Jessica Moore, PGY-1
Article: Gottlieb, Michael, et al. “Point‐of‐Care Ultrasound for the Diagnosis of Thoracoabdominal Injuries After Blunt Trauma.” Academic Emergency Medicine, vol. 26, no. 7, 2019, pp. 829–831., doi:10.1111/acem.13722.
Background: Trauma is a common reason for presentation to the emergency department, as well as a major cause of morbidity and mortality worldwide. The use of point-of-care ultrasound (POCUS) has become widespread in the initial evaluation of patients presenting after traumatic injury as it can help to identify both significant intrathoracic injury as well as intraabdominal free fluid. This bedside test is especially helpful when a patient is unstable or cannot undergo CT. This article assesses the diagnostic accuracy of this important and ubiquitous bedside test.
Study: This article discusses a Cochrane Review that assessed the diagnostic accuracy of POCUS for the identification of intrathoracic and intraabdominal injuries after blunt trauma. Thirty-four studies analyzing a total of 8,635 patients met criteria for inclusion in the meta-analysis; both retrospective and prospective studies were included. The primary outcome was diagnosis of any intrathoracic or intraabdominal injury by US as compared to a reference standard (CT, MRI, laparotomy, laparoscopy, thoracotomy, or autopsy).
Results: The review found that overall, POCUS was 74% sensitive and 96% specific for the identification of thoracoabdominal injury. When subgroup analysis was performed for adult and pediatric patients, POCUS was 63% sensitive and 91% specific for pediatrics versus 78% sensitive and 97% specific for adult patients in the identification of thoracoabdominal injury. When subgroup analysis was performed for intrathoracic and intraabdominal injury, POCUS was 68% sensitive and 95% specific for intraabdominal injury, compared to 96% sensitive and 99% specific for intrathoracic injury.
The authors projected an overall baseline pretest probability of thoracoabdominal injury of approximately 28% based on the prevalence of these injuries in included studies. Based on this statistic, the authors suggest POCUS would give an overall false positive rate of 2.9% and false negative rate of 7.3%. Both of these values increase in pediatric patients; with an estimated baseline pretest probability of thoracoabdominal injury of 31% in children, the authors suggest we would miss 11.8% of injuries and falsely diagnose injury in 6.2% of children.
A notable limitation of the review was the variation among studies regarding the performers’ specialties, levels of training, and amount of experience with POCUS. Such variation may lead to discrepancies in interpretation of the test, and therefore also the proper diagnosis of injury. It is also important to note that the study assessed for the identification of any intrathoracic or intraabdominal injury, and not just those that are life-threatening, those that require intervention, or those that can be identified by bedside ultrasound. The authors suggest that POCUS is intended to identify free fluid as a means for screening for intraabdominal injury, and that identification of any injury is beyond the scope and purpose of the POCUS in the acute trauma setting. Finally, this review does not comment on the accuracy of POCUS in the patient with acute penetrating trauma.
Takeaway: Overall, the benefits of performing point-of-care ultrasound outweigh associated harms in the patient with acute blunt trauma. POCUS is highly sensitive and specific for identification of intrathoracic injury; however, it is highly sensitive but not adequately sensitive for intraabdominal injury. Thus, a positive test strongly implies the presence of injury, however, intraabdominal injury cannot be ruled out with a negative POCUS. Lastly, POCUS has higher sensitivity and specificity for thoracoabdominal injury in adults as compared to pediatric patients.