What Is An Injury Severity Score?

“The Injury Severity Score (ISS) is an established medical score to assess trauma severity. It correlates with mortality, morbidity and hospitalization time after trauma. It is used to define the term major trauma. A major trauma (or polytrauma) is defined as the Injury Severity Score being greater than 15. Wikipedia”
TBI Clinic Can Treat Frontal Injuries

 The Injury Severity Scale is a metric that helps to describe the score of the severity of an injury. The Injury Severity Score (ISS) is a measure of the injury severity (i.e. the degree to which an injury affects a person’s health). The ISS is based on five factors:

The ISS has main components:

  1. Time
  2. Location
  3. Type of Injury
  4. Level of Acuity, and 
  5. Severity of Injury  

  How to Interpret the Injury Severity Score?

The Injury Severity Score (ISS) is a widely used and highly accurate measure of the severity of an injury. The ISS score is based on the following four key injury criteria:

  1. Brace/Tourniquet reduction: This score is determined by measuring the time from when the compressions are applied to when the patient awakens from bracing. A score of 1 indicates a time of <5 min; 2=5-10 min; 3=10-15 min; and 4= >15 min.
  2. Time to Resuscitation: A score of 1 indicates that it takes less than 10 minutes for the patient to be resuscitated, 2=10-15 minutes, 3=20-30 minutes, & 4= >30 minutes.
  3. Time to Airway Access: A score of 1 indicates that it takes less than 10 minutes for the patient to have access to a suction device or airway, 2=10-15 minutes, 3=20-30 minutes, & 4= >30 minutes.
  4. Pain Severity Score: A score of 1 means there is no pain at all and can be increased up to 5 if the patient has suffered some degree of pain during or after their injury (e.g., severe headache).

While these four types of injury are considered by many as the four most common in hospitalized patients, the Injury Severity Score has been found useful in assessing other injuries as well including neck injuries in conjunction with the Glasgow Coma Scale (GCS) and total body injuries compared with bodyweight alone (i.e., Body Mass Index BMI). 

As such many hospitals have developed their own ISS scores which can be found on our website.  A number of studies have also shown that ISS scores correlate well with both physical findings such as neurologic deficits and upper/lower extremity radiographs.  

The value in using ISS scores for identifying differences between groups was recently demonstrated in a study that compared ISS scores between pediatric patients who underwent spinal fusion surgery versus those who did not. 

The study showed significant differences in postoperative pain scores between both groups but there was no difference in ISS scores between them at 6 months follow up.  In addition, there was also no difference between groups at 12 months follow-up either — though it should be noted that this study was conducted on pediatric patients only so it’s possible they had different outcomes or were more severely injured than those studied here specifically. Overall, this seems like

  What are the different categories of the injury severity score?

A wide range of instruments exists to rate the severity of a particular injury. For example, the American College of Emergency Physicians has a score for a head injury, which ranges from 1 (no symptoms) to 25 (death). 

Some investigators have found that the ISS can be used to predict mortality following brain trauma by identifying patients who are at risk for death and those who are not.

“Another common measure is the Glasgow Coma Scale (GCS). The GCS is a continuous scale that ranges from 0-15 where 0 is normal and 15 is severe.”

 A higher score indicates more severe brain damage, but it doesn’t necessarily mean more serious illness.

The Associated Injury Score (AIS) is an instrument that rates how seriously someone was injured. On this scale, injuries range from 1 (not at all serious) to 10 (very serious), with 0 being minimal and 10 being fatal. Some organizations use an average score on the scale (e.g., 3), while others use each item as a range of scores within which they consider an injury “serious enough” to be considered “fatal” rather than merely “mild” or “moderate” injuries. In other words, any score above 5 is considered fatal.

The Barrell Injury Matrix Score provides a quantitative assessment of how severe an injury was in a given situation; it ranges from 0-4 with 0 being no injury and 4 being death or substantial disability or loss of life expectancy. A higher score indicates more severe brain damage, but it doesn’t necessarily mean more serious illness or death.

The Injury Severity Score chart usually contains several grades on all four scales: for most people, these grades correspond to 1-4 grade numbers on company charts or hospital charts/radiographs: Grade I=1 slight, 1 moderate, and 2-3 mild; Grade II=2 mild; Grade III=3 moderate; Grade IV=4 major with Grade I-IV gradations corresponding to degrees of severity within those grades as follows: Grade I = no injury; Grade II = slight; Grade III = moderate; Grade IV = major with grade I-IV gradations corresponding to degrees of severity within those grades as follows: Grade I = no injury [0-1]; Grade II = mild [2-3]; Grade III = moderate [4-.5];Grade IV=major [6-.9].

When using the ISS in an emergency room

How to Interpret the Glasgow Coma Scale?

