Clinical Reasoning and Differential Diagnosis
What the exam expects
Demonstrate hypothetico-deductive and pattern-recognition reasoning: generating hypotheses, weighting findings by sensitivity/specificity, and testing competing diagnoses. Understand red flags and yellow flags, screening for serious pathology (fracture, infection, malignancy, cauda equina, vascular), and when to refer. Know the difference between impairment-level and function-level reasoning and how to use clinical prediction rules appropriately (as aids, not substitutes for judgment).
Traps
Questions often reward recognizing when a presentation is inconsistent with a mechanical diagnosis-e.g., night pain unrelieved by position change, unexplained weight loss, fever, progressive neurologic deficit. A common trap is anchoring on an initial hypothesis and ignoring disconfirming data (confirmation bias). Another is over-applying a prediction rule outside its validation population. Distinguish "most likely" from "most dangerous" diagnoses.
Rule of thumb
When a red flag is present, rule out serious pathology before proceeding with mechanical treatment-safety precedes specificity.
Worked example
A patient with low back pain reports saddle anesthesia and new bladder incontinence. Despite otherwise mild symptoms, these are red flags for cauda equina syndrome requiring urgent referral, not a trial of exercise.