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    Injury Severity Score (ISS)

    Standardizes severity of traumatic injury based on worst injury of 6 body systems.
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    INSTRUCTIONS

    Rate only the most severe injury from each body system. Used primarily in research settings, so calculation of the ISS should not delay initial management of patients with traumatic injuries.

    When to Use
    Pearls/Pitfalls
    Why Use

    • The ISS is a score that attempts to standardize the severity of injuries sustained during a trauma.

    • This standardization allows one to more accurately study and predict morbidity and mortality outcomes after traumatic injuries.

    • Initially derived in patients with blunt traumatic injury from motor vehicle accidents only.

    • The ISS is not intended to be used for bedside decisions regarding a single patient in the emergency department setting, but rather as a tool to standardize the study of trauma patients.

    • Due to the nature of the score, multiple combinations of Abbreviated Injury Scale (AIS) scores may arrive at the same ISS, each of which may indicate a different mortality rate. For example, an ISS of 17 can be made from patients with a combination of points based on the three most severe injuries, such as (4, 1, 0) or (3, 2, 2). The ISS also gives equal importance to each body region.

    • Patients with an AIS of 6 in any body system are automatically assigned an ISS of 75, the maximum possible score.

    Due to the heterogeneous nature of trauma patients, standardizing severity of traumatic injury allows for much larger sample populations in trauma research studies.

    No injury
    Minor
    Moderate
    Serious
    Severe
    Critical
    Unsurvivable
    No injury
    Minor
    Moderate
    Serious
    Severe
    Critical
    Unsurvivable
    No injury
    Minor
    Moderate
    Serious
    Severe
    Critical
    Unsurvivable
    No injury
    Minor
    Moderate
    Serious
    Severe
    Critical
    Unsurvivable
    No injury
    Minor
    Moderate
    Serious
    Severe
    Critical
    Unsurvivable
    No injury
    Minor
    Moderate
    Serious
    Severe
    Critical
    Unsurvivable

    Result:

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    Next Steps
    Evidence
    Creator Insights

    Advice

    As the ISS is intended as more of a research tool, calculation of the ISS should not affect initial management of the patient with traumatic injuries.

    Management

    • In all trauma patients, initial treatment strategy should focus on the primary and secondary survey, and assessing and stabilizing the patient.
    • This score is intended mostly for research purposes but may have broader clinical use in the ICU for prognostication following initial stabilization of traumatic injuries.

    Formula

    Assign an Abbreviated Injury Scale (AIS) Score to the most severe injury in each body system as follows:

    Severity

    AIS

    No injury

    0

    Minor

    1

    Moderate

    2

    Serious

    3

    Severe

    4

    Critical

    5

    Unsurvivable

    6

    Then, if the 3 most severe injuries in 3 body systems are A, B, and C, then

    ISS = A² + B² + C²

    If a patient has an AIS of 6 in any body system, they are automatically assigned an ISS of 75.

    Evidence Appraisal

    • The ISS was derived by Baker et al (1974) by taking the previously used Abbreviated Injury Scale (AMA Committee on Medical Aspects of Automotive Safety 1971) and adding up the squares of each of the three most severe body systems, in an effort to add increasing weight to the most severe injuries.

    • The top three most severe injuries were used to calculate the final score because it was shown that injuries that alone would not necessarily be life threatening, had a significant effect on mortality when occurring in combination with other severe injuries.

    • The derivation study included only injuries sustained from motor vehicle collisions, including occupants of the vehicles as well as pedestrians involved.

    • Further validation studies have validated the study to include other mechanisms of injury.

    • A study of 875 patients with gunshot wounds by Beverland et al (1983) showed that an increasing ISS was associated with increasing mortality (chi-squared = 83.31, p <O.0Ol).

    • A study by Bull (1978) confirmed the correlation between increasing ISS and increasing mortality for road traffic accidents,  as well as increasing mean hospital length of stay with increasing ISS.

    • Semmlow and Cone (1976) found similar findings to Baker et al in terms of relationship between ISS and mortality when they looked at 8,852 trauma patients from the Illinois Trauma Program, including both vehicular and non-vehicular trauma. They also found ISS to correlate with hospital length of stay.

    Literature

    Dr. Susan Baker

    About the Creator

    Susan Baker, MPH, is an professor and epidemiologist specializing in injury prevention at Johns Hopkins Bloomberg School of Public Health and was the first director of the Center for Injury Research and Policy. She is well known for authoring the Injury Fact Book. Professor Baker's teaching and research is aimed at influencing policy changes that will reduce the likelihood of injury for thousands of people.

    To view Dr. Susan Baker's publications, visit PubMed

    Content Contributors
    • Max Berger, MD
    Reviewed By
    • Alexandra Ortego, MD
    About the Creator
    Dr. Susan Baker
    Content Contributors
    • Max Berger, MD
    Reviewed By
    • Alexandra Ortego, MD