2. Learning objectives
• Define what it means to create a differential diagnosis
• Explain the information that goes into creating a
differential diagnosis
• Establish a method for developing a differential
diagnosis
• Prioritize items within the differential diagnosis by
integrating likelihood and danger of missing an
important diagnosis
3. Goals of the Differential Diagnosis
• Guide evaluation and treatment
• Generate working diagnoses
• Rule out life-threatening and time-critical conditions
• Make the correct diagnosis
5. Approach to the Differential Diagnosis
• Two general approaches identified:
• Pattern Recognition (Intuitive)
• Analytic (Hypothesis-Driven)
• Approaches overlap and combinations of both are used in
practice (“dual processing”)
• Both approaches subject to error from cognitive biases
6. Approach to the Differential Diagnosis
• Pattern Recognition (Intuitive):
• Match your overall patient assessment to your internal data bank of
how diseases present
• “This looks like a patient with pneumonia…”
• Can happen rapidly/almost unconsciously
7. Approach to the Differential Diagnosis
• Analytic (Hypothesis-Driven):
• Hypothesis generation can be
based on intuition, probability,
pathophysiology, etc.
• Test a small number of
hypotheses at one time
Collect
Information
Analyze and
Synthesize Data
Generate/Test
Hypotheses
(Differential)
8. Overall steps in the diagnostic process
Collect data
Develop a
differential
diagnosis (DDx.)
Diagnostic
testing
Final diagnosis
As diagnostic tests become
available, the results become
additional information that
hopefully narrows the
differential diagnosis.
9. The ideal differential diagnosis
Should include:
1. The diagnosis you feel is most likely, i.e. the working
diagnosis
2. Several other (often 2-4) other diagnoses worth considering
– the patient could have either a typical or an atypical
presentation; these should ideally be prioritized in
descending order of likelihood
3. Any “do not miss diagnoses,” i.e. diagnoses with serious
consequences (even potentially fatal) if missed
10. Steps in developing a differential diagnosis
1. Acquire data: from patient history, physical examination,
additional objective information initially available (e.g., lab or
imaging studies, old records, information from family)
2. Identify key features: elements of the presentation that may help
differentiate one diagnosis from another; both positive and
negative findings
3. Create a problem summary: develop a 1-2 sentence summary,
using appropriate medical terminology, of the most highly relevant
aspects of the history, exam, and available diagnostic tests
11. Useful descriptors when developing a summary
• Onset
• Abrupt or progressive
• Acute or chronic
• Course: continuous or episodic
• Site
• Unilateral or bilateral
• Proximal or distal
• Diffuse or localized
• Symptom trigger: post-prandial, exertional, pleuritic, positional
• Presence of pain: painful or painless
12. Using medical terminology to summarize
Develop a summary for each of the following patient statements:
1. “For the last 30 minutes, my chest has hurt whenever I
take a deep breath”
2. “Over the past several months, both legs have been
getting weaker and weaker”
13. Using medical terminology to summarize
Develop a summary for each of the following patient statements:
1. “For the last 30 minutes, my chest has hurt whenever I
take a deep breath”
Summary: Acute pleuritic chest pain
2. “Over the past several months, both legs have been
getting weaker and weaker”
Summary: Chronic, progressive bilateral lower extremity weakness
14. Steps in developing a differential diagnosis
1. Acquire data: from patient history, physical examination, additional
objective information initially available (e.g., lab or imaging studies,
old records, information from family)
2. Identify key features: elements of the presentation that may help
differentiate one diagnosis from another; both positive and negative
findings
3. Create a problem summary: develop a 1-2 sentence summary,
using appropriate medical terminology, of the most highly relevant
aspects of the history, exam, and available diagnostic tests
4. Synthesize findings into a clinical formulation of the problem(s)
15. Steps in developing a differential diagnosis
1. Acquire data: from patient history, physical examination, additional
objective information initially available (e.g., lab or imaging studies,
old records, information from family)
2. Identify key features: elements of the presentation that may help
differentiate one diagnosis from another; both positive and negative
findings
3. Create a problem summary: develop a 1-2 sentence summary,
using appropriate medical terminology, of the most highly relevant
aspects of the history, exam, and available diagnostic tests
4. Synthesize findings into a clinical formulation of the problem(s)
5. Develop the prioritized list of diagnoses to be included in the
differential
16. Working through an example
• This example will provide individual bits of information
• You should work through the 5 steps in developing a differential
diagnosis
1. Acquire data – this will be provided for you
2. Identify key features
3. Create a problem summary
4. Synthesize findings into a clinical formulation
5. Develop the prioritized list of diagnoses to be included in the differential
• The goal of this exercise is to understand how to do each of the
steps, not necessarily to get the correct diagnosis
17. Case presentation: history as obtained
62 year old male presents because of abdominal pain. He says it
started about 6 hours ago and is pretty severe. He has also been sick
to his stomach and has vomited twice. The pain is mostly in the upper
central part of his abdomen. It is constant, and nothing seems to
make it better or worse. He has not had diarrhea or constipation and
has not noticed any change in stool color.
