Bypassing Clinical Decision Support Tools for Imaging in the ED

Hossein Jadvar, MD, PhD, MPH, MBA


April 20, 2017

The Study

Medical imaging is a major contributor to the diagnostic evaluation process and clinical decision-making in the emergency department (ED). In the ED, acute pulmonary embolism (PE) is a condition that requires accurate diagnosis and prompt treatment, and the Wells criteria are evidence-based decision tools that have been designed to assist with diagnostic evaluation.[1]

A new study by Zihao Yan and colleagues from the Brigham and Women's Hospital—a tertiary care, academic medical center in Boston, Massachusetts, with a busy ED (60,000 annual visits)—was the clinical setting for the determination of the frequency and diagnostic yield of computed tomography pulmonary angiography (CTPA) after the providers overrode the Wells criteria in the evaluation of suspected PE.[2]

The investigation included 2993 CTPAs in 2655 patients over an approximately 2.5-year period. The authors compared the diagnostic yield of the override group (563 CTPAs in patients with a Wells score of 4 or less and no D-dimer testing and 26 CTPAs in patients with Wells Score of 4 or less and normal D-dimer) with that of the adherent group (2404 CTPAs). The yield of acute PE was 4.2% in the override group and more than twice that rate, at 11.2%, in the adherent group. The odds of acute PE were 51.3% lower when providers overrode rather than followed the clinical decision support guidelines.


The objective of this investigation was to compare the consequence of not adhering to clinical decision support tool on the basis of the Wells criteria in the setting of suspected acute PE in the ED. The authors concluded that despite access to and use of clinical decision support guidelines at their institution, there is room for improvement in avoiding unnecessary CTPAs. The simple act of mandating D-dimer testing before CTPA may help in accomplishing this goal because acute PE is highly unlikely in patients with normal D-dimer levels (< 500 ng/mL).

The US government has advocated the use of clinical decision support tools and appropriate use criteria in order to improve quality of care and reduce cost.[3] Imaging is one cost center that has been targeted to adhere to these measures.[4]

The new study demonstrated quantitatively and objectively that adherence to guidelines in the diagnostic workup of patients with suspected PE is appropriate. Although following such guidelines captured most patients with acute PE, there remained a small number of patients diagnosed with acute PE on clinical grounds. However, in this group (25 of 589 CTPAs), none had PE if the D-dimer was assessed and was normal. Therefore, as the authors suggest, D-dimer testing must be included in the diagnostic algorithm of these patients, given its high negative predictive value.



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