Effect of computerized clinical decision support on the use and yield of CT pulmonary angiography in the emergency department

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"Purpose: To determine the effect of evidence-based clinical decision support (CDS) on the use and yield of computed tomographic (CT) pulmonary angiography for acute pulmonary embolism (PE) in the emergency department (ED). Materials and Methods: Institutional review board approval was obtained for this HIPAA-compliant study, which was performed between October 1, 2003, and September 30, 2009, at a 793-bed quaternary care institution with 60000 annual ED visits. Use (number of examinations per 1000 ED visits) and yield (percentage of examinations positive for acute PE) of CT pulmonary angiography were compared before and after CDS implementation in August 2007. The authors included all adult patients presenting to the ED and developed and validated a natural language processing tool to identify acute PE diagnoses. Linear trend analysis was used to assess for variation in CT pulmonary angiography use. Logistic regression was used to determine variation in yield after controlling for patient demographic and clinical characteristics. Results: Of 338 230 patients presenting to the ED, 6838 (2.0%) underwent CT pulmonary angiography. Quarterly CT pulmonary angiography use increased 82.1% before CDS implementation, from 14.5 to 26.4 examinations per 1000 patients ( P , .0001) between October 10, 2003, and July 31, 2007. After CDS implementation, quarterly use decreased 20.1%, from 26.4 to 21.1 examinations per 1000 patients between August 1, 2007, and September 30, 2009 (P = .0379). Overall, 686 (10.0%) of the CT pulmonary angiographic examinations performed during the 6-year period were positive for PE; subsequent to CDS implementation, yield by quarter increased 69.0%, from 5.8% to 9.8% (P = .0323). Conclusion: Implementation of evidence-based CDS in the ED was associated with a significant decrease in use, and increase in yield, of CT pulmonary angiography for the evaluation of acute PE. ©RSNA, 2011"[1]


  • Computed Tomography (CT) is a form of imaging based on the variable absorption of x-rays by different tissues, it provides a different type of images known as cross-sectional imaging. The images obtained are in the axial plain and are a representation of "slice" of anatomy.[2]
  • Computed Tomography Angiography (CTA) is a type of medical exam that combines a CT scan with an injection of contrast media to produce images of blood vessels and tissues in a part of your body. The contrast is injected through an intravenous (IV) line started in your arm or hand. [3]
  • Pulmonary Embolism (PE) is a blockage in one of the pulmonary arteries in the lungs. In most cases, pulmonary embolism is caused by blood clots that travel to the lungs from the legs or, rarely, other parts of the body (deep vein thrombosis). [4]


This research study was done in order to see the impact a CDS tool had on the ordering of CT pulmonary angiograms for pulmonary embolisms in the emergency department.

Materials and methods

The authors developed and tested a natural language algorithm to search through radiology reports to find positive and negative pulmonary embolism results. The CDS tool was based on 3 rules that had been previously developed along with collaboration between faculty at the hospital.


Prior to implementation of the CDS tool, the CT pulmonary angiogram use increased by 82.1% over an almost 4 year period. However, after the CDS tool was deployed, the CT pulmonary angiogram use decreased quarterly by 20.1% over approximately a two year period. The natural language algorithm was found to have a sensitivity of 91.3% and a specificity of 98.7%.


The results of similar studies vary compared to the positive findings of this article. This may be due to difficulty getting ED physicians to adhere to the guidelines suggested by the CDS tool according to a previous study. The authors of the article I reviewed felt they had better adherence due to involvement of more faculty at meetings and an education campaign towards evidence based medicine used by the CDS tool.


This article shows that with careful planning and collaboration with all parties involved, a CDS tool can have a positive impact on CT pulmonary angiography in the ED.

The importance of ensuring that only patients that meet criteria for this exam are scheduled for it is the radiation dose and contrast media administration risks. The radiation dose for a CTA is approximately 12 mSv which is comparable to 4 years to natural background radiation exposure and the estimated lifetime risk of fatal cancer from examination is low (1 in 10,000 to 1 in 1000).[5] Clinical decision support is a valuable tool for physicians in the fast, chaotic emergency department in which decisions may be the difference between life and death.


  1. Raja, A. S., Ip, I. K., Prevedello, L. M., Sodickson, A. D., Farkas, C., Zane, R. D., … Khorasani, R. (2012). Effect of Computerized Clinical Decision Support on the Use and Yield of CT Pulmonary Angiography in the Emergency Department. Radiology, 262(2), 468. http://doi.org/10.1148/radiol.11110951
  2. What is Computed Tomography? http://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm115318.htm
  3. Computed Tomography Angiography (CTA)http://www.hopkinsmedicine.org/healthlibrary/test_procedures/cardiovascular/computed_tomography_angiography_cta_135,15/
  4. Pulmonary embolism http://www.mayoclinic.org/diseases-conditions/pulmonary-embolism/basics/definition/con-20022849
  5. Radiation Dose in X-Ray and CT Exams http://www.radiologyinfo.org/en/info.cfm?pg=safety-xray