His medical problems have included hypertension and diabetes. He
usually drinks 2-3 beers per day, and he has smoked 1 pack per day
for 30 years. He has never been an injection drug user.
Medications are hydrochlorthiazide and metformin.
He is married and lives with his wife. He has 2 grown children who
are healthy. He has worked in construction and is exposed to a
significant amount of dust.
19. Question for discussion
What is the key information from the history?
• 62 year-old male
• Acute severe abdominal pain
• Location: central upper abdomen (epigastrium)
• Nausea and vomiting
• History of diabetes and hypertension
• Moderate alcohol use
20. Case presentation: physical examination
On examination, he appears to be in moderate distress from the pain.
Vital signs: P 104 and regular, BP 130/80, R 22, T 38.2o
C., SpO2
95%. Skin without rashes or lesions. HEENT examination: normal.
Neck examination without lymphadenopathy. Normal carotid pulses;
no jugular venous distention. Chest examination: a few crackles at
both bases that cleared after coughing. Cardiac examination: regular,
no murmur. Abdomen soft, without rebound. There was significant
epigastric tenderness. Liver and spleen were not enlarged. Rectal
examination negative; stool negative for occult blood. Extremities
without cyanosis, clubbing, or peripheral edema. Neurologic
examination: mental status normal; cranial nerves normal. Motor
exam normal. Decreased light touch and pinprick sensation in feet.
Reflexes 2+ except absent ankle reflexes.
22. Question for discussion
What are the key elements from the physical
examination?
• Moderate distress
• Low-grade fever and tachycardia
• Epigastric tenderness without rebound
• Sensory and reflex changes in feet – but likely not
relevant here
23. Summary of key information
History
• 62 year-old man
• Acute severe abdominal pain
• Onset 6 hours ago
• Localized to epigastrium
• Constant
• Nothing makes better or
worse
• Nausea and vomiting
• No change in bowel habits
Past history and social history:
• Hypertension
• Diabetes
• Moderate alcohol use
• Smoking
Physical examination:
• Moderate distress
• T 38.2o
C., P 104, R22
• Epigastric tenderness, no rebound
• Sensory and reflex findings in feet
24. Question for discussion
Create a problem summary of the information relevant
to his presentation. Try creating one sentence for the
history and one sentence for the physical examination.
25. Question for discussion
Create a problem summary of the information relevant
to his presentation. Try creating one sentence for the
history and one sentence for the physical examination.
62 year old male with underlying diabetes and
hypertension who presents with a 6-hour history of
constant and severe epigastric pain accompanied by
nausea and vomiting. On physical examination, he is
febrile to 38.2o
C. and has epigastric tenderness without
rebound.
27. Question for discussion
Synthesize the information into a clinical
formulation of the current, active problem(s).
1. Acute severe epigastric pain and tenderness
with nausea and vomiting
2. Low-grade fever
28. Putting together the differential diagnosis
• Start with what seems to be the most important problem
• In this case, the most important problem is the epigastric pain
• Put together a list of items that can lead to epigastric pain
and may be associated with nausea and vomiting
• Look at the other important piece of information
• In this case, the other important information is the patient’s low-
grade fever
• Does the presence of fever go for or against any of the items
on your list of causes of epigastric pain?
29. Starting to make the differential diagnosis
One approach is to make a list of structures that can cause
pain in the epigastric region.
For discussion, start by listing the potentially relevant
structures:
30. Starting to make the differential diagnosis
One approach is to make a list of structures that can cause
pain in the epigastric region.
