The FAST score is a straightforward public health tool developed to enable the swift recognition of stroke symptoms in any setting. It functions as a mnemonic that simplifies a complex neurological event into easily identifiable physical signs for both laypersons and first responders. This rapid, pre-hospital assessment is designed to expedite the activation of emergency medical services (EMS) and streamline patient care in the acute setting. The assessment quickly screens individuals suspected of having a stroke, initiating an urgent medical response and reducing delays for time-sensitive treatments.
The Four Components of the FAST Assessment
The four letters that make up the FAST mnemonic represent the primary physical signs and the single most time-sensitive piece of information necessary for immediate stroke care.
The first component, “F” for Face, is assessed by observing the individual for facial weakness or drooping. A common way to check this is to ask the person to smile, which often reveals an uneven smile where one side of the mouth does not move or droops downward. This asymmetry results from damage to the brain area controlling the facial nerves.
The second letter, “A” for Arm, checks for motor weakness in the limbs, a condition medically known as hemiparesis. To assess this, the person is asked to raise both arms in front of them with palms up and hold them there for about ten seconds. A positive sign is indicated if one arm drifts downward or cannot be raised at all, suggesting a lack of muscle control on one side of the body.
Next, “S” represents Speech difficulty, which covers a range of communication problems. This can manifest as slurred speech (dysarthria), the inability to find words, or speaking in incomprehensible phrases (aphasia). The assessment typically involves asking the person to repeat a simple, common phrase to gauge their ability to articulate and comprehend language. The presence of garbled or slow speech is considered a positive finding.
The final letter, “T” for Time, is not a physical symptom but the most important data point in the entire assessment process. This refers to the time the symptoms were first noticed, or the “last known well” time. This specific moment is the baseline for determining a patient’s eligibility for clot-busting medications, making it a determinant of the subsequent treatment pathway. One or more of these three physical symptoms are present in approximately 88% of all stroke and transient ischemic attack (TIA) cases, confirming the high sensitivity of this simple screening tool.
Clinical Application and Time Sensitivity
The FAST assessment is widely used by emergency dispatchers, EMS personnel, and hospital triage nurses to rapidly screen for a potential stroke. The tool is effective because it can be administered quickly, often in under a minute, initiating the stroke alert system while the patient is still being transported. Prehospital stroke assessment by EMS shortens delays and ensures patients receive initial brain imaging sooner upon arrival at the emergency department (ED).
The urgency of this application is driven by the fact that stroke is a time-dependent event, where every minute that passes results in the loss of millions of brain cells. The speed of the assessment directly impacts the patient’s eligibility for acute interventions, such as intravenous thrombolysis (administering a clot-dissolving drug like alteplase). The therapeutic window for this medication is narrow, with the greatest benefit observed when treatment begins within three hours of symptom onset. A positive FAST assessment allows EMS to notify the receiving hospital in advance, activating the in-house stroke team to prepare for immediate intervention.
Interpreting the FAST Score and Subsequent Actions
The FAST assessment operates on a binary principle: the presence of even one of the three physical symptoms (Face, Arm, or Speech) constitutes a positive score, which immediately triggers the full stroke protocol. A positive FAST assessment signals emergency responders to bypass closer, non-specialized facilities and transport the patient directly to a Comprehensive Stroke Center or a Primary Stroke Center. These specialized hospitals are equipped with the personnel and technology required to manage acute stroke, including 24/7 access to neurological expertise and advanced imaging.
Upon arrival at the ED, the immediate focus is on stabilization and a comprehensive neurological assessment, often using a more detailed scale like the NIH Stroke Scale. The patient is rushed for emergent brain imaging, typically a non-contrast Computed Tomography (CT) scan, which must be completed quickly, ideally within 25 minutes of arrival. The primary goal of this initial scan is to rule out a hemorrhagic stroke (bleeding in the brain), which would make the patient ineligible for thrombolytic therapy.
If the CT scan shows no evidence of hemorrhage, the patient is presumed to have an ischemic stroke (a clot blocking blood flow). The stroke team must then determine eligibility for clot-busting medication within a strict timeframe. This entire process, from ED arrival to administering the intravenous thrombolytic, must occur rapidly, with a goal of less than 60 minutes.