What is the difference between Extended Focused Assessment with Sonography for Trauma (EFAST) and Focused Assessment with Sonography for Trauma (FAST)?

EFAST vs FAST: Key Differences

EFAST (Extended FAST) adds thoracic views to the standard FAST examination, specifically evaluating for pneumothorax and hemothorax in the pleural spaces, while traditional FAST focuses solely on detecting free fluid in the pericardial and peritoneal cavities. 1

Standard FAST Examination

Traditional FAST is a focused, goal-directed sonographic examination that evaluates only:

• Pericardial space for hemopericardium (subxyphoid cardiac view) 1
• Peritoneal cavity for hemoperitoneum in trauma patients with signs of shock or suspected abdominal injury 1

The primary goal is detecting free fluid collection in body cavities to make rapid life-saving decisions. 1

Extended FAST (EFAST) Examination

EFAST expands the standard FAST by adding bilateral thoracic evaluation:

• All standard FAST views (pericardial and peritoneal spaces) 1
• Bilateral pleural spaces to detect hemothorax 1, 2
• Lung parenchyma to identify pneumothorax 1, 2

This integration allows EFAST to detect pleural fluid and pneumothorax in addition to the traditional FAST findings. 1

Clinical Performance and Utility

For hemodynamically unstable patients, EFAST combined with chest X-ray enables appropriate urgent intervention decisions with 98% accuracy. 2, 3

Diagnostic Performance Metrics:

• Positive predictive value of 97% for intra-abdominal bleeding in pelvic trauma with severe abdominal trauma 2
• Negative predictive value of 97% in patients with shock 2, 3
• Specificity of 91-100% across all components 4
• Sensitivity varies significantly by component and clinical scenario 5, 6, 4

Critical Limitations of EFAST for Pneumothorax Detection

EFAST has poor sensitivity (22-43%) for detecting pneumothorax in real-world trauma settings, though specificity remains high. 5, 6, 4, 7

Specific Pneumothorax Detection Issues:

• Missed pneumothoraces are typically smaller (mean 6.9-12.1 mm vs 30.2-30.7 mm for detected ones) 7
• Apical and basal pneumothoraces are frequently missed (34.9% and 41.9% of missed cases respectively) compared to ventral locations 7
• Only 30% of missed pneumothoraces required chest tube compared to 88.9% of those detected by EFAST 7
• Sensitivity improves to 81% for pneumothoraces requiring treatment 7

Clinical Decision Algorithm

In hemodynamically unstable patients:

• Perform EFAST immediately during resuscitation alongside chest and pelvic X-rays 1, 3
• When EFAST and chest X-ray rule out extra-pelvic hemorrhage sources, proceed directly to angiography/embolization 2, 3
• Do not delay life-saving interventions to obtain additional imaging 1

In hemodynamically stable patients:

• Perform EFAST as initial rapid assessment 1, 2
• Proceed directly to CT scan with IV contrast for complete injury inventory 3
• Do not delay CT to obtain additional plain films 3

Common Pitfalls to Avoid

False positives occur with:

• Hemoretroperitoneum suffusion appearing as intraperitoneal fluid 2, 3
• Intraperitoneal bladder rupture mimicking hemoperitoneum 2, 3

False negatives are common for:

• Pancreatic injuries - EFAST is not recommended for diagnosing duodeno-pancreatic trauma 2, 8
• Bowel injuries - frequently missed by EFAST 8
• Small or atypically located pneumothoraces 7
• Retroperitoneal hemorrhage - cannot be reliably detected 1

A negative EFAST does not rule out:

• Significant intra-abdominal injury requiring intervention 1
• Slowly accumulating free fluid if performed very early 1
• Solid organ injuries without significant hemoperitoneum 1