CASE SERIES Predictors of false-positive stroke thrombectomy transfers

Background Most patients with large vessel occlusion (LVO) stroke need to be transferred to receive thrombectomy. To save time, the decision to transfer often relies on clinical scales as a surrogate for LVO rather than imaging. However, clinical scales have been associated with high levels of diagnostic error. The aim of this study is to define the susceptibility to overdiagnosis of our current transfer decision process by measuring the rate of non-treatment transfers, the most common reasons for no treatment and potential predictors. Methods Clinical and transfer data on consecutive patients transferred to a single endovascular capable centre for possible thrombectomy via stroke code activation were retrospectively reviewed. Whether patients underwent the procedure, why they did not undergo the procedure, and other clinical and logistical predictors were recorded. χ tests and multivariate logistic regression analysis were performed. Results From 2015 to 2016, 105/192 transferred patients (54%) did not undergo thrombectomy and the most common reason was absence of a LVO found on CTA after transfer (71/104 (68%)). 14/16 (88%) with a National Institutes of Health Stroke Scale (NIHSS) score <10 did not undergo thrombectomy while 41/78 (52%) with a NIHSS>20 underwent thrombectomy (p<0.001). Helicopter use was associated with no treatment (p=0.004) while arrival within 5 hours was associated with treatment (p<0.001). Conclusions Clinical scales appear to overdiagnose LVO and may be responsible for the majority of our stroke code transfers not undergoing thrombectomy. Primary stroke centres therefore have reason to develop the capability to rapidly acquire and interpret a CTA in patients with suspected LVO prior to transfer. Such efforts may reduce the costs associated with unnecessary thrombectomy transfers. INTRODUCTION For nearly 20 years, hospitals caring for patients with acute stroke have been organised to deliver intravenous thrombolysis. While robust level 1a evidence was published in 2015 proving clinical benefit for mechanical thrombectomy in acute anterior circulation large vessel occlusions (LVOs), only about 10% of the 1111 primary stroke centres in the US are able to reliably provide mechanical thrombectomy. As a result, most patients initially evaluated and deemed to have a LVO need to be transferred. Over the last 2 years, our stroke team has noticed a large number of thrombectomy transfers who do not end up undergoing the procedure. To minimise time to recanalisation, the decision to transfer a patient for thrombectomy is often based on the severity of the clinical exam rather than brain vascular imaging. As suggested by American Heart Association (AHA) guidelines, National Institutes of Health Stroke Scale score (NIHSS)>6 is often used as a surrogate marker for the presence of a LVO. Turc et al evaluated the ability of 13 clinical scores to predict large artery occlusions in over 1000 patients and found higher than expected false negative and false positive rates. Furthermore, patient transfers for potential thrombectomy have considerable costs, which include, but are not limited to, ambulance/helicopter services, call-pay for the neuroendovascular and stroke neurology team, repeat imaging, and a temporary suspension of what all members of the team are doing to await patient arrival. Sonig et al evaluated 1 311 511 National Inpatient Sample stroke admissions from 2008 to 2010 and found that each transferred patient undergoing tissue plasminogen activator (tPA) and thrombectomy had a mean expenditure of $27 000 more than those who were not transferred. Thus, despite the potential to incur significant unnecessary costs, the decision to transfer is currently based on an oblique measure of a LVO. In this study, we measure the frequency of nontreatment transfers since the publication of the positive thrombectomy trials and ascertain the most common reasons why transferred patients do not undergo thrombectomy. Our study objective is to find potential predictors of non-treatment transfers based on the limited clinical information available during the initial assessment at the transferring hospital. In doing so, we may be able to tailor strategies to improve the transfer decision process. METHODS Stroke transfer process The stroke service is staffed with five stroke neurologists who provide 24/7/365 coverage via a dedicated telephone hotline or telestroke. The initial determination for each consultation is eligibility for intravenous thrombolysis. If there is clinical suspicion for a disabling stroke due to a LVO, arrangements are made for transfer. Considerations for transfer include NIHSS>6; neurological examination findings suggestive of cortical involvement, such as gaze preference, neglect, or motor deficit with language impairment; onset of symptoms 1 of 4 Yi J, et al. J NeuroIntervent Surg 2017;9:834–836. doi:10.1136/neurintsurg-2017-013043 Ischemic stroke To cite: Yi J, Zielinski D, Ouyang B, et al. J NeuroIntervent Surg 2017;9:834–836. University of Illinois at Chicago, Chicago, Illinois, USA Department of Neurological Surgery, Rush University Medical Center, Chicago, Illinois, USA Department of Neurological Sciences, Rush University Medical Center, Chicago, Illinois, USA Correspondence to Dr Michael Chen, 1725 West Harrison Street, Suite 855, Chicago, IL 60612, USA; michael_ chen@ rush. edu Received 18 February 2017 Revised 7 March 2017 Accepted 8 March 2017 Published Online First 30 March 2017 group.bmj.com on September 7, 2017 Published by http://jnis.bmj.com/ Downloaded from