INTERPRETATION OF THE WS STATISTIC - APPLICATION TO AN INTEGRATED TRAUMA SYSTEM

Background: Comparison of trauma survival rates between institutions a nd reference data bases is hampered by different injury severity mixes , To overcome this, a standardized comparison using a stratified W sta tistic (Ws) has been proposed, Ws enables comparisons but does not rep resent actual survival rates at an institution. Method, Discussion, an d Results: This discussion paper uses, as an example, data from 632 pa tients with blunt injuries treated by an integrated trauma system comp rising a helicopter emergency medical service and the Royal London Hos pital, Using the United Kingdom Major Trauma Outcome Study as a refere nce data set, Wa is calculated and its usefulness discussed, The probl em of overprediction of survival is discussed, A modification of the W s method is used to allow for this and to estimate the actual survival rate. Conclusion: Ws is useful for comparison between centers, Trauma and Injury Severity Score methodology overpredicts survival in certai n probability of survival intervals, Adjustment can be made to estimat e the actual survival rate, When applied to an integrated trauma syste m, such adjustments demonstrate overall improved survival, most notice able in a more severely injured subgroup.