62 Trends in Use of Chest Computed Tomography With Angiography for Diagnosis of Pulmonary Embolism

Abstract

Study Objectives: Reduction of CT scan radiation is a public health mandate. As an internal quality marker, we determined that our ordering rate for CT angiograms of the chest was 164 out of 38701 patients (0.42%) in 2006 and 276 out of 41398 patients (0.67%) in 2010, an increase of 59%. We aimed to determine if our incidence of scans positive for pulmonary embolism also changed. Methods: All patients ages 18 and older who were seen in our emergency department (ED) and who had a CT angiograms chest ordered in either 2006 or 2010 were eligible for inclusion. Patients were excluded if their CT scan was canceled or for another indication. The characteristics and test results of the 2 cohorts were compared. Additionally, the PERC rule was applied retrospectively to determine if scans could have been avoided, with the understanding that these were not necessarily low-risk patients. Results: One hundred twenty-four patients met study criteria in 2006 and 217 in 2010. There were no differences in sex (p=0.53). Mean age was younger in the 2006 cohort (42.9 yrs (95% CI 39.9-45.9) versus 49.8 yrs (95% CI 47.5-52.0), p=0.002). There were no differences in pulse rate (p=0.08), respiratory rate (p=0.52), temperature (p=0.23), systolic BP (p=0.13) or O2 saturation (p=0.97). Patients in the 2006 cohort were more likely to have a history of prior clot (27.1% versus 18.0%, p=0.05) and use estrogen (9.0% versus 3.7%, p=0.04), but there were no differences in history of recent surgery (10.7% versus 12.0%, p=0.71), recent immobilization (8.2% versus 7.4%, p=0.79), hemoptysis (1.6% versus 2.8%, p=0.51), history of cancer (14.8% versus 18.4%, p=0.38) or presence of DVT clinically (21.3% versus 16.1%, p=0.23). The positive scan rate was 11.3% (14/124) in 2006 and 11.5% (25/217) in 2010, p=0.95, indicating no change in the positive scan rate but a large increase in incidence of the disease in our patient population. Combining both cohorts, 219/341 patients (62.4%) had d-dimer testing. 18/173 (10.4%) patients with a positive d-dimer had pulmonary embolism. 1/46 (2.2%) patients with negative d-dimer had pulmonary embolism. Retrospectively applying the PERC rule to our cohort, 0/59 (0%) patients who met all PERC low-risk criteria had pulmonary embolism (p=0.002). Conclusion: The increased rate of CT angiograms chest testing in our ED appears to be justified by the fact that our rate of scans positive for pulmonary embolism is unchanged. However, the incidence of the diagnosis as a proportion of total patient population increased markedly during this time; this concerning finding warrants further study.