Comparison of revised Functional Capacity Index scores with Abbreviated Injury Scale 2008 scores in predicting 12-month severe trauma outcomes

Introduction: Anatomical injury as measured by the AIS often accounts for only a small proportion of variability in outcomes after injury. The predictive Functional Capacity Index (FCI) appended to the 2008 AIS claims to provide a widely available method of predicting 12-month function following injury. Objectives: To determine the extent to which AIS-based and FCI-based scoring is able to add to a simple predictive model of 12-month function following severe injury. Methods: Adult trauma patients were drawn from the population-based Victorian State Trauma Registry. Major trauma and severely injured orthopaedic trauma patients were followed up via telephone interview including Glasgow Outcome Scale - Extended, the EQ-5D-3L and return to work status. A battery of AIS-based and FCI-based scores, and a simple count of AIS-coded injuries were added in turn to a base model using age and gender. Results: A total of 20 813 patients survived to 12 months and had at least one functional outcome recorded, representing 85% follow-up. Predictions using the base model varied substantially across outcome measures. Irrespective of the method used to classify the severity of injury, adding injury severity to the model significantly, but only slightly improved model fit. Across the outcomes evaluated, no method of injury severity assessment consistently outperformed any other. Conclusions: Anatomical injury is a predictor of trauma outcome. However, injury severity as described by the FCI does not consistently improve discrimination, or even provide the best discrimination compared with AIS-based severity scores or a simple injury count.