Q&A: Is Undertriage Bad?

After my discourses on under- and over-triage in the last week, I received an interesting question from a reader: although undertriage seems bad from a theoretical standpoint, are there any objective negative consequences?

As you might imagine, there is little literature on this topic. The incidence is low, so it’s tough to design a study with enough power to come to any solid conclusions. There are two studies that I can cite that shed as much light on the subject as possible.

The first looks at system undertriage at the EMS level. A Canadian study looked at patients with severe injuries (identified by ISS>15 after admission) who were taken to trauma centers (correct triage) vs non-trauma centers (undertriage). After solid statistical analysis of over 11,000 patients, they found that mortality in the undertriage group was 24% higher than the correctly triaged patients.

A second study looked at undertriage in one trauma center (1,424 patients) using their standard triage criteria, not ISS. The undertriage group had a significantly lower ISS (17 vs 25). The correctly triaged patients were more frequently intubated in the ED, more likely to be admitted to the ICU, and had longer ICU and hospital stays. Mortality was not significantly different. The problem with this study is that most of the undertriage group probably did not need a trauma activation, based on their lower ISS. The higher ISS patients (who met triage criteria) needed an airway earlier and required critical care more often. These data show that the institution probably needs to adjust its triage criteria!

Bottom line: The Canadian study shows the danger of undertriage prior to reaching definitive care. There is no good literature that illustrates its danger once the patient is at a trauma center. But there is support for the converse idea that appropriately triaged patients get definitive management sooner (airway, critical care). Any takers for designing the study to answer this question?


  1. Survival of the fittest: the hidden cost of undertriage of major trauma. J Amer Col Surgeons, 211:804-811, Dec 2010.
  2. Outcome assessment of blunt trauma patients who are undertriaged. Surgery 148(2): 239-245, Aug 2010.

Undertriage Revisited

I’ve updated my original post on trauma undertriage when activating your trauma team. The initial post gave a general approach that was reasonably accurate as long as the number of missed activations was low. Here’s the new and improved version!

Trauma centers look at over- and undertriage rates as part of their performance improvement programs. Both are undesirable for a number of reasons. I’ll focus on undertriage today, why it happens and what can be done about it.

Undertriage in trauma care refers to the situation where a patient who meets criteria for a trauma activation does not get one. First, calculate your “magic number”, the number of patients who should have been trauma activations.

If you track the exact triage criteria met at your hospital, it is calculated as follows:

 Magic Number = (Number of ED trauma patients who met activation criteria
                                           but were not trauma activations)

If you don’t track the triage criteria, you can use ISS>15 as a surrogate to identify those patients who had severe enough injuries that should have triggered an activation. This is not as accurate, because you can’t know the ISS when the patient comes in, but it will do in a pinch. In that case, the magic number is:

Magic Number = (Number of ED trauma patients with ISS>15
                                           but were not trauma activations)

Your undertriage rate is then calculated as follows

                                        Magic Number
        ———————————————————–    x 100
           (Total number of trauma activations) + Magic Number

Undertriage is bad because patients who have serious injuries are not met by the full trauma team, and would benefit from the extra manpower and speed possible with an activation.

The most common causes for undertriage are:

  • Failure to apply activation criteria
  • Criteria are too numerous or confusing
  • Injuries or mechanism information is missed or underappreciated

Undertriage rates can range from 0% to infinity (if you never activate your trauma team). A general rule is to try to keep it below 5%.

If your overtriage rate is climbing past the 5% threshold, identify every patient who meets the ISS criterion and do a complete ED flow review as concurrently as possible. Look at their injuries/mechanism and your criteria. If the criteria are not on your activation list, consider adding them. If the criterion is there, then look at the process by which the activation gets called. Typically the ED physicians and nurses will be able to clarify the problem and help you get it solved.