Abstract
Objective: To evaluate what specific combination of clinical criteria and d-dimer values may yield at least a 10% positive pulmonary embolism (PE) rate in patients undergoing pulmonary CT angiography (CTA). Materials and Methods: Retrospective review of all patients presenting to the Emergency Department with possible PE who underwent pulmonary CTA and had a d-dimer drawn. Wells scores were retrospectively assigned based on data gathered through medical records. Results: During a 29-month period, 1110 patients underwent pulmonary CTA. Of these, 773 also had a d-dimer drawn. These subjects were stratified based on serum d-dimer levels into negative (≤4 μg/ml), nonpositive (0.41 - 1.0 μg/ml), or positive (>1.0 μg/ml) d-dimer categories. The prevalence of positive CTA studies was >10% only in the positive d-dimer group. Subjects were also stratified based on their Wells score into three clinical categories: low (score 2), intermediate (score = 2 - 6), and high risk of pulmonary embolism (score > 6). The prevalence of positive CTA was > 10% only in the group of subjects with high clinical risk. When stratified according to both Wells criteria and d-dimer, only those patients with intermediate or high clinical risk combined with a positive d-dimer (>1.0 μg/ml) had a prevalence of positive pulmonary CTA > 10%. By limiting the use of CTA studies to those patients with positive d-dimer values or high clinical risk, 438 (55.4%) patients could have avoided CTA imaging. Conclusion: Utilizing CTA only in patients suspected of PE with a combination of high clinical risk based on a Wells criteria threshold score > 6 and a serum d-dimer cutoff of 1 μg/ml would increase the prevalence of positive pulmonary CTA studies above 10% and avoid a large number of CTA imaging studies.
Highlights
The evaluation and management of patients suspected of acute pulmonary embolism (PE) in the emergency department setting is evolving
Utilizing CT angiography (CTA) only in patients suspected of PE with a combination of high clinical risk based on a Wells criteria threshold score > 6 and a serum d-dimer cutoff of 1 μg/ml would increase the prevalence of positive pulmonary CTA studies above 10% and avoid a large number of CTA imaging studies
During the 29 months from January 2007 through May 2009, 1110 patients seen by the Emergency Medicine Department with suspected PE underwent pulmonary CTA
Summary
The ready availability of multidetector row CT scanners and quantitative serum d-dimer assays with rapid turnaround times have changed physician attitudes toward PE. It seems that physicians are much more likely to entertain the diagnosis of acute PE in their patients and to order tests . With the increasing ease of diagnosis, it is becoming clear that pulmonary CT angiography (CTA) is over utilized [1,2]. Studies have yet to demonstrate that this increased utilization of pulmonary CTA significantly decreases patient morbidity or mortality associated with PE, a disease whose incidence, prevalence and natural history is poorly understood [3].
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