International Classification of Diseases-based ISS - (ICISS)

Anatomical injury score based on the ICD-9 codes.

Uses survival risk ratios (SRRs) calculated for each ICD-9 discharge diagnosis. SRRs are derived by dividing the number of survivors in each ICD-9 code by the total number of patients with the same ICD-9 code. The ICISS is calculated as the simple product of the SRRs for each of the patient's injuries.

The ICISS has some advantages over the ISS.

• Allows for all injuries in predictions
• Injuries are more accurately modelled
• It uses information about all the injuries, together with the patient's three worst injuries
• The ISS, by contrast, is constrained to use only the single worst injury in the three most severely injured body regions.
• The use of measured rather than assigned values for injury severity by ICISS also contributes to improved accuracy of prediction.

ICD-9 codes are readily available and their use does not require special training or expertise. Moreover, the ICISS has the potential to account better for the effects of comorbidity on outcome by including the SRR for each comorbidity present.

The ICISS is more useful than the ISS in predicting other outcomes of interest (e.g. hospital length of stay, hospital charges, resource utilisation). Despite the apparent advantages of the ICISS, it has not yet replaced other methods of outcome analysis.

Limitations:

• ICD-9 code use varies from hospital to hospital
• ICISS  ignores physiological data
• Computational software is needed for calcualtions and predictions
• The claimed improvement of ICISS over ISS is not unique, as ASCOT and AP methods have produced similar results, and thus the ICISS is not conclusively a superior method.

Predicting outcome after multiple trauma: which scoring system?; Injury, Volume 35, Issue 4, April 2004, Pages 347-358; M. N. Chawda , F. Hildebrand , H. C. Pape and P. V. Giannoudis

Last updated 11/09/2015