ED Use of D-dimers for the Diagnosis of VTE

Abstract

PURPOSE:To determine the use of D-dimers in the diagnostic approach to patients presenting to the emergency department (ED) with suspected venous thromboembolism (VTE). METHODS:We performed a retrospective chart review of all adult patients presenting to the ED of the Jewish General Hospital (Montreal, Canada) between March 23 rd and April 3 rd , 2015 and had a high sensitivity D-dimer requested. Patients evaluated for non-VTE conditions were excluded. For all included patients, we determined if a Wells score prior to D-dimer requisition was recorded. For patients without a documented Wells score, we calculated the Modified Wells score based on data from the ED physician's initial history and physical exam. We determined diagnostic imaging following D-dimer in all patients. RESULTS:Among 141 patients with a D-dimer for VTE assessment, 9 (6.4%) had a documented Wells score, 10 (7.1%) had sufficient data to calculate a score, and 122 (86.5%) had neither a recorded score nor sufficient data. All 9 patients with a documented score had a low/moderate risk score, and the D-dimer was positive in 5 (55.6%) and negative in 4 (44.4%). All 10 patients with a calculated score had a low/moderate risk score, among whom 3 (30%) had a positive D-dimer and 7 (70%) had a negative D-dimer. Among the patients with a recorded or calculated score, diagnostic imaging was performed in none of the patients with a negative D-dimer and in 5 (62.5%) patients with a positive D-dimer. Among the group of patients without a recorded or calculated score, 49 (40.2%) had a positive D-dimer among whom 30 (61.2%) had imaging and 73 (59.8%) had a negative D-dimer among whom 6 (8.2%) had diagnostic imaging. CONCLUSIONS:In our study, only 6% of patients presenting to the ED with suspected VTE had a prediction rule calculated prior to D-dimer requisition. In addition, low/moderate risk score patients with a positive D-dimer did not always undergo diagnostic imaging. Physician use of D-dimers for VTE assessment is not in keeping with guideline recommendations.CLINICAL IMPLICATIONS: Guideline recommendations suggest that the initial assessment for VTE include risk stratification. Low/moderate risk patients should have a D-dimer. A negative result reliably excludes the presence of VTE in this population, eliminating the need for imaging. Elimination of inappropriate imaging would improve resource allocation and reduce patient harm (eg, radiation exposure). Conversely, D-dimers are not indicated in high risk patients. Negative results in this population carry a significant false negative risk. This may lead to patient morbidity/mortality from a missed VTE if imaging is not pursued. Similarly, low/moderate risk patients with a positive D-dimer should undergo imaging to avoid missing a VTE.