The Glasgow Coma Scale (GCS) is the most commonly used and widely accepted tool for assessing the severity of unconsciousness in emergency situations. The GCS is a simple and reliable scale that provides an estimate of the severity of unconsciousness or absence of consciousness in adults.

The scale uses a set of simple questions:

  1. Is your person unresponsive?
  2. Does your person have any abnormal movements?
  3. Does your person appear to be awake?
  4. Are there any signs or symptoms indicating recovery?
  5. Is your person sensitive to light and sound?

  What are the different categories of the Glasgow Coma Scale?

If you are a new player in the healthcare space, the Glasgow Coma Scale is probably the most well-known form of measurement for both people who are a victim of a serious injury and for health care professionals.

A study published in the Journal of Neurology, Neurosurgery & Psychiatry found that patients with brain injuries have a different Glasgow Coma Score than healthy volunteers. The scores used to determine injury severity also differ between healthy volunteers and brain-injured patients.

This suggests that there is a difference between healthy volunteers and brain-injured patients, which may be due to different mechanisms of injury.

It’s actually pretty obvious that if you are injured, you should have something to measure your injury severity score (ISS). However, it’s not very common to figure out how to calculate this score until after the fact (if at all). Fortunately, though, there are many resources available online which can help you do so.

Below are links to several resources on how to calculate ISS:




Special mention: Keep in mind that the GCS is not completely standardized between studies — this means things vary quite drastically by study (e.g., while one study found no effect on cognitive function or memory among brain-injured patients using different instruments, another found evidence of immediate improvement in memory tests with less severe injuries). 


This means some measurements will be more sensitive than others and some will be more specific than others; some tests may not be sensitive enough for use as an ISS measure (e.g., cognitive testing); and some instruments may not accurately reflect the degree of unconsciousness or amnesia (e.g., CT scans do not accurately count gross body movements). 

For these reasons, we recommend trying each method as they apply with one another (i.e., repeat this calculator if needed) before basing your decision upon one particular marker (such as GCS or ISS) as it indicates differences among studies — it may be best to use several methods at once; however, if you

 Brain Injury and Injury Severity Score

A few years ago, the first brain injury laws were passed. And while the majority of these are very helpful in raising awareness, there is still a large population of people who have suffered a brain injury but aren’t aware and don’t need to be. 

That’s because they are unaware of the severity of their condition and/or it doesn’t register as a major concern until something more serious happens.

To address this, here is an injury severity score calculator that you can use to quickly find out what the severity of your brain injury is. 

The tool tries to take into account your age, gender, and where you were injured. It also takes other factors (such as your level of education) into consideration. You can review the result here: http://www.braininjuryassessment-assessment-tool.com/braininjuryeverlasting-illness/.

 What are Some Other Injury Score Methods?

The Injury Severity Score (ISS) is a tool that can be used to determine how severely a person was injured. It is calculated using several commonly used scales, including:

  • The Glasgow Coma Scale (GCS)
  • The Hematological Amnesia Scale (HAS)
  • The Acute Physiological Response to GVHD Scrambling Scale (APROGS)
  • The Barrell Injury Matrix Score  (BIMSS)

The APROGS and BIMSS are based on the American College of Surgeons Classification of Severity of Injuries. A patient who is 70% GCS, 10% HAM and 20% MBI on the Glasgow Coma Scale will have an APROGS score of 3 and a BIMSS score of 4.0. A patient who is 40% GCS, 20% HAM and 10% MBI on the Glasgow Coma Scale will have an APROGS score of 2.5 and a BIMSS score of 3.0.

What is the Barrell Injury Matrix Score

Injury Severity scores (ISS) are basically a measure of how severe a particular injury is. They can be used to help determine which injuries are more serious than others. For example, an ISS of 30 means that the injury is 30 times more severe than the other injuries in a given category. 

In other words, it is 30 times worse or as serious as an extreme instance of another injury.

What is considered “severe”? The Injury Severity Score (ISS) is a numeric score that measures the severity of an injury, usually broken down into three categories: 1-30 = Non-life threatening 2-30 = Life threatening 3-30 = Severe

Injury Severity Scores range from 1 to 75 and should be interpreted in isolation from other metrics used to determine severity of an injury. These scores do not necessarily indicate how severe the injury was (and may even indicate whether the injury was caused by a physical or chemical event). 

For example, if you injure your wrist when falling off a ladder and get ISS 3 for your wrist, this does not necessarily mean that your wrist was injured by falling off the ladder, but rather that you fell on your wrist by accident and sustained an accident-related injury. 

The major consideration with ISS scores is how severe the injury was (or could be) when it occurred. 



About The Author

Tiffany Dyar

Tiffany Dyar is the former Executive Director for The Center for Health Innovation & Implementation Science, and the former Program Manager at Regenstrief Institute.Tiffany has co-authored several medical publications including The American Journal of Critical Care  Journal of General Internal Medicine Trials Journal  Best Practices in Mental Health  & The New England Journal of Medicine

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