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. 2020 Aug;37(8):474-479.
doi: 10.1136/emermed-2019-208902. Epub 2020 May 8.

Positive predictive value of stroke identification by ambulance clinicians in North East England: a service evaluation

Graham McClelland  1   2 , Darren Flynn  3 , Helen Rodgers  2 , Christopher Price  2
Affiliations

Positive predictive value of stroke identification by ambulance clinicians in North East England: a service evaluation

Graham McClelland et al. Emerg Med J. 2020 Aug.

Abstract

Introduction/background: Accurate prehospital identification of patients who had an acute stroke enables rapid conveyance to specialist units for time-dependent treatments such as thrombolysis and thrombectomy. Misidentification leads to patients who had a 'stroke mimic' (SM) being inappropriately triaged to specialist units. We evaluated the positive predictive value (PPV) of prehospital stroke identification by ambulance clinicians in the North East of England.

Methods: This service evaluation linked routinely collected records from a UK regional ambulance service identifying adults with any clinical impression of suspected stroke to diagnostic data from four National Health Service hospital trusts between 1 June 2013 and 31 May 2016. The reference standard for a confirmed stroke diagnosis was inclusion in Sentinel Stroke National Audit Programme data or a hospital diagnosis of stroke or transient ischaemic attack in Hospital Episode Statistics. PPV was calculated as a measure of diagnostic accuracy.

Results: Ambulance clinicians in North East England identified 5645 patients who had a suspected stroke (mean age 73.2 years, 48% male). At least one Face Arm Speech Test (FAST) symptom was documented for 93% of patients who had a suspected stroke but a positive FAST was only documented for 51%. Stroke, or transient ischaemic attack, was the final diagnosis for 3483 (62%) patients. SM (false positives) accounted for 38% of suspected strokes identified by ambulance clinicians and included a wide range of non-stroke diagnoses including infections, seizures and migraine.

Discussion: In this large multisite data set, identification of patients who had a stroke by ambulance clinicians had a PPV rate of 62% (95% CI 61 to 63). Most patients who had a suspected stroke had at least one FAST symptom, but failure to document a complete test was common. Training for stroke identification and SM rates need to be considered when planning service provision and capacity.

Keywords: diagnosis; prehospital care; stroke.

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Conflict of interest statement

Competing interests: GM reports grants from the Stroke Association, during the conduct of the study. DF reports grants from the National Institute for Health Research (Programme Grants for Applied Research, title: Promoting Effective and Rapid Stroke care (PEARS), project number: RP-PG-1211-20012), during the conduct of the study. HR reports grants from the NIHR, during the conduct of the study; personal fees from Bayer, outside the submitted work; and member of NIHR HTA CET panel 2010–2014. CP reports grants from the Stroke Association, during the conduct of the study.

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