Abstract 192: Trends in Carotid Imaging in the VA Health System Following Choosing Wisely: An Interrupted Time Series Analysis

Background: The majority of carotid imaging is performed on asymptomatic patients, those without stroke or transient ischemic attack, for whom the evidence for carotid revascularization is limited. In 2013, three Choosing Wisely campaigns identified carotid imaging for syncope (American Academy of Neurology), screening (American Academy of Family Physicians) and preoperatively before cardiac surgery (Society of Thoracic Surgeons) as low-value. The impact of these recommendations is unknown. Methods: We compared annual rates of carotid imaging in the VA Health System between 2007 and 2016. As administrative carotid imaging codes are non-specific, we used natural language processing to identify carotid imaging, including ultrasound, computed tomography angiography (CTA) and magnetic resonance angiography (MRA). We reviewed the study reason listed in radiology records to develop a lexicon of test indications for identifying imaging for syncope, preoperative testing and carotid bruits. We conducted an interrupted time series analysis to determine whether trends in overall and indication-specific asymptomatic carotid imaging changed, comparing imaging rates prior to the recommendations (2007-2012) and following their release (2014-2016). Results: We identified 773,044 carotid images for asymptomatic indications (mean age, 69.9 years; 96.5% men) including 720,961 ultrasounds, 28,979 CTAs, and 24,539 MRAs. From 2007 to 2016 the annual rate of asymptomatic imaging decreased from 10.79 to 10.35 images per 1,000 veterans (rate ratio 0.96; P<0.001). Annual rates of imaging for bruits also decreased while imaging for syncope and preoperative evaluation increased (rate ratios: 0.62, 1.08 and 1.59, all P<.0001) (Figure). Rates of asymptomatic imaging declined by 1.01% annually (95% CI -1.18% to -0.84%) prior to Choosing Wisely, with a change to a flat rate in the post-period (0.12%; 95% CI -0.37% to 0.62%). Trends in annual rates of imaging for syncope and preoperative evaluation increased following Choosing Wisely, while the rate of decrease of imaging for bruits diminished. Conclusions: The release of 3 Choosing Wisely guidelines targeting carotid imaging did not reduce overall or indication specific rates of asymptomatic carotid imaging in the VA Health System.