Using multiple imputation and propensity scores to test the effect of car seats and seat belt usage on injury severity from trauma registry data

BackgroundMissing data and the retrospective, nonrandomized nature of trauma registries can decrease the quality of registry-based research. Therefore, we used multiple imputation and propensity scores to test the effect of car seats and seat belt usage on injury severity in children involved in motor vehicle crashes.MethodsAll children admitted after injury from motor vehicle crashes who had complete data on seat belt or car seat usage from 2003 to 2006 were included in the study. The sample was divided into children younger than 4 years (n = 130) or 5 years or older (n = 575) and analyzed for seat belt usage, car seat usage, injury severity score, revised trauma score, and Glasgow Coma Scale score. Data were analyzed before and after matching on propensity scores after multiple imputation.ResultsThere were no outcome differences between car seat users and non–car seat users. However, there were significant improvements in injury severity score (7.0 vs. 10.1, P = .002) and revised trauma score (7.6 vs 7.3, P = .013 for seat belt users compared to nonusers) even after matching on propensity score.ConclusionMultiple imputation and propensity scores demonstrated the efficacy of seat belts, but not car seat in this preliminary study. This statistical method can strengthen registry-based research.