Transcript pptx

Designing USMLE-style
scenarios and questions
Eric Niederhoffer
SIU-SOM
Outline
• USMLE style
• Scenario template
• Resources
• Clinical pearls
• Example designs
USMLE Style
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Focus on important concept, not trivial facts
Assess application of knowledge, not isolated recall
Avoid giving facts that may be used elsewhere on exam
Avoid defining terms or drugs that should be in knowledge base
Pose a clear question with one best answer
Provide homogeneous distractors (incorrect options)
Avoid technical flaws or clueing
Five answer choices (or balanced)
Scenario Template
• A n-year-old (Age) boy/girl/man/woman (Gender) comes/is
brought to the physician/emergency department (Site of Care)
for evaluation of/with a problem (Presenting Complaint including
Duration and Patient/Family History).
• Physical examination shows some combination of pertinent
findings (Height/Weight/BMI/Percentile, Temperature/Heart
Rate/Breathing Rate/Blood Pressure).
• Laboratory studies show some combination of test results
(Reference Ranges provided for non-adult age groups/special
tests).
• Which drug, toxic exposure, diet; predict physical findings, lab
findings, sequelae; identify underlying
cause/mechanism/diagnosis, cause of drug response, drug to
administer (Questions)
Resources
• Textbooks with clinical correlations
• Internet sites for selected diseases
emedicine.com
Harrison’s eSupplement
NCBI endocrinology
Online pathology cases
• Primary literature
• Reference ranges for ages/gender (pediatric)
Clinical Pearls
“Pink Puffer”
A person where emphysema is the primary underlying pathology. There has been
gradual destruction of the pulmonary capillary bed and decreased ability to
oxygenate the blood. Less surface area for gas exchange, less vascular bed for
gas exchange--but less ventilation-perfusion mismatch than blue bloaters. The
person compensates by hyperventilation (the "puffer" part). Arterial blood gases
are relatively normal. Because of the low cardiac output, patients develop muscle
wasting and weight loss. Less hypoxemia (compared to blue bloaters) and appear
to have a "pink" complexion. No right sided heart failure signs.
pH
increased
PCO2
decreased-normal mm Hg
PO2
>60 (70) mm Hg
HCO3decreased mEq/L
DLCO
decreased
Clinical Pearls
“Blue Bloater”
A person where the primary underlying lung pathology is chronic bronchitis.
Caused by excessive mucus production with airway obstruction resulting from
hyperplasia of mucus-producing glands, goblet cell metaplasia, and chronic
inflammation around bronchi. Pulmonary capillary bed is undamaged. Body
responds by decreasing ventilation and increasing cardiac output. Poor ventilationto-perfusion mismatch leading to hypoxemia and polycythemia. There is increased
carbon dioxide retention (hypercapnia). Because of increasing obstruction, residual
lung volume gradually increases (the "bloating" part). Hypoxemic/cyanotic
manifests as bluish lips and faces--the "blue" part. Right-sided heart failure,
peripheral edema, systemic venous congestion, elevated hematocrit and
respiratory acidosis are characteristic. Sputum, coughing and infections are
general features.
pH
decreased
PCO2
>45 (increased) mm Hg
PO2
<60 (decreased) mm Hg
HCO3increased mEq/L
Disease or Condition Approach
(Piriformis Syndrome)
• Find additional information about PS from
emedicine
• Search (piriformis syndrome “clinical case”)
for an appropriate clinical case (review) to
abstract
• Consider what relevant concept or content
to assess
• Design a specific question (use diagrams)
• Provide balanced homogeneous distractors
Piriformis Syndrome
A 36-year-old woman comes to the physician with a 1-week history
of pain in the right buttocks that radiates to the right lower leg. She
has tried aspirin, but the pain persists. Physical examination
shows pain present in the vicinity of the greater sciatic notch during
extension of the knee with the hip flexed to 90º, tenderness to
palpation of the greater sciatic notch, and a sausage-shaped mass
over the piriformis muscle. The woman is given an injection of
bupivacaine hydrochloride (amide anesthetic) intramuscularly and
is treated with naproxen. She is provided instructions for rest along
with gentle muscle stretching.
Where do we go from here?
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Ask mechanism of action for medications.
Ask which receptors are involved.
