As an emergency medical technician (EMT), you often need to tell the difference between one medical condition and another, known as the differential process or differentiating the medical complaint. This can be a challenge when the presenting signs and symptoms are very similar.

Here's an example: A 54-year-old male presents with breathing difficulty and says his chest feels "tight." In this brief scenario, conditions that can cause that presentation include diseases such as asthma, chronic obstructive pulmonary disease (COPD), pulmonary embolus, and a heart attack, just to name a few. To narrow down the field of possible causes to a few probable ones, you have to play the medical detective — pulling information together through your assessment and coming to some conclusions based on your findings. You gather this information through two general approaches:

  • Asking patients about what's happening is called history taking. You want to know what's happening right now, known as the history of the present illness (HPI). A mnemonic, OPQRST, begins a line of questions that describes the circumstances of the patient's complaint. (OPQRST stands for Onset, Provocation/Palliation, Quality, Related/Radiation, Severity, and Time.) Then, you record information about the patient's past medical history (PMH). Another mnemonic, AMPL, provides background information that may be related to the patient's HPI. (AMPL stands for Allergies, Medications, Past medical history, and Last oral intake.)

  • Your attention is also focused on the physical examination. This is a hands-on evaluation of parts of the patient's body, feeling for bumps, masses, tenderness, and other physical findings. What specific findings you look for depends on what the complaint is. In the previous example of shortness of breath, you want to know what the patient's lung sounds are, whether there is any accessory muscle use, in what body position the patient presents, whether the patient's feet appear to be swelling, and whether the patient has a medical alert bracelet that indicates a medical problem.

    You also obtain a set of vital signs — the patient's blood pressure, pulse and respiratory rate, and skin signs. This information provides baseline knowledge on how well the body is maintaining itself while having a problem.

You combine your findings from the history taking and physical examination into one pile. As you piece it all together, consider which medical conditions can cause the greatest number of the findings that you uncovered during your assessment. The more a particular condition fits, the higher the likelihood that it is the cause.