How do I perform the stroke FLOW (Face, Limb, Other, Speech, Time) examination?

How to Perform the Stroke FLOW Examination

I cannot provide guidance on performing a "stroke FLOW" examination because this acronym does not appear in any current stroke guidelines or validated stroke assessment tools. The evidence consistently supports using FAST (Face, Arms, Speech, Time) or the Cincinnati Prehospital Stroke Scale (CPSS) as the validated stroke recognition tools for prehospital and first aid settings 1.

The Correct Validated Stroke Assessment: FAST/CPSS

You should use the FAST assessment (Face, Arms, Speech, Time), which is identical to the Cincinnati Prehospital Stroke Scale, as these are the only tools validated for use by laypeople and first responders 1.

How to Perform FAST Assessment

F - Face (Facial Droop)

• Have the patient show their teeth or smile 1
• Normal: Both sides of face move equally 1
• Abnormal: One side of face does not move as well as the other side 1

A - Arms (Arm Drift)

• Have patient close their eyes and hold both arms straight out for 10 seconds 1
• Normal: Both arms move the same or both arms do not move at all 1
• Abnormal: One arm does not move or one arm drifts down compared with the other 1

S - Speech (Abnormal Speech)

• Have the patient say "you can't teach an old dog new tricks" 1
• Normal: Patient uses correct words with no slurring 1
• Abnormal: Patient slurs words, uses the wrong words, or is unable to speak 1

T - Time

• If any 1 of these 3 signs is abnormal, the probability of stroke is 72% 1
• Immediately activate EMS (call 911) 1

Performance Characteristics

The CPSS/FAST has demonstrated:

• Sensitivity: 59-97% when used by trained paramedics 1, 2
• Specificity: 89% when scored by prehospital providers 1
• After training in stroke assessment tools, paramedic sensitivity increased to 86-97% 1

Important Caveats

What FAST Misses

FAST fails to identify approximately 14% of acute ischemic strokes 3. The missed strokes typically present with:

• Gait imbalance or isolated leg weakness (42% of FAST-negative strokes) 3
• Visual symptoms including monocular vision loss, hemianopia, or diplopia (40% of FAST-negative strokes) 3
• Posterior circulation symptoms such as ataxia, vertigo, or dysarthria 1

BE-FAST: An Enhanced Alternative

BE-FAST (Balance, Eyes, Face, Arms, Speech, Time) improves stroke detection by adding balance and eye assessments 4, 3. This expanded tool:

• Reduces missed strokes from 14.1% to 4.4% 3
• Shows sensitivity of 91-97.8% compared to FAST's 58.7-76% for posterior circulation strokes 4
• Has lower specificity (53% vs 68%) resulting in more false positives 4

B - Balance: Check for sudden loss of balance, dizziness, or difficulty walking 3

E - Eyes: Check for sudden vision loss in one or both eyes, double vision, or visual field defects 3

Clinical Application Algorithm

1. Assess using FAST - takes less than 1 minute 1
2. If ANY component is positive: Activate EMS immediately 1
3. Document time of symptom onset or time last known well 1
4. Do not delay transport - on-scene time should be minimized 1
5. Provide pre-hospital notification to receiving facility 1

Common Pitfalls to Avoid

• Do not wait for multiple FAST components to be positive - a single abnormality warrants immediate EMS activation 1
• Do not perform extensive on-scene assessment - the goal is "recognize and mobilize" 1
• Do not dismiss isolated sensory symptoms, visual changes, or balance problems - these may represent posterior circulation strokes missed by FAST 1, 3
• Do not rely on FAST alone in emergency dispatch centers - it has lower positive predictive value (51%) when used by phone compared to on-scene assessment (58-73%) 5