Background Most large vessel occlusion (LVO) stroke patients need to be transferred in order to receive thrombectomy. To save time, the decision to transfer often relies on clinical scales as a surrogate for LVO rather than imaging. Using this approach, our stroke service has noted a higher than expected rate of false-positive transfers. The aim of this study is to define our current transfer decision process’s susceptibility to overdiagnosis 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 our endovascular capable center for possible thrombectomy were retrospectively reviewed. Whether patients underwent procedure, why they did not undergo procedure, and other clinical and logistical predictors were recorded. Chi-square tests and multivariate logistic regression analysis were performed.

Results From 2015–2016, x 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 NIHSS <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 transfers not undergoing thrombectomy. Primary stroke centers have reason to develop the capability to rapidly acquire and interpret a CTA in suspected LVO patients prior to transfer. Such efforts may reduce costs associated with unnecessary thrombectomy transfers.

Disclosures J. Yi: None. D. Zielinski: None. B. Ouyang: None. M. Chen: 2; C; Genentech, Medtronic, Stryker, Penumbra.