Abstract WP260: Imaging Appropriateness Criteria May Guide Effective Use of CT Angiography in Acute Stroke Workup

Introduction: CT angiography (CTA) is a front-line imaging tool for the evaluation of acute stroke patients in the emergency department. In our experience, however, many CTAs performed for suspected stroke may not be appropriate and patients are found to have alternative diagnoses upon further work-up. We hypothesize that use of an evidence-based imaging guideline such as the American College of Radiology Appropriateness Criteria (ACR-AC) could facilitate more judicious use of CTA by identifying patients who are likely to have alternative diagnoses. Methods: We retrospectively reviewed patients who underwent CTA for stroke workup in the emergency department between January 2014 and January 2015. Patients evaluated for trauma, intracranial hemorrhage and known infarcts were excluded. Through PACS and EMR review, we identified 144 patients. Using a double-reader consensus method, we categorized each patient’s presenting symptoms based on the ACR-AC Neurologic Variants. Categories included: “usually appropriate,” “may be appropriate,” and “usually not appropriate”. We performed contingency table analyses using Fisher’s exact test and calculated odds ratios to correlate ACR-AC categories with CTA findings which explained stroke presentation such as arterial thrombosis, dissection, or high grade stenosis in a relevant vascular distribution. Results: Of the 144 patients who underwent CTA for stroke evaluation, 87 patients fell into the “usually appropriate” ACR-AC category, with 49 “may be appropriate” and 8 “usually not appropriate”. Within the first group, 19/87 CTAs were positive (21.8%) with an odds ratio of 4.98 (p=<0.01). In the second group, 3/49 CTAs were positive (6.1%) with an odds ratio of 0.26 (p=<0.03). In the third group, 0/8 CTAs were positive, with an odds ratio of 0.49 (p=0.61). Conclusion: Our data suggest that ACR-AC correlate with CTA findings relevant to stroke. Specifically, patients in the “usually appropriate” category were more likely to have a positive finding on CTA, while no positive CTAs were seen in the “usually not appropriate” category. These preliminary data suggest that the use of ACR-AC or similar criteria may aid clinical decision making and facilitate evidence-based use of CTA for suspected stroke workup.