Piriformis Syndrome #1
A 36-year-old woman comes to the physician with a 1-week history of
pain in the right buttocks that radiates to the right lower leg. She has
tried aspirin, but the pain persists. Physical examination shows pain
present in the vicinity of the greater sciatic notch during extension of the
knee with the hip flexed to 90º, tenderness to palpation of the greater
sciatic notch, and a sausage-shaped mass over the piriformis muscle.
The woman is given an injection of bupivacaine hydrochloride (amide
anesthetic) intramuscularly and is treated with naproxen. She is
provided instructions for rest along with gentle muscle stretching.
The mechanism of action for the medication that the patient initially tried
most likely increases the concentration of which of the following labeled
molecules?
A.
B.
C.
D.
E.
A
B
C
D
E
Piriformis Syndrome #2
A 36-year-old woman comes to the physician with a 1-week history of
pain in the right buttocks that radiates to the right lower leg. She has
tried aspirin, but the pain persists. Physical examination shows pain
present in the vicinity of the greater sciatic notch during extension of the
knee with the hip flexed to 90º, tenderness to palpation of the greater
sciatic notch, and a sausage-shaped mass over the piriformis muscle.
The woman is given an injection of bupivacaine hydrochloride (amide
anesthetic) intramuscularly and is treated with naproxen. She is
provided instructions for rest along with gentle muscle stretching.
The mechanism of action for one of the medications used to treat
the patient inhibits an enzyme that most likely synthesizes which of
the following labeled molecules?
A.
B.
C.
D.
E.
F.
G.
A
B
C
D
E
F
G
Piriformis Syndrome #3
A 36-year-old woman comes to the physician with a 1-week history of
pain in the right buttocks that radiates to the right lower leg. She has
tried aspirin, but the pain persists. Physical examination shows pain
present in the vicinity of the greater sciatic notch during extension of the
knee with the hip flexed to 90º, tenderness to palpation of the greater
sciatic notch, and a sausage-shaped mass over the piriformis muscle.
The woman is given an injection of bupivacaine hydrochloride (amide
anesthetic) intramuscularly and is treated with naproxen. She is
provided instructions for rest along with gentle muscle stretching.
The mechanism of action for the medication that the patient initially tried increases the
concentration of a molecule that most likely binds to which of the following labeled receptors?
A.
B.
C.
D.
E.
F.
G.
H.
A
B
C
D
E
F
G
H
Relevant Concept Approach
(Glycoprotein Structure/Function)
• Find information about abnormal/defective
glycoproteins from reference sources
• Search emedicine for appropriate diseases
to consider
• Construct a brief scenario representative of
common presentation
• Design a specific question
• Provide balanced homogeneous distractors
Glycoproteins
Glycoprotein
Disease/Condition
Antibodies
immunoglobulin A deficiency, autosomal dominant
hyperimmunoglobulin E (Job) syndrome
Blood group antigens
transfusion
Collagen
Alport syndrome, vitamin C deficiency (scurvy)
Fibrillin
Marfan syndrome, isolated ectopia lentis
Glycoprotein IIb/IIIa
immune thrombocytopenic purpura, Glanzmann
thrombasthenia
Mucins
scleredema, asthma
Thyroid stimulating hormone
goiter, thyroxine-binding globulin deficiency
Concept Approach #1
Goiter
A 37-year-old woman comes to the physician with a 6-month history of neck discomfort. A photo of the
patient is shown.
Laboratory serum studies show:
TSH
24 µU/mL (N=0.5-5.0)
Thyroxine (T4)
22 µg/dL (N=5-12)
Analysis of the protein hormone will most likely show which of the following co- and post-translational
modifications?
A.
B.
C.
D.
E.
F.
G.
H.
Acylation
Alkylation
Biotinylation
𝛾-Carboxylation
Glycosylation
Hydroxylation
Isoprenylation
S-Nitrosylation
Concept Approach #2
Goiter
A 37-year-old woman comes to the physician with a 6-month history of neck discomfort. A photo of the
patient is shown.
Laboratory serum studies show:
TSH
24 µU/mL (N=0.5-5.0)
Thyroxine (T4)
22 µg/dL (N=5-12)
Analysis of the protein hormone will most likely show co- and post-translational modifications of which
of the following amino acids?
A.
Asparagine
B.
Glycine
C.
Histidine
D.
Lysine
E.
Serine
F.
Tyrosine
Concept Approach #3
Goiter
A 37-year-old woman comes to the physician with a 6-month history of neck discomfort. A photo of the
patient is shown.
