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Risk stratification simplified: the worst injury predicts mortality for the injured children
Joseph J Tepas1, Cynthia L Leaphart, Brian G Celso
1Division of Pediatric Surgery, University of Florida College of Medicine-Jacksonville, Jacksonville, Florida 32209, USA. jjt@jax.ufl.edu
Insights
The International Classification Injury Severity Score (ICISS) accurately predicts pediatric survival. A child's most severe injury alone is a major driver of outcome, simplifying survival prediction.
Area of Science:
- Trauma research
- Pediatric critical care
- Injury epidemiology
Background:
- The International Classification Injury Severity Score (ICISS) traditionally uses the three most severe injuries to predict survival probability (Ps).
- Survival risk ratios (SRRs) are calculated from diagnosis-specific fatality proportions in a benchmark population.
- Pediatric-specific SRRs were developed using data from the National Pediatric Trauma Registry.
Purpose of the Study:
- To validate the ICISS as a predictor of pediatric injury survival.
- To determine if the single most severe injury (lowest SRR) is sufficient for predicting pediatric survival.
- To assess the contribution of the most severe injury to the overall predictive power of the ICISS.
Main Methods:
- Receiver operator characteristic (ROC) analysis was employed to evaluate predictive validity.
- A training set of 53,235 pediatric trauma patients (phase II) was used to derive SRRs.
- A test set of 50,199 pediatric trauma patients (phase III) was used to compare the predictive accuracy of the traditional ICISS with a model using only the lowest SRR.
Main Results:
- The area under the ROC curve for the traditional ICISS (0.935) was not significantly different from that using only the lowest SRR (0.932).
- The lowest SRR alone accounted for a substantial proportion (Nagelkerke pseudo R2 = 0.455) of the predictive power compared to the traditional three-diagnosis score (0.462).
- The dominance of the single worst injury was attributed to the frequency of coexistent non-fatal injuries rather than severity differences.
Conclusions:
- The ICISS is validated as a predictor of survival in pediatric injury.
- The most severe injury is the primary determinant of survival probability in pediatric trauma.
- These findings support using the single worst injury for targeted injury prevention and best practice analysis in pediatric trauma care.
Background:
The International Classification Injury Severity Score (ICISS) uses anatomic injury diagnoses to predict probability of survival (Ps) computed as the product of the survival risk ratios (SRR) of the three most severe injuries. SRRs are derived as the proportion of fatalities for every International Classification of Diseases-9th Revision-Clinical Modification diagnosis in a "benchmark" population. Pediatric-specific SRRs were computed from 103,434 entries in the National Pediatric Trauma Registry. We hypothesized that ICISS was a valid pediatric outcome predictor, and that the child's most severe injury; i.e., the lowest SRR, is the major driver of outcome, which can be used alone to predict survival.
Methods:
Receiver operator characteristic analysis was used to assess the predictive validity of ICISS. SRRs derived from 53,235 phase II patients were used as the training set to calculate the Ps for 50,199 phase III children comprising the test set. The survival probability (Ps) computed from the standard three diagnoses was compared with that computed from only the worst injury (lowest SRR). Records with a single diagnosis or Ps of 1, indicating no mortality potential, were excluded from the analysis. Nagelkerke pseudo R2 defined what proportion of the predicted Ps was the effect of the worst injury alone versus the traditional Ps.
Results:
A total of 25,239 records with at least two diagnoses with SRRs indicating risk of mortality were analyzed. The area under the receiver operator characteristic curve for traditional Ps was 0.935, compared with 0.932 for that calculated using only the lowest SRR. The difference of 0.003 was not significant (z = 1.061, p = 0.2888, NS). Nagelkerke pseudo R2 for the lowest SRR was 0.455 compared with 0.462 for the traditional three diagnosis Ps, which shows that the majority of Ps predictive power is related to the single injury with the lowest SRR. Further analysis demonstrated that this effect was related to frequency of coexistent injuries with no mortality risk rather than definable difference in severity.
Conclusion:
These data validate ICISS as predictive of pediatric injury survival. The dominant effect of the worst injury reflects an epidemiologic characteristic of pediatric trauma that will identify specific injuries for best practice analysis and focused injury prevention.
