• FAST Test Use in the Prehospital Setting: Better in the Ambulance than in the Emergency Medical Communication Center

    by Alan Batt. Last modified: 08/03/14

    FAST

    Summary

    • Prospective, descriptive study carried out in Stockholm, Sweden
    • During a 6 month period in 2008 all persons 18–85 years of age suspected of having a stroke with onset within 6 hours and with independence in activities of daily living were enrolled.
    • 900 patients enrolled
      • Control centre enrolled 677
        • Positive FAST was registered for 494 (74%)
        • Of these, 279 had a stroke/TIA diagnosis at discharge – this gives a PPV of 56%
        • Overall, 337 of the 677 (51%) were diagnosed with stroke/TIA at discharge
      • Ambulance crews enrolled 233
        • Positive FAST was registered for 148 (64%)
        • Of these, 108 had a stroke/TIA diagnosis at discharge – this gives a PPV of 73%
        • Overall, 135 of the 233 (58%) were diagnosed with stroke/TIA at discharge
      • At discharge 52% overall (n=472) had a diagnosis of stroke or TIA
    • This study shows that the FAST test fails to identify stroke in emergency calls to the control centre.
    • Even though FAST symptoms are frequently present in stroke patients the symptoms might not be obvious to those calling for help.
    • The FAST test has a higher PPV when used on the scene by the ambulance than by dispatchers in the control centre.
    • The FAST test may be a useful tool for prehospital identification of stroke/TIA but has limitations as the test can have false negatives and false positives.

    Some limitations of this study include

    • Education and experience level of ambulance personnel and control room operators (in particular with regards to FAST assessment) is not presented.
    • Study composition does not allow for sensitivity or specificity calculations as it is unknown how many patients fulfilling the study criteria were missed from inclusion in the study.
    • Whether FAST was expressed spontaneously, asked for or found at examination was not captured in this study.
    • During the time period of the study, only 31% of all strokes/TIA in the region of Stockholm were enrolled.

    Positive predictive value

    The positive predictive value (PPV) is defined as the probability that subjects with a positive screening test truly have the disease.

     \text{PPV} = \frac{\text{number of true positives}}{\text{number of true positives}+\text{number of false positives}} = \frac{\text{number of true positives}}{\text{number of positive calls}}
    • true positive is the event that the test makes a positive prediction, and the subject has a positive result – 
    • false positive is the event that the test makes a positive prediction, and the subject has a negative result – 
     
    Berglund A1, Svensson L, Wahlgren N, von Euler M. Face Arm Speech Time Test Use in the Prehospital Setting, Better in the Ambulance than in the Emergency Medical Communication Center. Cerebrovasc Dis. 2014 Feb 26;37(3):212-216. PMID: 24576912.

    Abstract

    Background

    Prehospital identification of acute stroke increases the possibility of early treatment and good outcome. To increase identification of stroke, the Face Arm Speech Time (FAST) test was introduced in the Emergency Medical Communication Center (EMCC). This substudy aims to evaluate the implementation of the FAST test in the EMCC and the ambulance service.

    Methods

    The study was conducted in the region of Stockholm, Sweden during 6 months. The study population consisted of all calls to the EMCC concerning patients presenting at least one FAST symptom or a history/finding making the EMCC or ambulance personnel to suspect stroke within 6 h. Positive FAST was compared to diagnosis at discharge. Positive predictive values (PPV) for a stroke diagnosis at discharge were calculated.

    Results

    In all, 900 patients with a median age of 71 years were enrolled, 667 (74%) by the EMCC and 233 (26%) by the ambulances. At discharge, 472 patients (52%) were diagnosed with stroke/transient ischemic attack (TIA), 337 identified by the EMCC (71%) and 135 (29%) by the ambulances. The PPV for a discharge diagnosis of stroke/TIA was 51% (CI 47-54%) in EMCC-enrolled and 58% (CI 52-64%) in ambulance-enrolled patients. With a positive FAST the PPV of a correct stroke/TIA diagnosis increased to 56% (CI 52-61%) and 73% (CI 66-80%) in EMCC- and ambulance-enrolled patients, respectively. Positive FAST from EMCC was also found in 44% of patients with a nonstroke diagnosis at discharge. A stroke/TIA diagnosis at discharge but negative FAST was found in 58 and 27 patients enrolled by the EMCC and ambulances, respectively.

    Conclusions

    The PPV of FAST is higher when used on the scene by ambulance than by EMCC. FAST may be a useful prehospital tool to identify stroke/TIA but has limitations as the test can be negative in true strokes, can be positive in nonstrokes, and FAST symptoms may be present but not identified in the emergency call. For the prehospital care situation better identification tools are needed.

    References

     
    1.

    Berglund A1, Svensson L, Wahlgren N, von Euler M. Face Arm Speech Time Test Use in the Prehospital Setting, Better in the Ambulance than in the Emergency Medical Communication Center. Cerebrovasc Dis. 2014 Feb 26;37(3):212-216. PMID: 24576912.

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    Alan Batt

    Alan Batt

    Paramedic, educator, researcher
    Alan is a critical care paramedic, paramedic educator and prehospital researcher, currently working around the world as an educator and researcher. He has previously worked and studied across Europe, North America and the Middle East. He holds a Graduate Certificate in Intensive Care Paramedic Studies, and an MSc in Critical Care. His main interests are in care of the elderly, end-of-life care, patient safety, professionalism (including role and identity), and paramedic education.

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