Assessment: Health History, Physical Examination, and Diagnostic Reasoning
What is really being tested
Assessment items almost always ask for the next best step, not the final answer. Know the architecture of the encounter: chief complaint, HPI in OLDCARTS format (onset, location, duration, character, aggravating/associated, relieving, timing, severity), past medical/surgical, medications with adherence, allergies with reaction type, family and social history including occupational exposures, and a targeted review of systems. A comprehensive history is for new patients and undifferentiated problems; a focused history is for follow-up of a known problem.
Examination fluency
Expect technique-level questions. Blood pressure requires a correctly sized cuff, seated rest, arm at heart level, and averaging two readings. Use the bell for low-pitched sounds (S3, S4, mitral stenosis) and the diaphragm for high-pitched (aortic regurgitation, rubs). Know provocative maneuvers and their limits: Murphy for cholecystitis, straight-leg raise for radiculopathy, Phalen/Tinel for carpal tunnel, Ottawa rules to decide on imaging.
Reasoning with numbers
Treat every test as a revision of probability. Sensitivity rules out (SnNout); specificity rules in (SpPin); likelihood ratios move you from pretest to posttest odds. Positive predictive value falls when prevalence is low, so a positive result in a low-risk patient is often a false positive.
Traps
- Equating a positive test with a diagnosis.
- Ordering imaging before examining or assigning pretest probability.
- Missing atypical presentations: MI without chest pain in women and older adults; delirium or a fall as the only sign of infection in elders.
- Applying adult norms to children or pregnancy (higher resting heart rate, lower blood pressure).
Worked rule of thumb
A patient with a Wells score of 4 for pulmonary embolism has about 17% pretest probability. A D-dimer with 95% sensitivity and 40% specificity gives a negative likelihood ratio near 0.13 and a positive near 1.6. A negative result drops probability to roughly 3% - stop testing. A positive result reaches only about 25% - proceed to imaging, and do not start anticoagulation on the D-dimer alone.