The diagnostic process

• Within minutes of beginning a clinical assessment a hypothesis is generated
• This may be based on common conditions in the epidemiological group or by 'pattern recognition' of pathognomonic features
• But the search is only just the beginning.......For the rest of the assessment further information is actively sought to confirm or exclude it, new information comes to hand and more possibilities are conjectured.  (see History Taking)

So what happens in a clinician's mind?

• Firstly an attempt at an unbiased, non leading and chronological account of the patient's symptom's is obtained.   (see Chronology suggests the pathology)
• Strategic open questions allow the patient to reveal more information without influencing the narrative e.g. 'and what happened next', 'did you notice anything else at the time of these symptoms', 'anything you noticed about when they would begin'.  (see the Art of history taking)
• Intermittently more specific questions are asked that help test the hypothesis. 'was it worse with exertion', 'did it radiate to the neck or jaw'
• Find a plausible cause for the the speculated condition.  e.g. 'do you have a history of high blood sugar....diabetes... high blood pressure....high cholesterol...'  (see Pathology)
• Reconsider and re-test hypotheses (per above) if there is contradicting or surprising information. (see Beware the Eureka syndrome)
• Re-rank the possibilities as more information is gathered.
• Begin examining the patient actively searching for signs consistent with your hypothesis.
• Actively look for complications of the proposed conditions e.g. myocardial infarction/heart failure, peptic ulcer/anaemia, COAD/respiratory failure. diabetes/neuropathy. ( see Assessing Severity)
  Choose the most discriminative tests e.g. high or low predictive values than can either confirm or exclude the possibilities.
• Re-rank the hypothesis again depending if the results are confirmatory OR exclusionary.
• Consider a therapeutic trial to test the hypothesis. (see Understanding management decisions)
• If the response is absent or delayed then reconsider the diagnosis or consider an added complication. e.g. unstable angina now becoming acute infarction