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Differential Diagnosis1 The cornerstone of Western medicine
- 1. Differential Diagnosis Differential Diagnosis The cornerstone of The cornerstone of Western medicine Western medicine
- 2. Initial thoughts. . . Initial thoughts. . . Each question asked during the patient Each question asked during the patient interview reflects a sign, symptom, or interview reflects a sign, symptom, or risk factor for a disease that we feel may risk factor for a disease that we feel may explain the patient’s presentation. explain the patient’s presentation. Differential diagnosis directs our patient Differential diagnosis directs our patient encounter from the very beginning. encounter from the very beginning.
- 3. Patient encounter Patient encounter Differential Diagnosis History Physical Diagnostic testing Final diagnosis Static Process Static Process
- 5. Where do we begin? Where do we begin? Use available information Use available information Age Age Gender Gender Chief complaint Chief complaint Vital Signs Vital Signs Chart Review (as applicable) Chart Review (as applicable)
- 6. Thought process. . . Thought process. . . Epidemiology, Chief complaint, Vital signs Differential diagnosis Focused history and physical Refine differential diagnosis Final diagnosis Further history or physical Diagnostic testing Problem List
- 7. Studying Studying is is important! important! Understanding of epidemiology Understanding of epidemiology Age, gender, race Age, gender, race Knowledge of disease presentation Knowledge of disease presentation Which diseases present with cough, which with Which diseases present with cough, which with fever, acute versus chronic symptoms, etc. fever, acute versus chronic symptoms, etc. Ability to recognize abnormal vital signs Ability to recognize abnormal vital signs Is the patient hypertensive? Tachycardic? Is the patient hypertensive? Tachycardic? Febrile? Febrile?
- 8. Diagnosis may be made Diagnosis may be made simply. . . simply. . . Physical Vital Signs History Chief complaint Epidemiology Final diagnosis
- 9. Or not so simply. . . Or not so simply. . . Follow-up Medication Trial Diagnostic testing Formal differential Review of systems Physical History Vital Signs Chief complaint Epidemiology Final Final diagnosis diagnosis
- 10. Formal Differential Formal Differential Not needed: Not needed: Classic presentation of common disease Classic presentation of common disease Risk of acute mortality Risk of acute mortality Needed: Needed: Atypical disease presentation Atypical disease presentation Examination or testing does not confirm Examination or testing does not confirm suspected diagnosis suspected diagnosis Multiple signs and symptoms with no obvious Multiple signs and symptoms with no obvious connection connection
- 11. When you hear hoof beats. . . When you hear hoof beats. . . t think hink horses horses
- 12. Occam’s Razor Occam’s Razor A principle attributed to the 14th century A principle attributed to the 14th century logistician and Franciscan friar, William of logistician and Franciscan friar, William of Ockham Ockham “ “Pluralitas non est ponenda sine neccesitate” Pluralitas non est ponenda sine neccesitate” Plurality (numerous ideas) should not be Plurality (numerous ideas) should not be posited (considered) without necessity posited (considered) without necessity That is. . . Keep it SIMPLE!! That is. . . Keep it SIMPLE!!
- 13. Intuitive Postulates Intuitive Postulates Consider each sign or symptom individually Consider each sign or symptom individually Generate a separate differential for each of the Generate a separate differential for each of the patient’s issues patient’s issues Compare the problem-specific differentials Compare the problem-specific differentials Include diagnoses that appear frequently Include diagnoses that appear frequently Those which explain all pertinent positive findings. Those which explain all pertinent positive findings. Exclude diagnoses that appear infrequently Exclude diagnoses that appear infrequently Diagnoses that do not explain a majority of findings are Diagnoses that do not explain a majority of findings are unlikely candidates. unlikely candidates.
