Is the FAST exam reliable in severely injured patients?

Highly sensitive and accurate for the detection of injuries requiring intervention in haemodynamically unstable patients, FAST may underestimate intra-abdominal injuries in stable patients with blunt abdominal trauma. Diminished accuracy of ultrasound has been reported in different cohorts of multiple injured patients. We hypothesised that multiple injured patients with a high Injury Severity Score (ISS) will have a decreased accuracy of FAST for the assessment of blunt abdominal trauma.

Data from the trauma registry of a Level 1 trauma centre were retrospectively reviewed. All haemodynamically stable blunt trauma patients who underwent both FAST and CT scan of abdomen from January 1, 2000 to January 1, 2005 were included in the cohort. All patients were divided into three groups according to their ISS: Group 1 included patients with an ISS from 1 to 14, Group 2 included patients with an ISS from 16 to 24, and Group 3 consisted of patients with ISS>or=25.

3181 patients with blunt abdominal trauma included into the study were divided into the three groups according to the ISS. The mean ISS was 7.9+/-3.97, 19.6+/-2.48 and 41.3+/-11.95 in Groups 1, 2 and 3, respectively. The accuracy of ultrasound was 90.6% in the group of patients with the highest ISS (>or=25) compared with 97.5 and 97.1 for Groups 1 and 2 (p<0.001). Similarly, ultrasound had a significantly lower sensitivity, specificity, PPV and NPV for patients in Group 3 compared with the first two groups (p<0.001). There was a significantly lower sensitivity in Group 2 compared with Group 1 (p<0.001), but no differences in specificity, accuracy, PPV or NPV were demonstrated.

Patients with high ISS are at increased risk of having ultrasound-occult injuries and have a lower accuracy of their ultrasound examination than patients with low and moderate ISS.