CT pulmonary angiography (CTPA) is considered the gold standard for the diagnosis of pulmonary embolism (PE) and is frequently performed in patients with cardiopulmonary complaints. However, indiscriminate use of CTPA results in significant exposure to ionizing radiation and contrast. We studied the accuracy of a bedside ultrasound protocol to predict the need for CTPA.
This was an observational study performed by pulmonary/critical care physicians trained in critical care ultrasonography. Screening ultrasonography was performed when a CTPA was ordered to rule out PE. The ultrasound examination consisted of a limited ECG, thoracic ultrasonography, and lower extremity deep venous compression study. We predicted that CTPA would not be needed if either DVT was found or clear evidence of an alternative diagnosis was established. CTPA parenchymal and pleural findings, and, when available, formal DVT and ECG results, were compared with our screening ultrasound findings.
Of 96 subjects who underwent CTPA, 12 subjects (12.5%) were positive for PE. All 96 subjects had an ultrasound study; two subjects (2.1%) were positive for lower extremity DVT, and 54 subjects (56.2%) had an alternative diagnosis suggested by ultrasonography, such as alveolar consolidation consistent with pneumonia or pulmonary edema, which correlated with CTPA findings. In no patient did the CTPA add an additional diagnosis over the screening ultrasound study.
We conclude that ultrasound examination indicated that CTPA was not needed in 56 of 96 patients (58.3%). A screening, point-of-care ultrasonography protocol may predict the need for CTPA. Furthermore, an alternative diagnosis can be established that correlates with CTPA. This study needs further verification, but it offers a possible approach to reduce the cost and radiation exposure that is associated with CTPA.