The diagnostic yield of alternative findings on computed tomography for pulmonary embolism

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Conference Proceeding

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Academic emergency medicine


Background and Objectives: Computed tomography pulmonary angiogram (CTPA) is being used increasingly to diagnose pulmonary embolism (PE) in the ED, even in patients with low or moderate risk. The Michigan Emergency Department Improvement Collaborative (MEDIC) has identified reduction of inappropriate CTPA utilization as a goal for member EDs. Some have speculated that the ability of CTPA to identify other non-PE (“alternative”) diagnoses may justify the widespread use of this modality. We hypothesized that CTPA would have a low diagnostic yield for conditions other than acute PE in the ED setting.

Methods: Review of the MEDIC quality improvement database was performed, including data collected over an 8-month period (1 January 2019 to 31 August 2019) from the 19 MEDIC member hospitals. Data on patient demographics, d-dimer values, CTPA diagnostic findings, ED disposition, and survival to ED disposition were extracted for all patients who received CTPA to rule out PE in the ED.

Results: A total of 15,811 CTPA studies were included, with a mean patient age of 62.6 years (SD 16.4) and 60.4% were female. D-dimer level was obtained in 7,226 (45.7%) cases, and was positive in 6832 (43.2%) cases. In fact, d-dimer was positive in 94% of all cases in which it was ordered. In all, 1,447 (9.2%) CTPA scans were positive for acute PE. No pathologic finding was identified in 9,024 (62.8%) of PE-negative CTPA studies. The most common “alternative” diagnoses on CTPA were pneumonia (1,385 [9.6%]), pleural effusion (1,287 [9.0%]), and malignancy (610 [4.3%]). Chronic PE was identified in 126 (0.9%) patients.

Conclusion: The diagnostic yield of CTPA for acute PE in this study was 9.2%, consistent with reports by other groups. The diagnostic yield for non-PE conditions was 37.2%, with more than half of these alternative CTPA findings classified as pneumonia or pleural effusions, both conditions that might be expected to be visible on simple chest radiograph. The chronicity of these findings could not be determined from the data collected. Additional research is needed to determine whether such “alternative” findings on CTPA lead to new diagnoses or change clinical management for ED patients with suspected acute PE.



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