Purpose: Diagnostic errors have been attributed to faulty reasoning and cognitive biases, but minimizing errors requires understanding the mechanisms underlying biases. The authors investigated whether salient distracting features (SDFs)—case findings that tend to grab physicians’ attention because they are strongly associated with a particular disease, but are indeed unrelated to the problem—misdirect diagnostic reasoning, causing errors.
Method: In a 2012 study conducted at Erasmus Medical Centre, Rotterdam, 72 internal medicine residents diagnosed 12 clinical cases (6 simple, 6 complex) in three different formats: without a SDF, with a SDF in the beginning, and with a SDF at the end. In a within-subjects design, each participant solved 2 simple cases and 2 complex cases in each format. Proportions of correct diagnoses in each case type were compared by performing repeated-measures analysis of variance (ANOVA).
Results: There was a significant main effect of SDFs and a significant interaction effect between SDFs and case complexity. The presence of SDFs in the beginning of complex cases caused errors decreasing the proportion of correct diagnoses in comparison both with cases without SDFs (0.18, 95% CI, 0.13–0.23 versus 0.43, 95% CI, 0.35–0.51; P < .001) or with SDFs at the end (0.18, 95% CI, 0.13–0.23 versus 0.36, 95% CI, 0.29–0.43; P < .001). SDFs did not affect performance when presented near the end of cases.
Conclusions: SDFs early in a case are apparently an important source of diagnostic errors. Physicians should be aware of the need to overcome their influence.