Clinical reasoning refers the process of creating a diagnosis and plan of treatment for a patient. To be an effective doctor you must be able to effectively carry out clinical reasoning, as errors in misdiagnosis can lead to unnecessary complications.

Clinical reasoning involves gathering information from the patient’s history, physical exam and test results to form a differential diagnosis. The differential diagnosis can include many possibilities as to what could be wrong with the patient. The end goal is to narrow down the differential to a diagnosis with a very high likelihood. Experienced physicians often generate their differentials more effectively than novices (such as early medical students) because increased case exposure and advanced heuristics and pattern recognition skills provide important clues. Further, these experts have more practice at the process of clinical reasoning and can generally more readily draw conclusions.

Give a stab at clinical reasoning with the case vignette below. As you obtain more information, try to determine what is going on with the patient.

So You Want to Be a Doctor

The key initial diagnostic features that make mononucleosis, an infection by the Epstein-Barr virus, the likely culprit given the history and physical exam results include the enlarged spleen, lymph nodes and tonsils, lesions on the soft palate, and fever. Subsequent blood tests showing elevated and atypical lymphocytes strengthen this reasoning. The fact that the patient has a sore throat, fatigue and is within the age range where mono often presents, also support the diagnosis. For this patient, it will be bed rest, fluids, Tylenol and throat sprays as needed until he regains his energy as his immune system fights off the virus.

Going through the process of clinical reasoning is the bread and butter of being a physician. This was a relatively straightforward case; patients with more complicated presentations may require more advanced reasoning skills. As a pre-medical student you can prepare for clinical reasoning in medicine by developing your own critical thinking skills by working through complex problems and scenarios in coursework and outside activities. Also, you can check out the clinical problem-solving cases on the New England Journal of Medicine website to get a taste of what it is like to work through challenging cases.


Ebell, M.H. 2004. Epstein-Barr Virus Infectious Mononucleosis. American Family Physician, 70(7), 1279-1287.

New England Journal of Medicine Clinical Problem-Solving

Tracie Addy is the Assessment Program Manager at the Yale University School of Medicine Teaching Learning Center and has a decade of experience teaching science to pre-med students. At the Teaching and Learning Center she manages programs related to student, program and educator assessment as well as the standardized patient program. She has a special interest in the development of clinical reasoning skills.