Medical Imaging Stewardship and Healthcare Savings: Utilization of Age Adjusted D-Dimer to Rule Out Acute Pulmonary Embolism.

Introduction: Acute pulmonary embolism (PE) is a common diagnosis that can lead to death if left untreated. Computerized tomography pulmonary angiogram scan (CTPA) is the gold standard for diagnosis of PE. Utilization of CTPA is increasing in the emergency setting even when suspicion for PE is very low. While CTPA is helpful, radiation exposure, contrast reactions, and cost must be considered. D-dimer is a well-established, high sensitivity and low specificity laboratory test that can effectively rule out PE in low-risk patients when negative. The ADJUST-PE trial showed that there is a natural rise of D-dimer levels with age. This age adjusted D-dimer level is meant to prevent unnecessary CTPA exams in low suspicion patients. We hypothesize that there are a significant amount of unwarranted CTPA exams ordered at our community hospital that would not have been performed if the age adjusted D-dimer level were implemented. Methods: During a four-month period we collected a list of patients 18 years of age and older who received a CTPA exam for initial evaluation of possible acute PE at our institution. The primary outcome was to evaluate the percentage of patients who received an imaging study despite a negative D-dimer collected prior to the study, using the age adjusted upper limit of normal based on the ADJUST-PE study. Results: There were 734 CTPA exams that met our criteria in a four-month period. D-dimer levels were checked in 30.38% (223 of 734) of cases prior to imaging. Out of these 223 cases, 21.08% (47 of 223) were found to have negative age adjusted D-Dimer levels yet still received an imaging study. Out of these 47 cases, 44% (21 of 47) would have been positive using the traditional D-dimer threshold. Conclusion: This study demonstrates that by adherence to the guideline-based pre-test algorithm and also utilizing the recommendations set forth by the ADJUST-PE study, approximately 21% of patients who undergo D-dimer testing would avoid unwarranted CT imaging. In addition to decreased radiation and contrast exposure, a significant amount of health care expense would be saved.