Does The MPDS Over-Triage?

Does the Medical Priority Dispatch System^™ (MPDS^®) over-triage? To answer this question, we must look more closely at what the term “triage” really means.

In medicine, triage is a process that contains three distinct steps: evaluation, prioritization, and resource allocation. The MPDS accomplishes the first two steps in a very detailed and consistent manner by using a unified (the same everywhere) protocol system with a standardized question, instruction, and coding system, designed specifically for triage in the remote, completely non-visual environment of emergency medical dispatch centers.

The third step, resource allocation, is assigned entirely by the local or regional emergency medical services (EMS) agency that serves the specific area in which its patients are located. Therefore, one way to look at the MPDS evaluation and coding process is to see it as a way to assess patient risks and prioritize those risks in such a way that allows the local EMS agency to assign its resources accordingly and correctly—but without potentially dangerous under-response.

When viewing risk through the lens of the MPDS, it’s important to understand that patient risk is not the same as a confirmed outcome or diagnosis—or even a lasting condition. While the MPDS Priority Levels and Determinant Codes certainly have a strong association with patient acuity in the aggregate—i.e., the higher the priority of the code, the more likely the patient is to have a serious condition determined by the responding EMS crews and hospital diagnoses—they are designed, by necessity, to find any, and reasonably account for, all potentially serious patient conditions at the point of dispatch, so that a timely and sufficient EMS response, and their needed level of evaluation, can be assigned.

A good example of risk versus final outcome is how the MPDS assesses the level of consciousness in a conscious patient whose mentation (mental activity or Level of Consciousness) is impaired. Once the patient is determined to be “awake” by Case Entry Questioning, the “responding normally” question is often used to determine “alert” or “not alert.” An Emergency Medical Dispatcher’s (EMD) finding of “not alert” is not a confirmation that the patient will remain in that state for any length of time. This is one reason that responding paramedic crews sometimes arrive to find a patient now fully alert, even when the MPDS coding indicated a “not alert” patient.

This can lead to the incorrect assumption that the patient was “over-triaged” by the EMD because of the MPDS. However, the EMD’s finding of “not alert” at the time of their assessment is simply a patient “snapshot in time” of a condition that was, and may still be, present—and therefore suggests a certain degree of risk— regardless of what the patient’s ultimate outcome turns out to be. The responding paramedic would be well-served to note that the EMD very likely assessed the patient as “not alert” at the time of the emergency call, rather than simply dismiss it as an “over-triage error” when their patient findings (some time later) can always be different.

The good news is that the MPDS has a method to put the “not alert” finding at dispatch in its proper context when assigning a Determinant Code. In other words, not alert can carry a somewhat different risk depending on the patient context. For example, a Not Alert diabetic patient (13-C-2) is assigned a different level of risk (Determinant Level) than a Not Alert patient with a suspected head injury or other trauma (30-D-3). In the case of a diabetic, the CHARLIE-level coding suggests an intermediate risk, best handled as a face-to-face evaluation by an advanced life support (ALS) crew that can administer a sugar IV solution to a hypoglycemic patient that would help reverse that patient’s altered level of consciousness; the DELTA-level code suggests a more rapid response due to the risk of underlying severe head trauma that may require immediate ALS care and transport to a trauma center for quick scans and/or emergency surgery.

Another example is the chest-pain only patient in the cardiac age range (with no other cardiac symptoms). The MPDS Determinant Code for such a patient would be a 10-C-3 (Breathing normally [≥35]). This code reflects the patient’s need for an ALS assessment in a timely manner, which indeed is the standard of care and practice for all state-of-the-art EMS agencies. Note that this code does not mandate a lights-and-siren response; to the contrary, the MPDS generic response is a single ALS ambulance, COLD response (no lights-and-siren).

