A Priori Diagnosis and Diagnostic Errors
A Priori Diagnosis and Diagnostic Errors
This is a prospective randomized single-blind simulator-based trial. 156 4th year medical
 students were randomised to receive one of three different suspected diagnoses of a
 pre-treating physician (no diagnosis, myocardial infarction, pulmonary embolism) prior to the
 task to make a focussed assessment and perform first management steps in a patient presenting
 to the emergency department. The patient (simulator) suffered from an acute myocardial
 infarction. Video recordings were obtained during simulation and used for data analysis.
 Primary endpoint was the participants' final presuptive diagnosis.
Methods:

 Study design:

 This is a prospective randomized controlled single-blind trial, the participants not being
 aware of the purpose of the study. The trial was approved by the regional ethical committee
 (EKNZ 85/04) and all participants gave written informed consent.

 Participants:

 Medical students in their 4th year at the University of Basel, Switzerland were offered to
 participate in voluntary workshops at the simulator centre of the medical intensive care unit
 of university of Basel hospital. The present study was conducted as part of these workshops.

 At the beginning of the workshop participants were asked to fill in a questionnaire. The
 questionnaire included a) the Big Five personality traits (neuroticism, extraversion,
 openness, agreeableness, conscientiousness) (McCrae 1992); b) Rosenberg's self-esteem
 scale(Colani); c) the task to diagnose the cardiac rhythm in 12 one-lead ECG rhythms strips
 (each correct diagnosis was counted as one point resulting in a maximum of 12 attainable
 points); d) the task to list the typical symptoms of an acute myocardial infarction in bullet
 point form (each of the following items were counted as one point resulting in a maximum of 6
 attainable points: chest pain; radiation of the pain; pain described as constricting,
 compressing, or squeezing; at least one accompanied vegetative symptom; dyspnoea; and fear);
 and e) the task to list the typical signs symptoms of 4 further medical emergencies
 (anaphylactic shock, trauma management, cardiac arrest, syncope) in bullet point form
 (answers were coded using a predefined checklist).

 Simulator and Scenario:

 The study was conducted using a patient simulator. All participants received a standardised
 instruction of the patient simulator (human patient simulator, Leardal SimMan®). This
 simulator's features include among others palpable pulses, spontaneous breathing with visible
 thoracic excursions, spontaneous movements of the eye lids and a speaker in the mannequin's
 head that broadcasts the voice of a remote operator, allowing for verbal interaction with the
 participants. For the present trial, the operator was an experienced physician.

 For the study scenario participants were given the role of a resident-on-call in the
 emergency department and were instructed by a senior physician (confederate) to triage a
 newly arrived patient. Upon entering the simulator room, the participants encountered the
 patient (simulator) lying on a bed and dressed in a hospital gown. Participants were assisted
 by a confederate nurse. The nurse was instructed to display a helpful manner, to act only on
 command, but not to interfere in any way with the assessment and history taking.

 Intervention:

 All participants performed the scenario on their own and faced a patient with a simulated
 acute myocardial infarction. Participants were randomized (computer-generated numbers) to
 three versions of the scenario. The three versions differed only in the reply of the patient
 to the initial question about the reason for his visit. The patient volunteered that he had
 phoned his family physician because of acute chest pain and dyspnoea. The family physician
 had recommended urgent visit of the emergency department because he judged the situation as
 1) medical emergency (control group with no à priori diagnosis); 2) acute myocardial
 infarction (correct à priori diagnosis group); or, 3) acute pulmonary embolism (wrong à
 priori diagnosis group). Apart from this randomly allocated initial information, the scenario
 was identical in all groups: until the end of the scenario, the patient only spoke when asked
 a question and all answers were given according a pre-scripted answer check-list (table)
 Participants of the groups with no à priori diagnosis and correct à priori diagnosis were
 given 4 minutes study time. Participants of the group with wrong diagnosis were given one
 additional minute (i.e. 5 minutes study time) to compensate for probing the given diagnosis.
 At the end of the study time, the senior physician entered the room and announced that he
 required the participant to temporarily leave his/her patient to help with another emergent
 case. The participants were then asked on their presumptive diagnosis and which measures, if
 any, the nurse should take during their temporary absence during the next couple of minutes.

 Data analysis:

 Data analysis was performed using video recordings obtained during simulations. Video
 recordings were analysed independently by two trained raters who noted all questions asked
 and all measures taken by the participant. Inter-observer differences were solved by jointly
 re-watching the video recordings.

 Statistics:

 The primary endpoint was a correct presumptive diagnosis of an acute myocardial infarction or
 acute coronary syndrome when asked at the end of the scenario by the senior physician or when
 previously revealed to the patient and/or the nurse. Mentioning the correct diagnosis as
 possible differential diagnosis was rated as correct diagnosis. A co-primary endpoint was the
 composite endpoint of a correct presumptive diagnosis OR ordering a 12-lead ECG, the
 rationale being that a timely 12-lead ECG will most likely prevent harm to a patient not
 correctly triaged as suffering from acute myocardial infarction.

 Secondary endpoints were the number and kind of questions asked during history taking;
 probing of the à priori diagnosis; measures taken during assessment; and the results of the
 questionnaire. Results of the knowledge part of the questionnaire are reported as percentages
 of the attainable maximum.

 A 20% difference in the primary outcome was considered to be of medical relevance- A power
 analysis revealed that approximately 150 teams (50 per group) had to be included to detect
 this difference with a power of 0.9 at the 0.05 significance level.

 Statistical analysis was performed by SPSS (version 25). Non-parametric ANOVA, Mann-Whitney
 test, chi-square test, Univariate and Multivariate regression analysis, and Cohen's kappa
 were used as appropriate. A p < 0.05 was considered to represent statistical significance.
 Data are reported as median [Interquartile range {IQR}] unless otherwise stated.
Inclusion Criteria:

 -  4th year medical students and physicians taking part in simulation workshops

 Exclusion Criteria:

 -  no consent given to video-tape simulation and analyse vide recordings for scientific
 purpose