Of 965 patients, 580 (60%) had confirmed acute stroke. In a test set of 289 patients, the text-based model predicted stroke nominally better than models based on the Cincinnati Prehospital Stroke Scale (c-statistic: 0.73 versus 0.67, P=0.165) and was superior to the 3-Item Stroke Scale (c-statistic: 0.73 versus 0.53, P<0.001) scores. Improvements in discrimination were also observed for the other outcomes.

Conclusions: We derived a model that utilizes clinical text from paramedic reports to identify stroke. Our results require validation but have the potential of improving prehospital routing protocols.

Keywords: diagnosis; machine learning; natural language processing; patient; retrospective studies.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aged
  • Aged, 80 and over
  • Allied Health Personnel / standards*
  • Chicago / epidemiology
  • Emergency Medical Services / methods
  • Emergency Medical Services / standards*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Natural Language Processing*
  • Research Report / standards*
  • Retrospective Studies
  • Stroke / diagnosis*
  • Stroke / epidemiology