Diagnostic Hypothesis Generation Cognitive scientists studying the thought processes of expert clinicians have observed that clinicians group data into packets, or "chunks," which are stored in their memories and manipulated to generate diagnostic hypotheses. Because short-term memory can typically hold only 7–10 items at a time, the number of packets that can be actively integrated into hypothesis-generating activities is similarly limited. The cognitive shortcuts discussed above play a key role in the generation of diagnostic hypotheses, many of which are discarded as rapidly as they are formed. A diagnostic hypothesis sets a context for diagnostic steps to follow and provides. | Chapter 003. Decision-Making in Clinical Medicine Part 3 Diagnostic Hypothesis Generation Cognitive scientists studying the thought processes of expert clinicians have observed that clinicians group data into packets or chunks which are stored in their memories and manipulated to generate diagnostic hypotheses. Because short-term memory can typically hold only 7-10 items at a time the number of packets that can be actively integrated into hypothesis-generating activities is similarly limited. The cognitive shortcuts discussed above play a key role in the generation of diagnostic hypotheses many of which are discarded as rapidly as they are formed. A diagnostic hypothesis sets a context for diagnostic steps to follow and provides testable predictions. For example if the enlarged and quite tender liver felt on physical examination is due to acute hepatitis the hypothesis certain specific liver function tests should be markedly elevated the prediction . If the tests come back normal the hypothesis may need to be discarded or substantially modified. One of the factors that make teaching diagnostic reasoning difficult is that expert clinicians do not follow a fixed pattern in patient examinations. From the outset they are generating refining and discarding diagnostic hypotheses. The questions they ask in the history are driven by the hypotheses they are working with at the moment. Even the physical examination is driven by specific questions rather than a preordained checklist. While the student is palpating the abdomen of the alcoholic patient waiting for a finding to strike him the expert clinician is on a focused search mission. Is the spleen enlarged How big is the liver Is it tender Are there any palpable masses or nodules Each question focuses the attention of the examiner to the exclusion of all other inputs until answered allowing the examiner to move on to the next specific question. Negative findings are often as important as positive ones in establishing and
