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Abstract #152821

Bahman Roudsari, MD MPH PhD, Epidemiology, University of Texas School of Public Health, 5323 Harry Hines, V8.112, Dallas, TX 75390-9128, 214-648-1054, bahman.roudsari@utsouthwestern.edu, Raymond Fowler, MD, Emergency Medicine, University of Texas, Southwestern Medical School, 5323 Harry Hines, Dallas, TX 75390-8890, and Avery Nathens, MD MPH PhD, Surgery, St. Michael's Hospital, 30 Bond St., Toronto, ON M5B 1W8, Canada.

Introduction: Design of a clustered childhood trauma study requires having an estimate of the variability in the outcome of interest between and within the clusters. “Intracluster correlation coefficient (ICC)” is a standard measure that captures these variabilities. However, ICC has not been reported for any childhood-related trauma outcome. Methods: We used the data from 246 level I and II trauma centers contributed data to the United States, National Trauma Data Bank to calculate the ICC of emergency department (ED) shock rate, early trauma death (i.e. death during the first 24 hours after admission) and in-hospital trauma death for children ≤ 15 years old. These outcomes are used for the evaluation of prehospital and hospital trauma care. Results: From 2000 to 2004, 13% of the 952,242 patients in NTDB were ≤ 15 years old . Approximately 17,000 of these children suffered severe injuries, of them 84% were hospitalized at a level I or II trauma center. In general, the ICC for ED shock rate (0.005, 95% CI: 0.000-0.010) was significantly less than the ICC for in-hospital trauma fatality rate (0.023, 95% CI: 0.013-0.033). A similar pattern was observed when we compared the ICC of ED shock rate with the ICC of in-hospital trauma fatality rate for different genders or types of injury. Conclusion: Clustered childhood trauma studies that aim at comparison of different aspects of prehospital and hospital trauma care should incorporate these ICCs for sample calculation.

Learning Objectives:

• Multicenter trauma studies are becoming more common, due to the availability of large trauma registries.
• Due to some measured and unmeasured characteristics such as distribution of age, sex, type and mechanism of injury, socioeconomic status and quality of hospital and prehospital care, patients outcome within clusters tend to be more similar than the patients outcome among different clusters.
• Due to this dependency of the outcome within clusters, standard sample size calculation formula that do not capture variability in the outcome of interest at the cluster level, provide artificially low sample sizes.
• In order to calculate correct sample size for clustered studies, Intracluster Correlation Coefficient (ICC) for the outcomes of interest should be calculated.
• This study is the first study that has reported ICCs for three of the most commonly used outcomes of interest in childhood injuries

Keywords: Injury, Epidemiology

Presenting author's disclosure statement:

Any relevant financial relationships? No
Any institutionally-contracted trials related to this submission?

I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.