Bayesʼ Theorem and the Physical Examination: Probability Assessment and Diagnostic Decision Making

Abstract

Purpose To determine how examination findings influence the probability assessment and diagnostic decision-making of third- and fourth-year medical students, internal medicine residents, and academic general internists. Method In a 2008 cross-sectional, Web-based survey, participants from three medical schools were asked questions about their training and eight examination scenarios representing four conditions. Participants were given literature-derived pre-examination probabilities (pre-EPs) for each condition and were asked to 1) estimate post-examination probabilities (post-EPs) and 2) select a diagnostic choice (either report that condition is present, order more tests to establish diagnosis, or report that condition is absent). Participants’ inverse transformed logit (ITL) mean post-EPs were compared with corresponding literature-derived post-EPs. Results Of 906 individuals invited to participate, 684 (75%) submitted a completed survey. In two of four scenarios with positive findings, the participants’ ITL mean post-EPs were significantly less than corresponding literature-derived post-EP point estimates (P <.001 for each). In three of the four scenarios consisting of negative findings, ITL mean post-EPs were significantly greater than corresponding literature-derived post-EP point estimates (P <.001 for each). In the four scenarios with positive findings, 17%–38% of participants ordered more diagnostic tests when the literature indicated a >85% probability that the condition was present. In the four scenarios with largely negative findings, 70%–85% chose to order diagnostic tests to further reduce diagnostic uncertainty. Conclusions All three groups tended to similarly underestimate the impact of examination findings on condition probability assessment, especially negative findings, and often ordered more tests when probabilities indicated that additional testing was unnecessary.

Twelve tips for teaching evidence-based physical examination

“…Applying these measures of diagnostic accuracy to estimate the ''post-test probability'' of disease allows clinicians to make rational management decisions, which may improve costeffectiveness of medical care (Shaver 1995;Zoneraich & Spodick 1995). Not surprisingly, learners and clinicians alike struggle with EBPE (Herrle et al 2011). Despite these obstacles, EBPE has been taught with success, typically in the setting of a clerkship or elective with extensive formal didactic sessions (Fagan et al 2003;Chou 2005;.…”

The role of diagnosis in delirium

“…Teaching methods from specialities such as neurology, geriatrics, and psychiatry will have much to contribute. Physicians underestimate the impact of examination findings when estimating conditional probabilities (Herrle et al, 2011), so Nicholl and Appleton have condensed the history and physical examination skills required for expertise in neurology training (Nicholl and Appleton, 2015). In older adults comprehensive geriatric assessment that considers a variety of problems is associated with better outcomes (Ellis et al, 2011).…”

A Review of the Medical Education Literature for Graduate Medical Education Teachers

“…From this group, we selected a final list of 12 articles. [1][2][3][4][5][6][7][8][9][10][11][12] A search of the National Library of Medicine's PubMed database yielded 97 articles, none of which were selected for this review from our perceptions of their relevance and quality after reading the title and abstract. The 12 chosen articles were grouped into 4 themes, shown in T A B L E 2 , and are presented below.…”

“…A cross-sectional study of medical students, IM residents, and faculty at 3 medical schools sought to determine how physical examination findings influence probability assessment and diagnostic decision making. 7 Participants were given history and preexamination probabilities for 4 conditions (ascites, congestive heart failure, streptococcal pharyngitis, and acute anterior cruciate ligament tear) and 2 separate examination scenarios (one with positive and the other with negative findings). They were then asked to estimate postexamination probabilities and make a diagnostic choice (report condition present, order more tests, or report condition absent).…”