Laboratory serum studies show:
TSH
24 µU/mL (N=0.5-5.0)
Thyroxine (T4)
22 µg/dL (N=5-12)
Post-translational modifications of the protein hormone will most likely occur in which of the following
cellular locations?
A.
Endoplasmic reticulum
A.
Golgi complex
B.
Lysosome
B.
Lysosome
C.
Mitochondrion
C.
Mitochondrion
D.
Nuclear membrane
D.
Nuclear membrane
E.
Peroxisome
E.
Peroxisome
F.
Plasma membrane
F.
Plasma membrane
Respiratory Acidosis #1
A 64-year-old man is brought to the emergency department complaining of a persistent headache, feeling weak and drowsy,
and having a chronic productive cough. He has been smoking 2 packs of cigarettes a day for over 40 years. A photograph of
the patient is shown.
He is 170 cm (5 ft 7 in) tall and weighs 50 kg (110 lb); BMI is 18 kg/m2. His temperature is 38.3°C (101°F), pulse is 105/min,
respirations are 22/min, and blood pressure is 130/90 mm Hg. Physical examination shows cyanosis, an A-P to lateral ratio of
1:1, use of accessory muscles to inspire, and use of abdominal muscles to expire. Upon ascultation, scattered rhonchi and
wheezes are heard bilaterally. A chest x-ray is shown. Laboratory studies (room air) show:
pH
7.32 (N=7.35-7.45)
PCO2
56 mm Hg (N=33-44)
PO2
35 mm Hg (N=75-105)
HCO3
28 mEq/L (N=22-28)
O2 saturation
60% (N=96-100)
α1-antitrypsin
96 mg/dL (N=110-200)
Based upon the findings, which of the following is the most likely description of the patient’s acid base status?
A.
Acute respiratory acidosis
B.
Acute respiratory alkalosis
C.
Metabolic acidosis with appropriate compensation
D.
Metabolic alkalosis with appropriate compensation
E.
Respiratory acidosis with appropriate compensation
F.
Respiratory alkalosis with appropriate compensation
Respiratory Acidosis #2
A 64-year-old man is brought to the emergency department complaining of a persistent headache, feeling weak and drowsy,
and having a chronic productive cough. He has been smoking 2 packs of cigarettes a day for over 40 years. A photograph of
the patient is shown.
He is 170 cm (5 ft 7 in) tall and weighs 50 kg (110 lb); BMI is 18 kg/m2. His temperature is 38.3°C (101°F), pulse is 105/min,
respirations are 22/min, and blood pressure is 130/90 mm Hg. Physical examination shows cyanosis, an A-P to lateral ratio of
1:1, use of accessory muscles to inspire, and use of abdominal muscles to expire. Upon ascultation, scattered rhonchi and
wheezes are heard bilaterally. A chest x-ray is shown. Laboratory studies (room air) show:
pH
7.32 (N=7.35-7.45)
PCO2
56 mm Hg (N=33-44)
PO2
35 mm Hg (N=75-105)
HCO3
28 mEq/L (N=22-28)
O2 saturation
60% (N=96-100)
α1-antitrypsin
96 mg/dL (N=110-200)
Compensation for the acid base condition in this patient will most likely increase which of the following?
A.
α1-Antitrypsin concentration
B.
Carbonic anhydrase concentration
C.
H+ concentration
D.
HCO3- concentration
E.
PCO2
F.
PO2
Ketogenesis
An investigator is studying the effect of nutrition on pediatric epilepsy. A
matched set of children with a history of epilepsy are provided either a
diet containing 60% medium-chain triglyceride oil, 20% protein, 10%
carbohydrate and 10% other dietary fats or an unrestricted diet. Over the
course of the 12-month study, there is a 20% decrease in the frequency of
seizures in the experimental group of children. An increased serum
concentration of which of the following is most likely in the experimental
group of children?
A. Glucose
B. Insulin
C. Insulin-like growth factor 1
D. Ketone bodies
E. Sorbitol
F. Triglycerides
Iodine Deficiency
An investigator is studying the effect of dietary supplements on endocrine function. Three women from a
remote location in Asia are enrolled as part of the study. A photo of the women is shown.
Laboratory studies show:
TSH
increased
The women are treated with an over-the-counter dietary supplement. During the next 12 months, serum TSH
concentration decreases to the reference range. Which of the following supplements is most likely used to treat
the patients?