For discussion, start by listing the potentially relevant
structures:
Stomach
Esophagus
Intestine, small or large
Pancreas
Biliary tree
Heart
Soft tissue of abdominal wall, e.g., muscle
31. Continuing to create the differential diagnosis
Now list some specific disorders relating to these structures
that could cause epigastric pain:
1. Stomach:
2. Esophagus:
3. Intestine:
4. Pancreas:
5. Biliary tree:
6. Heart:
7. Soft tissue of abdominal wall:
32. Continuing to create the differential diagnosis
Now list some specific disorders relating to these structures
that could cause epigastric pain:
1. Stomach: gastritis or peptic ulcer disease, gastroenteritis
2. Esophagus: esophagitis, gastroesophageal reflux
3. Intestine: bowel ischemia or infarction, intestinal obstruction,
inflammatory bowel disease, peptic ulcer disease
4. Pancreas: acute pancreatitis
5. Biliary tree: cholelithiasis, choledocholithiasis
6. Heart: myocardial ischemia or infarction
7. Soft tissue of abdominal wall: muscle strain
33. Refine the differential diagnosis
Try to tie in the other important pieces of information:
• Does the presence of nausea and vomiting go for or against
any diagnoses?
.
• Does the presence of fever go for or against any diagnoses?
• Do any of the diagnoses on your list go particularly well with
epigastric pain, nausea and vomiting, and fever?
34. Refine the differential diagnosis
Try to tie in the other important pieces of information:
• Does the presence of nausea and vomiting go for or against
any diagnoses?
Nausea and vomiting goes against a musculoskeletal etiology.
• Does the presence of fever go for or against any diagnoses?
Fever suggests either inflammation or infection. This means it would be in
favor of diagnoses such as gastroenteritis, acute pancreatitis, cholecystitis
(related to a stone)
• Do any of the diagnoses on your list go particularly well with
epigastric pain, nausea and vomiting, and fever?
This is particularly characteristic of pancreatitis, which should be high on the
list.
35. Our preliminary differential diagnosis list
Now create your initial differential diagnosis list, and prioritize
by starting with your leading diagnostic possibility:
36. Our preliminary differential diagnosis list
Now create your initial differential diagnosis list, and prioritize
by starting with your leading diagnostic possibility:
1. Acute pancreatitis – leading possibility
2. Gastroenteritis
3. Peptic ulcer disease
4. Bowel infarction
5. Myocardial ischemia or infarction – not high on the list, but it is a “do
not miss” diagnosis so should be included on the list
Note: inflammatory bowel disease and obstruction less likely in the
absence of change in bowel habits.
37. What happens now?
• Diagnostic studies to confirm or refute possible diagnoses
• With pancreatitis highest on the list, initial studies would include
pancreatic enzymes (amylase, lipase), which are elevated in
pancreatitis
• Myocardial ischemia and infarction should be evaluated with
electrocardiogram and cardiac biomarker (troponin)
• If pancreatic enzymes are normal, then proceed with evaluation of
luminal GI tract
• In this case, amylase and lipase are elevated, confirming the
diagnosis of acute pancreatitis
38. Another approach to developing a differential
• The approach we just covered was a structural approach to
having a systematic way of developing a differential diagnosis
• Another useful approach uses a framework of categories of
disease
• This approach is useful after structures or sites of disease have been
identified
• It is also particularly useful for multisystem disease, where more than
one site or organ system is involved.
• A useful framework for thinking about sites of disease has
been presented using a variety of different mnemonics
• One mnemonic is presented in the next slide
39. Different categories of disease: using a mnemonic
V = vascular
I = infection/inflammation
T = trauma/toxins
A = autoimmune
M = metabolic
I = idiopathic
N = neoplasia
C = congenital
D = degenerative
E = endocrine or exocrine
VITAMINCDE
40. Example using categories of disease approach
Case scenario: a patient with unilateral hip pain
For discussion: Try using the categories of
disease approach (using the VITAMINCDE
mnemonic) to develop a differential diagnosis
for a patient with unilateral hip pain. Include at
least 1 possible diagnosis for each of the letters
in the mnemonic.
41. Example using categories of disease approach
Vascular: avascular necrosis of
the hip
Infection: septic arthritis
Trauma: hip fracture
Autoimmune: rheumatoid
arthritis
Metabolic: gout
Idiopathic: nonspecific
musculoskeletal strain
Neoplastic: bone or soft tissue
tumor
Congenital: congenital hip
dysplasia
Degenerative: osteoarthritis
Endocrine or exocrine:
osteoporosis
Case scenario: a patient with unilateral hip pain
42. Learning objectives
• Define what it means to create a differential diagnosis
• Explain the information that goes into creating a
differential diagnosis
• Establish a method for developing a differential
diagnosis
• Prioritize items within the differential diagnosis by
integrating likelihood and danger of missing an
important diagnosis
