How to Create Great Differential Diagnoses: An Introduction
If you have been following my blog, you appreciate the importance of diagnostic reasoning, but how do we actually apply these principles to practice? Coming up with the right diagnosis is a non-linear, fluid, and at times challenging process. The core skill that will improve your diagnostic reasoning is generating high quality differential diagnoses – let’s dive deep into generating focused yet comprehensive differential diagnoses.
What is a differential diagnosis? Simply put, it is a list of possible diseases that may account for a patient’s presentation. Putting together a differential is complex – it takes knowledge, experience, reflection, and refining. So how do we generate a differential diagnosis in practice? By utilizing diagnostic frameworks.
Case: Let’s say you are seeing a 20-year-old female with acute onset of left lower quadrant pain. You naturally ask yourself what could be the cause – is it ectopic pregnancy, ovarian torsion, or dysmenorrhea? But how do you ensure that you haven’t missed important considerations?
There are various frameworks one can use to generate differential diagnoses – common ones include the anatomic framework, systems framework, mechanisms framework, and the checklist framework. Often, multiple frameworks are needed for a single presenting complaint. Determining what framework to apply to a specific presenting complaint is a combination of preference and trial and error. For a female with left lower quadrant pain, an anatomic approach works well – what anatomic structures could be the source of her pain?
Anatomic approach to left lower quadrant pain (female) - *this is not a comprehensive list.
The anatomic framework helps organize your differential diagnosis of left lower quadrant pain. It helps guide your history and physical to rule in and rule out sources of left lower quadrant pain on your list.
In this case, your patient says she was lifting heavy weights and felt a bulge in her groin which was when her pain started. She is not sexually active, has had recent negative STI testing, and is not having any changes to her bowel or bladder function. Her history leads you to think that most likely this is a musculoskeletal issue, or perhaps a hernia. Although this still doesn’t tell you what to do next (that will depend on your pre-test probability), it has helped make sure you have thought about all possible causes of her symptoms.
Key Take Home Points
Challenge yourself: Use a diagnostic framework (or a combination of frameworks) to organize your thinking and differential diagnosis around a presenting health complaint - this will help you think through all the major possibilities.
Stay tuned for the 4-part series on diagnostic frameworks where we will review the anatomy, systems, mechanisms, and checklist frameworks.
References/Readings
1. Schmidt HG, Boshuizen HPA. On Acquiring Expertise in Medicine. Educational psychology review. 1993;5(3):205-21.