No abstract

pulmonary embolism (PE) as defined as a Traditional Well's score of less than two, a modified Wells score of less than or equal four, or a Revised Geneva Score (RGS) of three or less. The primary goal of this pilot study was to determine the incidence of missed PE diagnosed by computed tomography pulmonary angiography (CTPA) in patients undergoing evaluation for PE with a quantitative d-dimer assay of 0.5-1.0 mg/ L and a low-risk pre-test probability. The secondary goal of the study was to determine whether adjusted pre-test probabilities and reduced CT scans would result in missed diagnoses of pneumonia in this patient population.Methods: Participants: All patients older than 18 years of age being evaluated for pulmonary embolism with a d-dimer result between 0.5 and 1.0 mg/L during emergency department evaluation between the dates of January 1, 13 and June 14, 14 at a tertiary academic hospital. Design: A retrospective chart review was completed on all patients meeting primary inclusion criteria. The patients were retrospectively stratified based on traditional Well's scoring system, Modified Well's, and RGS. Patients in which pre-test probability was determined to be low (<2 by traditional Wells, 4 by modified Wells, or <4 by RGS), a d-dimer result of 0.5-1.0 mg/L, and who underwent definitive imaging for pulmonary embolism in the emergency department were selected for inclusion in the study analysis. Analysis: The incidence of missed PE in patients with low pretest probability as well the incidence of pneumonia in each scoring system was determined.Results: After reviewing 2231 eligible patient records for inclusion criteria, 46 patients were included for final analysis. For patients evaluated for PE with diagnostic imaging who had an intermediate d-dimer (0.5-1 mg/L) and a non-elevated bi-level modified Wells score (<4), 2 patients (4.34%) were ultimately diagnosed with PE by CTPA. When using either traditional low-risk Well's or RGS scores in patients with an intermediate d-dimer, no patients were found to have PE (0/42 and 0/21, respectively). Pneumonia was found by CTPA in 4/46 patients in the non-high modified Wells score range (8.7%), and in 4/42 (8.34%) of patients in the low risk Wells range. Pneumonia was found by standard chest x-ray in each of these patients.Conclusions: This pilot study suggests that increasing the threshold for a positive d-dimer to 1.0 mg/L in conjunction with a low pre-test probability as defined by traditional Wells score of less than two could be used to exclude PE with 100% negative predictive value while simultaneously reducing the use of CTPA and exposure to ionizing radiation in the emergency department. Further study with an increased number of patients meeting inclusion criteria needs to be performed before widespread adoption of this diagnostic algorithm can be considered as the sole exclusion in patients being evaluated for PE in the emergency department.