- 14. O/W healthy patient with. . . O/W healthy patient with. . . “cough, fever, headache, tired” “cough, fever, headache, tired” Cough Cough Fever Fever Headach Headach e e Fatigue Fatigue infection infection autoimmune autoimmune vascular vascular nutrition nutrition trauma trauma infection infection exposure exposure metabolic metabolic congenital congenital inflammatio inflammatio n n neoplasm neoplasm infection infection exposure exposure endocrine endocrine neurologic neurologic endocrine endocrine meds/drugs meds/drugs neoplasm neoplasm psychogenic psychogenic meds/drugs meds/drugs neoplasm neoplasm meds/drugs meds/drugs infection infection exposure exposure neurologic neurologic metabolic metabolic meds/drugs meds/drugs neoplasm neoplasm
- 15. How to proceed. . . How to proceed. . . Infection, neoplasm, meds/drugs, and exposure Infection, neoplasm, meds/drugs, and exposure are the most likely categories are the most likely categories Neoplasm, trauma, meds/drugs can be ruled- Neoplasm, trauma, meds/drugs can be ruled- out convincingly by further history alone out convincingly by further history alone Exposure may be difficult – is the patient aware? Exposure may be difficult – is the patient aware? DIRECT questioning – specific possibilities DIRECT questioning – specific possibilities
- 16. Proceeding. . . Proceeding. . . After ranking categories – begin to think After ranking categories – begin to think about specific diagnoses about specific diagnoses In this case – infection is most probable In this case – infection is most probable List out specific infectious etiologies List out specific infectious etiologies
- 17. INFECTION INFECTION Infectious Mononucleosis (Epstein Barr - EBV) Infectious Mononucleosis (Epstein Barr - EBV) Upper respiratory infection (rhinovirus, Upper respiratory infection (rhinovirus, paramyxovirus, etc.) paramyxovirus, etc.) Sinusitis Sinusitis Measles Measles Varicella Varicella Pneumonia Pneumonia Bronchitis Bronchitis
- 18. Making the diagnosis Making the diagnosis Using epidemiological data, history, and Using epidemiological data, history, and physical we attempt to discover the physical we attempt to discover the correct diagnosis correct diagnosis If our working diagnosis proves If our working diagnosis proves inadequate, we return to the differential inadequate, we return to the differential and start anew and start anew
- 19. Streamlined Process Streamlined Process Utilizing this more fluid thought process, as Utilizing this more fluid thought process, as each category is considered, specific diagnoses each category is considered, specific diagnoses are postulated simultaneously are postulated simultaneously As you develop the differential, more than one As you develop the differential, more than one diagnosis may be plausible diagnosis may be plausible In this case the final differential is comprised of In this case the final differential is comprised of the top possibilities in each of medical category the top possibilities in each of medical category
- 20. As illustrated here - As illustrated here - INFECTION INFECTION upper respiratory infection, sinusitis, EBV upper respiratory infection, sinusitis, EBV EXPOSURE EXPOSURE insecticides, petroleum based chemicals or fumes insecticides, petroleum based chemicals or fumes MEDICATION/DRUGS MEDICATION/DRUGS inhalant abuse, medication overdose (aspirin) inhalant abuse, medication overdose (aspirin)
- 21. Epidemiology Epidemiology The study of The study of disease disease in a specific population in a specific population Disease prevalence varies tremendously in different Disease prevalence varies tremendously in different patient populations patient populations Students should become familiar with age, gender, Students should become familiar with age, gender, and race-related disease risk and race-related disease risk In clinical study, understanding disease-specific In clinical study, understanding disease-specific epidemiology is equally important to knowledge of epidemiology is equally important to knowledge of diagnosis and treatment diagnosis and treatment
- 22. Epidemiology is essential Epidemiology is essential Sinusitis remains the most probable diagnosis in lieu Sinusitis remains the most probable diagnosis in lieu of any further information of any further information Young child who had not received standard Young child who had not received standard immunizations immunizations consider other infectious etiologies consider other infectious etiologies such as varicella or measles, along with sinusitis such as varicella or measles, along with sinusitis If this same young child had a history of exposure to If this same young child had a history of exposure to someone with either of these illnesses, consideration someone with either of these illnesses, consideration of these diagnoses would be moved ahead of of these diagnoses would be moved ahead of sinusitis altogether sinusitis altogether
- 23. Epidemiology is essential Epidemiology is essential Furthermore, the likelihood of pulmonary malignancy Furthermore, the likelihood of pulmonary malignancy in a child would be infinitesimally small in a child would be infinitesimally small 16-year-old male who had recently spent numerous 16-year-old male who had recently spent numerous sleepless nights studying for final examinations, we sleepless nights studying for final examinations, we would strongly consider EBV infection would strongly consider EBV infection A 65 year old male with a life-long history of A 65 year old male with a life-long history of construction work involving asbestos, then asbestosis construction work involving asbestos, then asbestosis or pulmonary malignancy might be considered or pulmonary malignancy might be considered before sinusitis or EBV before sinusitis or EBV