A.
Calcium carbonate
B.
Copper histidine
C.
Ferrous gluconate
D.
Magnesium oxide
E.
Potassium iodide
Transcription of Gluconeogenesis Genes
An investigator is studying the effect of nutrition on serum glucose concentrations. After one week of
decreased food intake, serum cortisol concentrations are increased in the experimental group. Transcription of
which of the following hepatic genes shown in the diagram is most likely increased in the experimental group?
A.
B.
C.
D.
E.
F.
A
B
C
D
E
F
Urea Cycle Defects
An investigator is studying the effect of specific defects associated with metabolic pathways. After eating a
protein containing diet, laboratory studies show elevated serum concentrations of arginosuccinate and arginine
but no hyperammonemia in the experimental group. A diagram of the metabolic pathway is shown.
This experimental group most likely has an enzyme deficiency in which of the following marked locations?
A.
A
B.
B
C.
C
D.
D
E.
E
F.
F
Dehydrogenase Complex Subunits
A five-month-old infant is brought to the physician with severe lethargy, poor feeding, and tachypnea. Physical examination shows the
presence of mental, psychomotor, and growth delays. Laboratory studies show increased blood and cerebrospinal fluid lactate and
pyruvate concentrations. Molecular genetic studies show a defect in the riboflavin-dependent E3 component of the pyruvate
dehydrogenase complex. Which of the following additional dehydrogenase-catalyzed steps shown in the diagram is most likely
defective?
A.
B.
C.
D.
E.
F.
G.
A
B
C
D
E
F
G
Ischemic Forearm Test
A 22-year-old man comes to the physician with muscle pain and fatigue. Laboratory studies show compensated hemolytic anemia
with serum lactate and ammonia concentrations within the reference ranges. An ischemic forearm test shows decreased serum
concentrations of lactate and increased serum concentrations of ammonia (N=increased lactate and ammonia). Which of the
following enzyme-catalyzed reaction steps in the diagram shown is most likely deficient in this patient?
A.
B.
C.
D.
E.
F.
A
B
C
D
E
F
Regulation of Glycolysis
When a patient is resting and energy demands are low in skeletal muscles, ATP and citrate bind to and inhibit
which of the following labeled glycolytic enzymes?
A.
B.
C.
D.
E.
A
B
C
D
E
Phototransduction Amplification
Increased enzymatic activity of which of the following labeled locations is most directly
responsible for generating the increased signal amplification associated with
phototransduction?
A.
B.
C.
D.
E.
A
B
C
D
E
Reference Ranges
K+
ClHCO3Ca2+
Urea nitrogen
Glucose, fasting
Creatinine
Phosphorus
Total CO2
Total protein
Albumin
Osmolality
Uric acid
Serum
135-147 mEq/L
3.5-5.0 mEq/L
95-105 mEq/L
22-28 mEq/L
8.4-10.2 mg/dL
7-18 mg/dL
70-110 mg/dL
0.6-1.2 mg/dL
3-4.5 mg/dL
24-30 mEq/L
6-7.8 g/dL
3.5-5.5 g/dL
275-295 mOsm/kg water
3-7 mg/dL
Total cholesterol
LDL
HDL
Triglycerides
Lipids
<200 mg/dL
<130 mg/dL
>40 mg/dL
<160 mg/dL
Na+
Arterial Blood Gases
pH
7.35-7.45
Pa.CO2 (PCO2)
33-44 mm Hg
Pa.O2 (PO2)
75-105 mm Hg
HCO3
22-28 mEq/L
O2 saturation
96-100%
+
Anion gap (no K )
8-16 mEq/L
+
with K
12-20 mEq/L
Bicarbonate gap
-6-+6 mEq/L
Blood
Hemoglobin, male
13-16 g/dL
female
12-15 g/dL
Hematocrit, male
42-50%
female
40-48%
O2 binding capacity
1.34 mL O2/g Hb
Creatinine clearance
Osmolality
Specific gravity
Protein
Urine
90-140 mL/min
50-1400 mOsm/kg water
1.003-1.030
<150 mg/24 h
Questions
• How should important content and concepts should be assessed?
• What is the structure of a clinical or scientific scenario?
• What are examples of effective stems and options/distractors?
• When should images be used in place of descriptions?
• How should laboratory studies be reported?