On Some Statistical and Axiomatic Properties of the Injury Severity Score

TL;DR

This paper investigates the statistical and axiomatic properties of the Injury Severity Score (ISS), revealing potential biases and undesirable features arising from its design choices, which impact its effectiveness in patient triage.

Contribution

The study provides a formal analysis of ISS using decision science, uncovering its axiomatic and statistical limitations and biases.

Findings

ISS has unintended biases due to its quadratic aggregation method.

Certain design choices in ISS lead to undesirable properties affecting triage accuracy.

The paper highlights the need for revising or improving the scoring method.

Abstract

The Injury Severity Score (ISS) is a standard aggregate indicator of the overall severity of multiple injuries to the human body. This score is calculated by summing the squares of the three highest values of the Abbreviated Injury Scale (AIS) grades across six body regions of a trauma victim. Despite its widespread usage over the past four decades, little is known in the (mostly medical) literature on the subject about the axiomatic and statistical properties of this quadratic aggregation score. To bridge this gap, the present paper studies the ISS from the perspective of recent advances in decision science. We demonstrate some statistical and axiomatic properties of the ISS as a multicrtieria aggregation procedure. Our study highlights some unintended, undesirable properties that stem from arbitrary choices in its design and that call lead to bias in its use as a patient triage criterion.