Differential Diagnosis Generation


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"How I learned to stop worrying and love the BALM:" a method to developing a differential diagnosis

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  • Examples: headache/CP/SOB. D-dimer, nitrazine test, amylase
  • Heuristics
  • Differential Diagnosis Generation

    1. 1. Differential Diagnosis<br />Or “How I learned to stop worrying and love the BALM”<br />Clinton Pong<br />
    2. 2. Objectives<br />Define “differential diagnosis”<br />Errors<br />aka how do you get the “right ddx”<br />Develop a systematic, routine method for differential diagnosis generation<br />The BALM<br />
    3. 3. The Challenge: What is a Ddx?<br />Recognize a collection of signs and symptoms<br />Recall basic pathophysiology<br />Restate in terms of disease<br />Reconnect with the initial complaint<br />Framing: pre-/post-test probability<br />Reframing: Reconsidering ddx when there is a progression of unusual natural history<br />
    4. 4. How many times have you done this?<br />Premature closure of diagnosis<br />“Hm, this is the cardio unit and they have chest pain. Duh. It’s a heart attack.”<br />The crazy “House” diagnosis<br />“Chest pain and shortness of breath?!? They could have a worm like Strongyloidesstercoralis that went up their gut into their lungs and then to their bloodstream!”<br />The LI of the MINDNUMBING table of differentials A-Z + 1,2,3,4,5,6,7,8,9,10…<br />
    5. 5. Cognitive Diagnostic Errors<br />Examples:<br />“Umm… trauma or cancer?”<br />“80 years old? I thought you said 18 years old.”<br />“Psh. It’s just a little ____.”<br />“The ___ is (+) so it is ____.”<br />“The __ is (-) so it is not __.”<br />“It’s gotta be a ____.”<br />Errors<br />Faulty hypothesis generation<br />Faulty context formulation<br />Faulty information gathering/processing<br />Inaccurate assessment of prevalence or severity<br />Wrong interpretation of test<br />Overrreliance on clinical axiom<br />Faulty verification<br />Premature closure of diagnosis<br />“No-fault” errors<br />
    6. 6. Many diagnostic errors occur because we try<br /> to fit the data to our hypothesis rather than<br /> fitting the hypothesis to our data.<br />http://www.flickr.com/photos/epublicist/<br />
    7. 7. http://hlwiki.slais.ubc.ca/index.php?title=Long_tail#Impact_in_medicine<br />http://www.medrants.com/?p=3629<br />
    8. 8. House, MD. White board<br />http://differentialdiagnosi.proboards.com/index.cgi?<br />
    9. 9. Occam’s Razor:Quest for the Holy Parsimony<br />“Plurality should not be posited without necessity.”<br />Pluralitas non estponenda sine necessitate<br />http://en.wikipedia.org/wiki/William_of_Ockham<br />
    10. 10. Sherlock Holmes<br />&quot;When you have eliminated the impossible, whatever remains, however improbable, must be the truth.&quot;<br />
    11. 11. DeGowin’s Quotable:<br />Disease is a four-dimensional story, which follows the biologic imperatives of its particular pathophysiology in specific anatomic sites as influenced by the unique characteristics of this patient.<br />Your task is not verbal, but cinematic; construct a pathophysiologic and anatomic movie of the onset and progression of the illness: the words are generated from the images, not the images from the words. <br />
    12. 12. Nobody ever needs to know that the instant you see lawyer [on the USMLE] you immediately think:<br /> “Scumbag who sleeps with prostitutes and therefore has gonorrhea, syphilis, chlamydia, and herpes.”<br />It’ll stay our dirty little secret.<br />http://www.agraphia.net/zac-fact-10-bigot-your-way-to-success/<br />
    13. 13. Race/Ethnicity<br />African Americans have sarcoid and sickle cell.White kids have cystic fibrosis and can’t dance.Japanese people have stomach cancer and ninja skills.<br />Lifestyles<br />Women are always pregnant. No matter how careful they were.Coke Addicts had an MI (don’t smoke crack, kids!)Patients with a swollen knee are female, young, hot, and caught gonorrhea from their last boyfriend.<br />Etc…<br />http://www.agraphia.net/zac-fact-10-bigot-your-way-to-success/<br />
    14. 14. The BALM<br />By systems<br />Acute vs Chronic<br />Local vs Systemic<br />MEDICINE DOC<br />Great tier system for starting off your ddx<br />Where is it?<br />Will it kill the patient?<br />What else can it do?<br />If all else fails, go to the laundry list.<br />
    15. 15. Framework<br />AcutevsChronic<br />LocalvsSystemic<br />High Probability – Incidence<br />(the most difficult part of the frame as a medical student)<br />What is most likely? Rare  Common<br />High Utility – Morbidity/Mortality<br />What do you want to make sure you never miss? Benign  Serious<br />
    16. 16. The Systems Approach<br />MEDICINE<br />Metabolic/Medications<br />Endocrine<br />Degenerative<br />Infection/Ischemia/Infarction<br />Congenital<br />Iatrogenic/Idiopathic<br />Neoplastic<br />Electrical (Neuro/Psych)<br />Alternatively,<br /><ul><li>I VINDICATE AID
    17. 17. DIRECTION
    18. 18. VITAMIN C,D</li></ul>PE organ systems list<br />Neuro<br />Lung<br />CV<br />GI<br />Renal/GU/GYN<br />Heme/ID<br />Endo<br />
    19. 19. The Systems Approach<br />VITAMIN C, D & E<br />Vascular<br />Infection/Ischemia/Infarction<br />Trauma/Toxin<br />Autoimmune<br />Metabolic/Medications<br />Iatrogenic/Idiopathic<br />Neoplastic<br />Congenital<br />Degenerative<br />Electrical (Neuro/Psych)<br />Alternatively,<br /><ul><li>I VINDICATE AID
    20. 20. DIRECTION
    21. 21. MEDICINE</li></ul>PE organ systems list<br />Neuro<br />Lung<br />CV<br />GI<br />Renal/GU/GYN<br />Heme/ID<br />Endo<br />
    22. 22. By discipline<br />Hint hint…<br />
    23. 23. Resources<br />Groopman, Jerome. How Doctors Think. Mariner Books © 2008.<br />Kassirer, Jerome. Learning Clinical Reasoning. Williams and Wilkins. © 1991.<br />DeGowin&apos;s Diagnostic Examination, Ninth Edition (Paperback) by Richard LeBlond (Author), Donald Brown (Author), Richard DeGowin (Author)<br />http://en.wikipedia.org/wiki/William_of_Ockham<br />(Heuristics) Bigot your way to Success on the USMLE<br />http://www.agraphia.net/zac-fact-10-bigot-your-way-to-success/<br />“Separating clinicians from automatons: the long tail”<br />http://doctorrw.blogspot.com/2008/08/separating-clinicians-from-automatons.html<br />