Research in cognition has yielded considerable understanding of the diagnostic reasoning process and its evolution during clinical training. This study sought to determine whether or not this literature could be used to improve the assessment of trainees’ diagnostic skill by manipulating testing conditions that encourage different modes of reasoning.
The authors developed an online, vignette-based instrument with two sets of testing instructions. The “first impression” condition encouraged non-analytic responses while the “directed search” condition prompted structured analytic responses. Subjects encountered six cases under the first impression condition, then six cases under the directed search condition. Each condition had three straightforward (simple), and three ambiguous (complex) cases. Subjects were stratified by clinical experience: novice (third and fourth year medical students), intermediate (post graduate year [PGY] 1 and 2 residents), and experienced (PGY 3 residents and faculty). Two investigators scored the exams independently. Mean diagnostic accuracies were calculated for each group. Differences in diagnostic accuracy and reliability of the examination as a function of the predictor variables were assessed.
The exam was completed by 115 subjects. Diagnostic accuracy was significantly associated with the independent variables of case complexity, clinical experience, and testing condition. Overall, mean diagnostic accuracy and the extent to which the test consistently discriminated between subjects (i.e., yielded reliable scores) was higher when participants were given directed search instructions than when they were given first impression instructions. In addition, the pattern of reliability was found to depend on experience: simple cases offered the best reliability for discriminating between novices, complex cases offered the best reliability for discriminating between intermediate residents, and neither type of case discriminated well between experienced practitioners.
These results yield concrete guidance regarding test construction for the purpose of diagnostic skill assessment. The instruction strategy and complexity of cases selected should depend on the experience level and breadth of experience of the subjects one is attempting to assess.