- 24. Developing a Thorough Developing a Thorough Differential Differential First review categories or areas of medicine First review categories or areas of medicine Once you had identified categories that are Once you had identified categories that are plausible, then proceed to specific diagnoses plausible, then proceed to specific diagnoses within those categories within those categories This ensures that you consider ALL possible This ensures that you consider ALL possible areas of medicine and do not just focus on areas of medicine and do not just focus on the most common the most common
- 25. VINDICATES VINDICATES V Vascular ascular I Infectious, Inflammatory nfectious, Inflammatory N Neoplastic eoplastic D Drugs rugs I Iatrogenic, Idiopathic/psychogenic atrogenic, Idiopathic/psychogenic C Congenital ongenital A Autoimmune (allergic) utoimmune (allergic) T Trauma rauma E Endocrine (metabolic/nutrition), Exposure ndocrine (metabolic/nutrition), Exposure S Systems ystems
- 26. Rank-listing the differential Rank-listing the differential Ranking of differential makes the list of Ranking of differential makes the list of diagnoses more useful diagnoses more useful Assuming that the diagnoses considered Assuming that the diagnoses considered adequately adequately explain the patient’s symptoms, explain the patient’s symptoms, the final order is based on two concepts – the final order is based on two concepts – Most common/most likely diagnosis Most common/most likely diagnosis Diseases that are associated with high mortality or Diseases that are associated with high mortality or morbidity morbidity
- 27. But what do we do with the But what do we do with the zebras? zebras?
- 28. Move uncommon disorders Move uncommon disorders higher? higher? The diagnosis is plausible in our patient The diagnosis is plausible in our patient Nearly impossible in our patient? Not necessary to consider it Nearly impossible in our patient? Not necessary to consider it from the outset – regardless of lethality. from the outset – regardless of lethality. The diagnosis can be eliminated by additional history, The diagnosis can be eliminated by additional history, physical examination, or non-invasive testing physical examination, or non-invasive testing Diagnosis requires invasive study, specialized laboratory eval. or Diagnosis requires invasive study, specialized laboratory eval. or expensive testing? It should remain toward the bottom of our expensive testing? It should remain toward the bottom of our differential list differential list The diagnosis is associated with acute mortality The diagnosis is associated with acute mortality Diagnosis is associated with mortality only after a Diagnosis is associated with mortality only after a prolonged prolonged period of time? Consideration following further evaluation of period of time? Consideration following further evaluation of more common disorders is advisable more common disorders is advisable
- 29. Sample case: Sample case: Adolescent patient with chest Adolescent patient with chest pain pain Common causes include pleurisy, costochondritis, Common causes include pleurisy, costochondritis, benign overuse myalgia, or anxiety/stress benign overuse myalgia, or anxiety/stress As such, these diagnoses should appear at the As such, these diagnoses should appear at the top top of of the differential – with specific historical and physical the differential – with specific historical and physical data influencing the final order data influencing the final order Myocardial infarction (MI), while plausible, would be Myocardial infarction (MI), while plausible, would be highly unlikely in an otherwise healthy child highly unlikely in an otherwise healthy child Therefore, MI would be placed lower on the list of Therefore, MI would be placed lower on the list of possible etiologies possible etiologies
- 30. Myocardial infarction? Myocardial infarction? Using the criteria outlined above, eliminating Using the criteria outlined above, eliminating the possibility of MI prior to final diagnosis is the possibility of MI prior to final diagnosis is a reasonable approach a reasonable approach The diagnosis is The diagnosis is plausible plausible, is , is associated associated with with acute mortality acute mortality, and can be , and can be ruled-out with a ruled-out with a minimally invasive test minimally invasive test Electrocardiogram Electrocardiogram Enzymes (CKMB/Troponin) are rarely needed Enzymes (CKMB/Troponin) are rarely needed in this scenario in this scenario
- 31. Teaching Points Teaching Points If the patient’s presentation If the patient’s presentation is is consistent with a rare consistent with a rare diagnosis, then further evaluation by whatever diagnosis, then further evaluation by whatever means necessary is compulsory means necessary is compulsory The point is not to limit our evaluation in order to The point is not to limit our evaluation in order to save money or time – instead, diagnostic evaluation save money or time – instead, diagnostic evaluation should be driven by clinical indication should be driven by clinical indication What is emphasized herein is that you must What is emphasized herein is that you must THINK THINK through the process of deciding which diagnoses are through the process of deciding which diagnoses are considered first, and which can wait. considered first, and which can wait.
