CAISS Injury Severity Scoring 5 — Questions and Answers
Question 1: Which statement about the Organ Injury Scale (OIS) and AIS is correct?
- OIS replaces AIS for all trauma scoring
- OIS grades (I–V) generally correspond to AIS severity levels for specific organs (Correct answer)
- OIS is used only for pediatric patients
- OIS scores are directly summed to compute ISS
Correct answer: OIS grades (I–V) generally correspond to AIS severity levels for specific organs
The AAST Organ Injury Scale grades (I–V) broadly parallel AIS severity codes and are often cross-referenced in operative trauma.
Question 2: A trauma patient has an ISS of 25. What is the approximate 30-day mortality rate in a typical US Level I trauma center?
- Less than 5%
- Approximately 10–20% (Correct answer)
- Greater than 50%
- Exactly 25%
Correct answer: Approximately 10–20%
An ISS of 25 corresponds to roughly 10–20% mortality depending on age, mechanism, and center performance.
Question 3: Which component is NOT part of the Revised Trauma Score (RTS)?
- Glasgow Coma Scale
- Systolic blood pressure
- Respiratory rate
- Injury Severity Score (Correct answer)
Correct answer: Injury Severity Score
The RTS uses only GCS, systolic blood pressure, and respiratory rate; ISS is an anatomic score not included in RTS.
Question 4: When coding a closed head injury, the AIS body region assigned is:
- Face
- External
- Head/Neck (Correct answer)
- Abdomen
Correct answer: Head/Neck
All brain and spinal cord injuries, skull fractures, and cervical injuries are coded under the Head/Neck region.
Question 5: For quality improvement benchmarking, W-statistics derived from TRISS represent:
- The worst-case ISS in a cohort
- The number of unexpected deaths per 100 patients (Correct answer)
- The weighted average AIS across all body regions
- The ratio of penetrating to blunt injuries
Correct answer: The number of unexpected deaths per 100 patients
The W-statistic estimates the number of survivors or non-survivors per 100 patients beyond what TRISS-predicted probability would expect.
Question 6: An AIS severity of 4 is described as:
- Serious
- Severe (Correct answer)
- Critical
- Fatal
Correct answer: Severe
AIS 4 is designated 'severe' on the six-point scale: minor(1), moderate(2), serious(3), severe(4), critical(5), unsurvivable(6).
Question 7: Which factor most directly determines why ISS is squared rather than simply summed?
- To produce a value between 0 and 100
- To weight more severe individual injuries more heavily in the aggregate score (Correct answer)
- To eliminate the influence of minor injuries
- To standardize scores across different AIS editions
Correct answer: To weight more severe individual injuries more heavily in the aggregate score
Squaring AIS values exponentially increases the contribution of higher-severity injuries, reflecting their disproportionate effect on mortality.
CAISS Injury Severity Scoring 5
Which statement about the Organ Injury Scale (OIS) and AIS is correct?