50 Multi-Center Implementation of Automated Age-Adjusted D-Dimer Cutoffs Reduces Unnecessary CTPE Imaging

Abstract

Several previous studies have investigated the clinical utility of age-adjusted d-dimer cutoffs demonstrating that it is more specific but less sensitive than conventional cutoffs for diagnosing pulmonary embolism (PE). We performed a pre/post implementation study, using data from a mid-Atlantic health care system comprising 6 hospitals and 400,000 ED visits to determine whether implementing age adjusted d-dimer cutoffs reduced the number of imaging tests ordered. Retrospective study of d-dimer orders from emergency department visits dating March 2016 to May 2018. As of March 2017, the upper limit of normal for d-dimer testing system wide was increased for patients over 50 to: Age(years) x .01mg/L. D-dimer results were displayed as normal or high based on automated age adjustment. EHR chart review was performed one year prior to implementation of age-adjusted d-dimer cutoffs, as well as one year after. Comparisons were made using chi-square testing. 11310 d-dimers were ordered pre-implementation with 6736 resulting positive compared to 14342 ordered and 7416 positive post-implementations (pre: 59.6%, post: 51.7%; p<0.05). Patients with positive d-dimer results had 4069 CTPE studies performed pre-implementation and 4942 were performed post-implementation. A significantly lower proportion of patients underwent CT-imaging post-implementation: 4942/14342 (34.5%) versus 4069/11310 (36.0%); p=0.01. This absolute risk reduction of 1.5% is associated with 215 (4.4%) less CT scans in the post-implementation group. 105 of the 1377 (7.6%) patients with a newly-negative d-dimer had a CT performed anyway with 2 scans revealing pulmonary embolism (segmental). There were 7 patients in the newly negative group with <30-day mortality clearly documented as not related to pulmonary embolism. Automated age-adjusted d-dimer result implementation reduced unnecessary CT imaging system wide by 4.4% without adversely affecting safety endpoints.