Assessment of the FAST Exam in Detecting Injuries in Patients With Blunt Trauma

Although emergency clinicians commonly use the Focused Assessment with Sonography for Trauma (FAST) exam to detect free fluid as a proxy for the presence of intraabdominal injury, there is little data regarding its screening characteristics. In a multicenter cohort of adult blunt trauma patients, we sought to determine the screening performance of the FAST for detecting these injuries.

This secondary analysis of prospectively collected data from the North American X-ray Utilization Study (NEXUS) abdominal/pelvis CT cohort study at 4 trauma centers included 3,377 blunt trauma patients who received both a FAST and abdominal/pelvis CT with contrast. Prior to the study, a panel of surgeons, EM physicians, and radiologists classified injuries as major (needing surgery or transfusion), minor (requiring observation), and clinically insignificant (no intervention or observation). With blindly abstracted reviews of ED/hospital records for injury classification, we calculated the sensitivity, specificity, PPV and NPV of a positive FAST exam for major, minor and clinically insignificant abdominal/pelvic injury.

Of 3,377 patients, there were 151 positive FAST. For major abdominal/pelvic injuries, the FAST Exam had a sensitivity of 12% (95% CI 9-16%), specificity of 96% (CI 96-97%), PPV of 23% (CI 17-31%) and NPV of 92% (CI 91-93%). For major or minor injuries, it had a sensitivity of 10 (CI 8%-13%), specificity of 97% (CI 96-97%), PPV of 34% (CI 27-42%) and NPV of 86% (CI 84-87%). For any injury, it had a sensitivity of 9% (CI 7-12%), specificity of 97% (CI 96-97%), PPV of 39% (CI 32-47%) and NPV of 82% (CI 81-83%).

The FAST exam demonstrated high specificity but poor sensitivity for major and minor intraabdominal injury. A positive FAST exam is highly indicative of intraabdominal injury but a negative exam does not rule it out.