- 32. The doctor as an artist The doctor as an artist Each disease process does not present in exactly the Each disease process does not present in exactly the same way every time. Medicine is more than pure same way every time. Medicine is more than pure scientific study – it is an art form scientific study – it is an art form One cannot simply memorize key facts about a One cannot simply memorize key facts about a diagnosis and limit consideration of this disease to diagnosis and limit consideration of this disease to the fulfillment of the fulfillment of all all necessary criteria alone necessary criteria alone An astute physician recognizes the possibility of An astute physician recognizes the possibility of disease presenting atypically – thereby not disease presenting atypically – thereby not explaining every sign or symptom explaining every sign or symptom
- 33. Test of time. . . Test of time. . . Having made a final diagnosis, continued observation Having made a final diagnosis, continued observation of the patient will allow us to determine if our of the patient will allow us to determine if our suspicion was correct suspicion was correct Students should recognize that uncovering the Students should recognize that uncovering the etiology of disease may require time etiology of disease may require time Early on in the course of an individual disease, limited Early on in the course of an individual disease, limited historical data and newly emerging physical findings historical data and newly emerging physical findings may make accurate diagnosis difficult may make accurate diagnosis difficult Following the patient’s clinical course or response to Following the patient’s clinical course or response to therapy may allow time for the disease to declare itself therapy may allow time for the disease to declare itself
- 34. Don’t be afraid to RE-THINK Don’t be afraid to RE-THINK If the clinical course or therapeutic response is If the clinical course or therapeutic response is not not consistent with the original diagnosis, then that consistent with the original diagnosis, then that diagnosis must be questioned diagnosis must be questioned For example, if the disease worsens unexpectedly or For example, if the disease worsens unexpectedly or the patient’s symptoms persist despite adequate the patient’s symptoms persist despite adequate medical therapy, the physician must not persist in their medical therapy, the physician must not persist in their presumption that the original diagnosis was correct presumption that the original diagnosis was correct Western physicians will turn to the medical literature or Western physicians will turn to the medical literature or their colleagues for another opinion their colleagues for another opinion
- 35. Student Student Intern Intern Resident Resident Staff Staff As they are just beginning their medical As they are just beginning their medical training, students have a less exhaustive training, students have a less exhaustive understanding of disease presentation, and so understanding of disease presentation, and so cannot narrow their history and physical to cannot narrow their history and physical to only the most relevant topics only the most relevant topics With time and experience the student becomes With time and experience the student becomes more adept at the process of obtaining a more adept at the process of obtaining a relevant, focused history, performing a relevant, focused history, performing a directed physical examination, and the like directed physical examination, and the like
- 36. Student Student Intern Intern Resident Resident Staff Staff With time, students learn to incorporate With time, students learn to incorporate a dynamic approach to the differential a dynamic approach to the differential diagnosis diagnosis This allows them to reassess diagnostic This allows them to reassess diagnostic possibilities throughout the entire possibilities throughout the entire process – not just after the basic process – not just after the basic information has been obtained information has been obtained
- 37. Dynamic Process Dynamic Process This intuitive style of thinking has been ingrained into the minds This intuitive style of thinking has been ingrained into the minds of Western physicians of Western physicians The process begins at the onset of the patient’s presentation The process begins at the onset of the patient’s presentation and then drives the entire patient encounter – directing further and then drives the entire patient encounter – directing further questioning, examination, and diagnostic testing questioning, examination, and diagnostic testing In cases where clinical course or response to therapy is In cases where clinical course or response to therapy is inconsistent with the original diagnosis, return to the inconsistent with the original diagnosis, return to the differential leads the physician in a new direction differential leads the physician in a new direction In every sense of the word, differential diagnosis is a In every sense of the word, differential diagnosis is a dynamic dynamic process. process.