The Prehospital Selection of Acute Stroke Patients

The effective treatment of acute ischemic stroke is limited to administration of intravenous tissue-type plasminogen activator within the first 4.5 hours from symptoms onset or endovascular thrombectomy up to 6(8) hours from the symptoms onset. Intravenous thrombolysis can be administered in the nearest Primary Stroke Centers (PSC).

In the case of large vessel occlusion, the endovascular therapy (mechanical thrombectomy) is utilized. Mechanical thrombectomy is offered only in Comprehensive Stroke Centers (CSC), due to the necessary presence of the special endovascular team during the procedure.

Practically, there are two options to transport patients for endovascular treatment. If the first one is used, then all suspected stroke patients are transported to primary stroke centers only. Then, rapid examinations are provided and, if the patient is determined to be having a stroke, the administration of intravenous thrombolysis occurs. Patients with diagnosis of stroke and large vessel occlusion are consequently transported to Comprehensive Stroke Center in order to receive mechanical thrombectomy. This first choice accelerates thrombolysis administration but delays endovascular procedures.

The second option entails selection of patients with suspected LVO stroke on site of stroke onset, and such patients are directly transported to Comprehensive Stroke Centers. The second choice accelerates endovascular procedures, but may delay intravenous thrombolysis. The disadvantage of this might be the overloading of the CSC with misdiagnosed patients (stroke mimics or non LVO stroke patients).

We can identify suspected stroke patients pre-hospitably with relative accuracy. The FAST test is a very simple and highly specific tool to identify stroke patients.* It consists of four items Face, Arm, Speech, and Time. Unfortunately, the FAST test is not able to evaluate the severity of the stroke, which is probably linked to the occlusion of large artery.

The only one test (RACE test) was prospectively studied to evaluate its sensitivity and specificity for diagnosis of large vessel occlusion.

In the hospital (stroke centre), we recognize the stroke severity according to NIHS scale, but both these scales are not suitable for emergency service for its difficulty.

Therefore, we desined a very simple new test - FAST PLUS test for the identification of the severe stroke patients on site, immediately at the onset of stroke. FAST PLUS test consists of two parts: the first one is the well-known FAST test which selects all suspected stroke patients and consists of the following evaluations: Speech (scored 0-1), Facial palsy (0-1), any failure of Arm motor function (0-1), time (0-1). The time means the speed of onset of symptoms during 30 minutes. The second part of the FAST PLUS test evaluates only the presence of severe arm or leg motor deficit (scored 0-1) and the unilateral occurrence of this motor function deficit (scored 0-1). (Figure one) The working hypothesis: We assume that the patients with clinically severe stroke and positive FAST PLUS test have a high probability of the presence of large cerebral vessel occlusion.

The aims of study:

1. The validation of the new pre-hospital test - FAST PLUS - to identify the stroke patients with LVO. The objective of our study is to evaluate the predictive value of the FAST PLUS test in the detection of patients with acute stroke and large vessel occlusion (LVO) when it is used by medical emergency technicians during the pre-hospital phase.

We presume that stroke severity, according to item 4 and 5 in NIHSS is linked to occlusion of ACM M1 or intracranial ICA. The FAST PLUS test consists of two parts (fig. 1), the first one is FAST test for identifying patients with stroke. The second part of test has three items, and evaluates the severity of hemiparesis and unilateral disabilities. The FAST PLUS test is positive when at least two items are positive in the first part (Time must be always positive + the presence of one of three symptoms at least) and all three items are positive in the second part.

1. The second aim of study is to determine the inter-rater variability between emergency technician and stroke specialist in evaluation NIHS scale, items 4 and 5 only. The agreement means the agreement in the severe hemiparesis evaluation between paramedics (FAST PLUS test positive) and stroke specialist examination(NIHSS 3 or 4 points in item 4,5 NIHSS) .
2. The third aim of study is to shorten the time between the onset of stroke to hospital entry or the time from the arriving of emergency service on site of stroke to hospital door after implementation of FAST PLUS test to the daily medical practice.

The first phase:

The creation of educational material for emergency technicians. The second phase: The education and testing of emergency technicians via e-learning and web seminars. The aim of the education is to learn whether the Emergency service is using the FAST PLUS test correctly.

We plan 6 months time period for the first and the second phase of study.

The third phase:

A/ to collect 400 FAST PLUS tests from the stroke patients up to 12 hours from the stroke onset to hospital arrival.

B/ to calculate the primary secondary and tertiary outcome measures of study

We plan 12 months time period for the third phase of study.

For statistical analysis, X software was used. Receiver operating curves and areas under receiver operating curve (c-statistics) were calculated as a measure of predictive ability for LVO of the FAST plus test. Ideal prediction produces a c-statistic of 1.00; precision no better than chance is associated with c-statistic of ≤0.50. Correlation between both scales (FAST test second part and NIHSS items 4 and 5) was analyzed with the nonparametric Spearman coefficient.

Cross tables for different cutoff values of the FAST plus test were used to evaluate sensitivity, specificity, positive predictive value, negative predictive values, and overall accuracy for the presence of VO.