Should learners reason one step at a time? A randomised trial of two diagnostic scheme designs.
BACKGROUND
Making a diagnosis can be difficult for learners as they must integrate multiple clinical variables. Diagnostic schemes can help learners with this complex task. A diagnostic scheme is an algorithm that organises possible diagnoses by assigning signs or symptoms (e.g. systolic murmur) to groups of similar diagnoses (e.g. aortic stenosis and aortic sclerosis) and provides distinguishing features to help discriminate between similar diagnoses (e.g. carotid pulse). The current literature does not identify whether scheme layouts should guide learners to reason one step at a time in a terminally branching scheme or weigh multiple variables simultaneously in a hybrid scheme. We compared diagnostic accuracy, perceptual errors and cognitive load using two scheme layouts for cardiac auscultation.


METHODS
Focused on the task of identifying murmurs on Harvey, a cardiopulmonary simulator, 86 internal medicine residents used two scheme layouts. The terminally branching scheme organised the information into single variable decisions. The hybrid scheme combined single variable decisions with a chart integrating multiple distinguishing features. Using a crossover design, participants completed one set of murmurs (diastolic or systolic) with either the terminally branching or the hybrid scheme. The second set of murmurs was completed with the other scheme. A repeated measures manova was performed to compare diagnostic accuracy, perceptual errors and cognitive load between the scheme layouts.


RESULTS
There was a main effect of the scheme layout (Wilks' λ = 0.841, F3,80= 5.1, p = 0.003). Use of a terminally branching scheme was associated with increased diagnostic accuracy (65 versus 53%, p = 0.02), fewer perceptual errors (0.61 versus 0.98 errors, p = 0.001) and lower cognitive load (3.1 versus 3.5/7, p = 0.023).


CONCLUSIONS
The terminally branching scheme was associated with improved diagnostic accuracy, fewer perceptual errors and lower cognitive load, suggesting that terminally branching schemes are effective for improving diagnostic accuracy. These findings can inform the design of schemes and other clinical decision aids.
Department of Medicine, Division of Cardiology, Western University, London, Ontario, Canada.
Sarah
S
Blissett
Department of Medicine, Division of Endocrinology and Metabolism, Western University, London, Ontario, Canada.
Deric
D
Morrison
Department of Medicine, Division of Cardiology, Western University, London, Ontario, Canada.
David
D
McCarty
Department of Medicine, Division of Cardiology, McMaster University, Hamilton, Ontario, Canada.
Matthew
M
Sibbald
D001024:Aortic Valve Stenosis; D003198:Computer Simulation; D018592:Cross-Over Studies; D003657:Decision Making; D004521:Educational Measurement / Q000379:methods; D006326:Heart Auscultation; D006337:Heart Murmurs / Q000175:diagnosis*; D006349:Heart Valve Diseases; D006801:Humans; D007388:Internal Medicine / Q000193:education*; D007396:Internship and Residency