Objective: Numerous screening tools have emerged in an effort to identify patients with emergent large vessel occlusion (ELVO) for mechanical thrombectomy (MT). The vision, aphasia, and neglect (VAN) screening tool was designed as a quick evaluation of cortical function to predict ELVO and was shown to be effective when used in the emergency room in predicting ELVO with a 100% sensitivity and 90% specificity in the pilot study of 62 patients. The objective of this study was to evaluate the VAN tool as applied to a large patient population and assess its ability to predict ELVO.
Methods: Emergency visits that resulted in diagnosis of stroke or received thrombolysis for stroke in a community hospital over 18 months were reviewed. The VAN tool was applied, using components of initial NIHSS to identify changes in vision, language, or attention coupled with weakness. Patients were also screened for NIHSS ≥6. These two indices were evaluated for ability to predict ELVO and then candidacy for MT based on guideline criteria for MT.
Results: Of 617 patient cases reviewed, 159 (25.9%) were VAN positive while 233 (37.9%) had an NIHSS ≥6. Sixty-four (64) patients (10.4%) had ELVO. The VAN score had a sensitivity of 61% and a specificity of 76.8% for predicting ELVO, while an NIHSS value ≥6 had a sensitivity of 71.7% and a specificity of 63.6%. Of 38 VAN positive patients with ELVO, only 18 met all current guideline criteria for MT, representing only 11% of all VAN positive patients. Of 43 patients with an NIHSS ≥6 who had ELVO, 19 met criteria for MT, 8.2% of all NIHSS ≥6 patients. Only 19 of 617 stroke patient cases reviewed 19 had ELVO eligible for MT (3.1%).
Discussion: This study demonstrates that in a much larger population than that of the pilot study, the VAN screening tool for ELVO has a lower sensitivity and specificity than believed. Barring limitations, this population is ten times as large as the pilot study and shows that ELVO as well as ELVO meeting criteria for MT among VAN positive patients are less common than previously predicted by the VAN tool. Continued work needs to analyze and compare ELVO screening tools for predicting ELVO, and guidelines for MT need to adapt in a rapidly evolving field, especially with this and other studies suggesting an even larger population could benefit from MT.