FAST Exam for Stroke Recognition
The FAST exam is a simple, validated stroke recognition tool that assesses three key physical findings—Face drooping, Arm weakness, and Speech difficulty—with Time emphasizing the urgency to activate emergency medical services immediately when any of these signs are present. 1
Components of the FAST Assessment
The FAST acronym stands for four critical elements used to identify acute stroke 1:
Face: Assess for facial drooping or asymmetry, typically on one side of the face. Ask the person to smile and observe whether one side of the face droops or appears uneven. 1
Arms: Evaluate for arm weakness or drift. Ask the person to raise both arms and hold them extended. Observe whether one arm drifts downward or cannot be raised at all. 1
Speech: Check for speech difficulty, including slurred speech, inability to speak, or difficulty understanding speech. Ask the person to repeat a simple sentence and assess clarity and comprehension. 1
Time: Emphasizes that time is critical—if any of these signs are present, emergency medical services (EMS) must be activated immediately (call 911). Time also refers to documenting when symptoms began or when the person was last known to be normal. 1
Clinical Application and Validation
The 2024 American Heart Association/American Red Cross Guidelines strongly recommend using FAST or the essentially identical Cincinnati Prehospital Stroke Scale to aid in acute stroke recognition in adults. 1
Key Performance Characteristics:
FAST is specifically designed for laypeople and first aid providers, making it the most appropriate tool for non-medical personnel in the community setting. 1
The tool demonstrates pooled sensitivity of approximately 80% for stroke detection, though specificity is more limited at around 42%, meaning it casts a "wide net" to avoid missing strokes at the cost of some false positives. 1
When used by EMS personnel on-scene, FAST shows higher positive predictive value (73%) compared to use by emergency call center dispatchers (56%), suggesting it performs better with direct patient assessment. 2
Implementation in Emergency Care Systems
Prehospital Setting:
Canadian Stroke Best Practice Recommendations (2018) specify that EMS personnel should screen all suspected stroke patients using a validated tool that includes FAST components. 1
EMS dispatchers should use FAST criteria during the initial emergency call to recognize probable stroke and trigger priority response and transport. 1
On-scene time should be minimized to ideally 20 minutes or less when FAST signs are positive and the patient presents within the treatment window. 1
Critical Timing Considerations:
Immediate EMS activation is associated with earlier ED arrival, quicker evaluation, more rapid treatment, and better eligibility for time-sensitive interventions like thrombolysis and thrombectomy. 1
Patients identified as stroke by dispatchers using FAST criteria experience significantly reduced transportation times compared to stroke patients not identified during the initial call. 1
Important Limitations and Pitfalls
Recognition Gaps:
FAST primarily detects anterior circulation strokes and may miss posterior circulation strokes presenting with symptoms like diplopia, visual field deficits, vertigo, or ataxia. 3
A negative FAST does not rule out stroke—studies show that 58 patients identified by emergency call centers and 27 by ambulances had confirmed stroke/TIA despite negative FAST assessments. 2
Public awareness of FAST remains low, with only 12% of stroke patients and bystanders in one study aware of the campaign, and poor recall of all components even among those aware. 4
Language and Symptom Description Issues:
The terminology used in FAST may not match patients' actual symptom experience—less than half of those experiencing "weakness or paralysis" felt this exactly described their symptoms. Common patient descriptors include "face or mouth droop," "trouble using or coordinating arm," "numbness," and "slurring or loss of speech." 4
FAST can be positive in non-stroke conditions, with 44% of patients with positive FAST from emergency call centers ultimately receiving non-stroke diagnoses at discharge. 2
Additional Assessment Considerations
When FAST signs are present, first aid providers should also measure capillary blood glucose if available and this does not delay EMS activation, as hypoglycemia can mimic stroke symptoms. 1
For patients demonstrating any FAST signs, EMS personnel should perform a second screening using tools validated to assess stroke severity to identify potential candidates for advanced interventions like endovascular thrombectomy. 1
Documentation of symptom onset time or time last known well is critical and should be obtained from the patient, family, or witnesses, as this determines eligibility for time-sensitive treatments. 1