Patients with acute ischemic stroke (AIS) may not need to undergo both computed tomography (CT) and MRI scans, according to a new study published in JAMA Network Open (2022; doi:10.1001/jamanetworkopen.2022.19416). While patients with acute ischemic stroke often undergo MRI in addition to CT, its association with clinical outcomes is "uncertain," the authors wrote.
"There are possible reasons why MRI may have added value to initial CT for patients with AIS," according to the researchers. "The MRI-derived information about stroke subtype, timing, or location may lead to better selection of treatments. Clear demonstration of infarction has been proposed as a means to enhance patient education and improve adherence to prescribed prevention regimens."
Noting the increased use of CT and MRI in the past 2 decades, and describing unnecessary medical imaging as "a major cause of preventable waste in the U.S. health care system," the researchers sought to assess whether clinical outcomes of patients with acute ischemic stroke with initial CT alone were non-inferior to those with additional MRI.
To that end, the authors conducted a retrospective observational propensity score-matched cohort study of clinical outcomes at discharge and 1 year for patients hospitalized with acute ischemic stroke. The study was conducted at an academic medical center between January 2015 and December 2017. Data collection from an electronic medical record system performed from May 2020 through January 2022 was not completely blinded. MRIs were conducted after initial diagnosis.
Noninferiority margins were based on the designs of previous randomized clinical trials of ischemic stroke treatments. Statistical analysis was performed in January 2022. Participants were adults hospitalized with acute ischemic stroke with admission diagnosis based on CT. Exclusion criteria were primarily missing data. From 508 eligible patients, all 123 cases with additional MRI were propensity-score matched to 123 controls without.
Among 246 participants-patients hospitalized with acute ischemic stroke-the median age was 68 years and 131 of participants were men. In this study of 246 patients, a diagnostic imaging strategy of initial CT alone was noninferior to initial CT plus additional MRI with regard to clinical outcomes at discharge and at 1 year.
Death or dependence at discharge occurred more often in patients with additional MRI (59 of 123; 48%) than in those with CT alone (52 of 123, or 42%). Stroke or death within 1 year after discharge determined for 225 of 235 (96%) survivors occurred more often in patients with additional MRI than in those with CT alone (14 of 112; 13%), meeting the 0.725 relative risk criterion for noninferiority.
"Results of this study suggest that further research is needed to determine which patients hospitalized with acute ischemic stroke benefit from MRI in addition to initial CT," the authors wrote.
The researchers observed over a number of years that MRIs were routinely ordered for many patients with ischemic stroke "for no clear reason or with no clear question to answer," stated William J. Powers, MD, Professor of Neurology at Duke University School of Medicine, and a co-author of the study. "Many books and reviews implicitly endorse this practice, but provide no evidence to support any beneficial effect on patient outcome. Our hypothesis was that, in this specific population in whom the diagnosis of ischemic stroke had already been made based on clinical presentation and CT, additional MRI would not lead to treatment changes that would improve outcome. We were hoping to show this and reduce the unnecessary use and expense of MRI."
With the exception of WAKE-UP, none of the randomized clinical trials that guide current therapy for ischemic stroke required MRI to determine eligibility, added Powers, noting that CT alone sufficed. "Thus, CT is sufficient to identify patients who would have met the RCT eligibility criteria and who can reasonably be expected to derive the same benefits of treatment."
Looking ahead, these findings could prove significant for the treatment and management of acute ischemic stroke patients. "Ideally, we should have more studies to determine the optimal imaging strategy for patients with a presentation consistent with ischemic stroke based on their clinical characteristics," Powers noted.
Until such data exist, he believes care teams should consider a key question when ordering imaging and other diagnostic tests. "Can the results of the test identify specific patient characteristics that should change the current planned treatment to something else that has been shown by randomized controlled trial to improve patient outcomes in similar patients?" Powers questioned.
Mark McGraw is a contributing writer.