FAST versus F-AST Score (FAST plus Aspartate Transaminase) in Pediatric Blunt Abdominal Trauma — a Case Series Analysis

The use of focused assessment with sonography for trauma (FAST) examination in pediatric blunt abdominal trauma (BAT) has not been well accepted because of its poor sensitivity. We aim to determine whether the FAST combined with elevated liver enzymes, i.e., aspartate transaminase (AST), could be used as a better screening tool for intra-abdominal injury (IAI) in pediatric BAT and develop a new prediction model. A case series analysis was performed among pediatric patients (age < 18 years) with BAT, presenting to a level-1 trauma center. Data on patient demographics, vital signs, mechanism of injury, FAST finding, contrast-enhanced computed tomography (CECT) scan of the abdomen, and serum AST levels, were collected. Multiple logistic regression (MLR) was used to develop a prediction model for IAI. Overall, 499 children were identified. FAST was positive in 72 patients, whereas 69 patients had IAI in a CECT. FAST alone had a sensitivity of 76.8%. FAST examination’s negative predictive value (NPV) and negative likelihood ratio (NLR) were 95.8% and 0.24, respectively. Combining FAST and AST levels led to an increase in sensitivity to 91.3%, NPV to 97.9%. The NLR decreased to 0.1, which was clinically more relevant. In the MLR model, the odds ratios for the presence of IAI were significant for FAST and AST levels. Hence, FAST and AST levels were included in the new ‘F-AST score’. A score of one was assigned for FAST positive and zero for FAST negative. AST level < 90 U/L was assigned a score of zero and > 90 U/L as one. Aggregate F-AST score ranged from 0 to 2. The receiver’s operating characteristics (ROC) analysis showed the F-AST score to be very accurate with an area under the ROC curve of 0.905. Pediatric patients with a F-AST score of 0 (negative FAST and AST < 90 U/L) may be observed rather than subjected to CT scan radiation risk.