Now, consider another chest pain patient over age 35, but now with an additional cardiac symptom such as not alert, clammy, severe respiratory problems (difficulty speaking between breaths), changing color, or a history of heart attack or angina. In such cases, the chances of the patient having an acute myocardial infarction (AMI) are increased as compared to the previous example, hence one of the 10-D (higher priority DELTA-level) codes in the MPDS is assigned. In this case, the accepted practice is an immediate (lights-and-siren) response from an ALS crew. This is true regardless of whether or not the crew discovers an unstable heart rhythm after its assessment, suspects an AMI, provides a time-sensitive intervention, or transports the patient urgently or not.

Resource allocation—the third step in the triage process—involves assigning the appropriate response to the patient. This step is sometimes (incorrectly) attributed to the MPDS, when, in fact, it is entirely determined by the local or regional EMS agency authorities (and not ever the IAED!). Again, there’s good news here when using the MPDS: The MPDS contains approximately 900 Determinant Codes in Protocols 1–47, and when all the Determinant Code suffixes are included, that number balloons to nearly 3,300. This gives local and regional EMS authorities maximum flexibility in determining how to allocate scarce responder resources to get the most effective and efficient mix of timely response and responder capabilities.

One way an EMS agency can allocate its resources, more efficiently and effectively, is to expand the variety of response options in the system, i.e., develop new, more targeted, responder configurations beyond the traditional ambulance-only or first responder-with-an-ambulance options.

One of the most overlooked and underutilized processes to actively start with is the direct use of the MPDS standardized 6-level Response Matrix (ECHO, DELTA, CHARLIE, BRAVO, ALPHA, OMEGA), which is designed specifically for response-variable MPDS use to not over-triage, by getting the right number and type of resource(s) to the right conditions and/or situation in a clinically reasonable timeframe. This was actually the initial basis for the MPDS. A growing and apparently very safe practice is now sending all BRAVO-level code responders COLD whether Fire 1st responders or single or associated transport ambulance.

Comprehensive patient care is a process that requires a number of important, refined steps. In EMS, that starts with a well-trained, certified EMD (who is CDE-current), using a state-of-the-art, established protocol to assess and prioritize patient risk safely, consistently, and with as much detail as possible.

As the Doc says, “Like putting in golf, be advised that it’s occasionally okay to hit it past the hole (over-triage), but never under (short), because ‘short’ can never go in!”

Sources
1. Scott, G., Clawson, J., Olola, C., Miko, M., Schultz, B., Patterson, B. “Lumping disparate emergency dispatch priority levels together creates an assumption error regarding ‘overtriage.’” Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine. 2025; 33(117).

2. Nicoletta, V., Robitaille-Fortin, M., Bélanger, V., Mercier, E., Harrisson, J. “Performance measures of the medical priority dispatch system in an urban basic life support system.” Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine. 2025; 33(94).

3. Clawson, J.J., Gardett, I., Scott, G., Fivaz, C., Barron, T., Broadbent, M., Olola, C. “Hospital-Confirmed Acute Myocardial Infarction: Prehospital Identification Using the Medical Priority Dispatch System.” Prehospital and Disaster Medicine. 2017.

4. Gardett, I., Olola, C., Scott, G., Broadbent, M., Clawson, J. “Comparison of Emergency Medical Dispatcher Stroke Identification and Paramedic On-Scene Stroke Assessment.” Annals of Emergency Dispatch & Response. 2017; 5(1). 6-10.

5. Clawson, J., Barron, T., Scott, G., Siriwardena, A.N., Patterson, B., Olola, C. “Medical Priority Dispatch System Breathing Problems Protocol Key Question Combinations are Associated with Patient Acuity.” Prehospital and Disaster Medicine. 2012; 27(4). 1-6.

6. “Salt Lake City Fire Dept. Response Time Study on BRAVO-level Calls.” Pg. 11.33 (Fig. 11-21). Principles of Emergency Medical Dispatch. Sixth edition. International Academies of Emergency Dispatch; Salt Lake City.