Performance of ICD-10-based injury severity scores in pediatric trauma patients using the ICD-AIS map and survival rate ratios

Objective: The performance of injury severity scores, used widely to quantify injury severity and predict outcomes, has not been investigated in German pediatric cases. This study aims to identify the most feasible and accurate injury score predictor of mortality in German children with trauma using International Classification of Diseases 10 (ICD-10).

Study design and setting: Between 2014 and 2020, a retrospective observational cohort study of hospital admissions cases aged < 18 years with injury-related ICD-10 codes using the German hospital database (GHD) was conducted. The maximum abbreviated injury scale and injury severity score were calculated using the ICD-AIS map provided by the Association for the Advancement of Automotive Medicine, adjusted to the German modification of the ICD-10 classification. The survival risk ratio was used to calculate the single worst ICD-derived injury (single ICISS) and a multiplicative injury severity score (multiplicative ICISS). Logistic regressions were conducted for each of the four above mentioned scores (predictors) to predict in-hospital mortality(outcome), in the selected trauma population and within four clinically relevant subgroups, using discrimination and calibration.

Results: 1,720,802 were trauma patients and ICD-AIS mapping was possible in 1,328,377 cases. Cases with mapping failure (n = 392,425;22.8%) were younger and had a higher mortality rate were excluded from the performance analysis. ICISS-derived scores had a better discrimination and calibration than ICD-AIS based scores in the overall cohort and all four subgroups (AUC ranges between 0.985-0.998 vs 0.886- 0.972 respectively).

Conclusion: Empirically derived measures of injury severity were superior to ICD-AIS mapped scores in the GHD to predict mortality in pediatric trauma patients. Given the high percentage of mapping failure and high mortality among cases with single coded injury, the single ICISS may be the most suitable measure of injury severity in this group of patients.