this module will guide you in how to use the assessment of reasoning tool to assess a learner's ability to construct a prioritized differential diagnosis a prioritized differential diagnosis is a probability ranking of the diagnosis that a clinician is considering based on how well they match the problem representation a clinician should first select the leading hypothesis and consider can't-miss hypotheses then they should consider less likely and unlikely alternative hypotheses as a reminder from module 2 the problem representation is a concise synthesis of the clinical problem that needs to be solved it captures information for the following three questions who is this patient what is the clinical syndrome what is the time course clinicians compare and contrast potential diseases described as illness scripts in alignment with the problem representation the closer the match between the problem representation and the illness script the more likely it is that the selected disease is the explanation for the patient's presentation the ranking of the diagnosis should be accompanied to by the clinical evidence that increases or decreases the likelihood of each proposed diagnosis in addition some consideration is expected for the most serious or emergent diseases on the differential diagnosis or can't-miss diagnosis an evaluator can monitor the learners ability to reason by analyzing their spoken or written assessment for the patient's main problems let's look at a case now to show you how to use the AR T to assess a learner's ability to construct a prioritized differential diagnosis Julio Martinez is a 27 year old woman with hyperthyroidism with two days of nausea vomiting diarrhea and left upper quadrant pain but no abdominal tenderness fever or leukocytosis the following is an example of a high performer which you would mark as complete on the AR T your learner gives the following report of a patient the most likely diagnosis is viral gastroenteritis bass the combination of nausea vomiting and diarrhea and the acuity less likely is food poisoning because no one she dined with is sick the location in diarrhea make appendicitis unlikely ectopic pregnancy is a can't-miss diagnosis in young women with abdominal pain in this example the learner starts by marking tiers of probability clearly with phrases such as most likely less likely and unlikely a can't-miss ectopic pregnancy diagnosis is also mentioned he also gives the evidence for and against each condition the following is an example of a low performer which you would mark as partial on the AR T this patient has abdominal pain nausea vomiting and diarrhea and each has a broad differential diagnosis I think appendicitis ectopic pregnancy and food poisoning are all possible and explain most of the symptoms although it is not a really good story for appendicitis or ectopic pregnancy I would check a urine pregnancy while we give IV fluids and supportive care in this example the learner lists reasonable diagnoses to consider and acknowledges emergent conditions however he does not delineate the relative probabilities of diagnoses and does not suggest evidence for or against each diagnosis in summary a prioritized differential diagnosis ranks diseases based on how well they match the problem representation a prioritized differential diagnosis should include can't-miss diagnosis to ensure that the learner has considered them a well-articulated prioritized differential diagnosis has supporting and refuting evidence for each diagnosis you