Validation of the International Classification of Diseases 10th Edition-based Injury Severity Score (ICISS)

To compare the predictive power of International Classification of Diseases 10th Edition (ICD-10)-based International Classification of Diseases 9th Edition-based Injury Severity Score (ICISS) with Trauma and Injury Severity Score (TRISS) and ICD-9CM-based ICISS in the injury severity measure.

ICD-10 version of survival risk ratios was derived from 47,750 trauma patients from 35 emergency centers for 1 year. The predictive power of TRISS, the ICD-9CM-based ICISS and ICD-10-based ICISS were compared in a group of 367 severely injured patients admitted to two university hospitals. The predictive power was compared by using the measures of discrimination (disparity, sensitivity, specificity, misclassification rates, and receiver operating characteristic curve analysis) and calibration (Hosmer-Lemeshow goodness-of-fit statistics), all calculated by logistic regression procedure.

ICD-10-based ICISS showed a lower performance than TRISS and ICD-9CM-based ICISS. When age and Revised Trauma Score were incorporated into the survival probability model, however, ICD-10-based ICISS full model showed a similar predictive power compared with TRISS and ICD-9CM-based ICISS full model. ICD-10-based ICISS had some disadvantages in predicting outcomes among patients with intracranial injuries. However, such weakness was largely compensated by incorporating age and Revised Trauma Score in the model.

The ICISS methodology can be extended to ICD-10 horizon as a standard injury severity measure in the place of TRISS, especially when age and Revised Trauma Score were incorporated in the model. For patients with intracranial injuries, the predictive power of ICD-10-based ICISS was relatively low because of differences in the classifying system between ICD-10 and ICD-9CM.