COMSAE Level 1 — Form C Practice Exam
QUESTIONS AND CORRECT ANSWERS
(VERIFIED ANSWERS) PLUS RATIONALES 2026
Q&A | INSTANT DOWNLOAD PDF
1. A 6-year-old boy presents with ear pain and fever.
Otoscopic exam shows a bulging tympanic membrane with
loss of landmarks. The most likely organism is:
A. Streptococcus pyogenes
B. Streptococcus pneumoniae
C. Pseudomonas aeruginosa
D. Mycoplasma pneumoniae
Rationale: Streptococcus pneumoniae is the most
common cause of acute otitis media in children due to its
colonization of the nasopharynx and virulence factors
promoting middle ear infection.
2. A patient with diabetic ketoacidosis has an anion gap of 22
mEq/L. Which contributes to the elevated anion gap?
A. Hyperchloremia
B. Hypoalbuminemia
C. Accumulation of ketone bodies (beta-hydroxybutyrate,
acetoacetate)
D. Metabolic alkalosis
Rationale: In DKA, increased ketone bodies (unmeasured
anions) raise the anion gap metabolic acidosis.
,3. A 45-year-old with sudden severe chest pain radiating to
the back — worst pain of life. Suspect aortic dissection.
Best initial diagnostic test in a hemodynamically stable
patient:
A. Plain chest X-ray
B. CT angiography of chest
C. Transthoracic echocardiogram
D. Ventilation-perfusion scan
Rationale: CT angiography provides rapid, high-sensitivity
imaging for aortic dissection in stable patients.
4. Which enzyme deficiency causes phenylketonuria (PKU)?
A. Homogentisate oxidase
B. Phenylalanine hydroxylase
C. Tyrosinase
D. Branched-chain alpha-keto dehydrogenase
Rationale: PKU is due to phenylalanine hydroxylase
deficiency, preventing conversion of phenylalanine to
tyrosine.
5. A 60-year-old male smoker has a chronic productive cough
for 3 months each year for 2 consecutive years. The best
diagnosis is:
A. Asthma
B. Bronchiectasis
C. Chronic bronchitis
D. Emphysema
Rationale: Chronic productive cough for ≥3 months in ≥2
, consecutive years defines chronic bronchitis, a COPD
subtype.
6. A patient on warfarin has an elevated INR. Which vitamin
deficiency potentiates warfarin’s effect?
A. Vitamin C
B. Vitamin D
C. Vitamin K deficiency
D. Vitamin A
Rationale: Warfarin inhibits vitamin K-dependent clotting
factor activation; low vitamin K potentiates
anticoagulation and raises INR.
7. Best initial management for anaphylaxis in the ED:
A. Intravenous hydrocortisone
B. Intramuscular epinephrine
C. H1 antihistamine IV
D. Albuterol inhaler
Rationale: IM epinephrine is the first-line, life-saving
treatment for anaphylaxis to reverse bronchospasm,
hypotension, and mucosal edema.
8. The PR interval represents:
A. Ventricular depolarization
B. Atrial repolarization
C. AV nodal conduction time (beginning of atrial
depolarization to beginning of ventricular depolarization)
D. Ventricular repolarization
Rationale: PR interval measures conduction from the
, onset of atrial depolarization (P wave) to ventricular
depolarization (QRS).
9. A 25-year-old female with fever, malar rash, joint pain:
autoantibodies likely to be positive:
A. Anti-centromere
B. Anti-dsDNA
C. Anti-mitochondrial
D. Anti-thyroid peroxidase
Rationale: Systemic lupus erythematosus commonly
features anti-dsDNA antibodies which correlate with
disease activity.
10. A 40-year-old presents with microcytic anemia. Most
useful initial test to differentiate iron deficiency from
thalassemia trait:
A. Serum folate
B. Serum B12
C. Mentzer index (MCV/RBC) or RBC count/Ferritin —
actual best is ferritin
D. Reticulocyte count
Rationale: Ferritin is the best single test for iron
deficiency; Mentzer index helps screen (low suggests
thalassemia trait).
11. The mechanism of action of loop diuretics (e.g.,
furosemide):
A. Block ENaC in collecting duct
B. Inhibit carbonic anhydrase
QUESTIONS AND CORRECT ANSWERS
(VERIFIED ANSWERS) PLUS RATIONALES 2026
Q&A | INSTANT DOWNLOAD PDF
1. A 6-year-old boy presents with ear pain and fever.
Otoscopic exam shows a bulging tympanic membrane with
loss of landmarks. The most likely organism is:
A. Streptococcus pyogenes
B. Streptococcus pneumoniae
C. Pseudomonas aeruginosa
D. Mycoplasma pneumoniae
Rationale: Streptococcus pneumoniae is the most
common cause of acute otitis media in children due to its
colonization of the nasopharynx and virulence factors
promoting middle ear infection.
2. A patient with diabetic ketoacidosis has an anion gap of 22
mEq/L. Which contributes to the elevated anion gap?
A. Hyperchloremia
B. Hypoalbuminemia
C. Accumulation of ketone bodies (beta-hydroxybutyrate,
acetoacetate)
D. Metabolic alkalosis
Rationale: In DKA, increased ketone bodies (unmeasured
anions) raise the anion gap metabolic acidosis.
,3. A 45-year-old with sudden severe chest pain radiating to
the back — worst pain of life. Suspect aortic dissection.
Best initial diagnostic test in a hemodynamically stable
patient:
A. Plain chest X-ray
B. CT angiography of chest
C. Transthoracic echocardiogram
D. Ventilation-perfusion scan
Rationale: CT angiography provides rapid, high-sensitivity
imaging for aortic dissection in stable patients.
4. Which enzyme deficiency causes phenylketonuria (PKU)?
A. Homogentisate oxidase
B. Phenylalanine hydroxylase
C. Tyrosinase
D. Branched-chain alpha-keto dehydrogenase
Rationale: PKU is due to phenylalanine hydroxylase
deficiency, preventing conversion of phenylalanine to
tyrosine.
5. A 60-year-old male smoker has a chronic productive cough
for 3 months each year for 2 consecutive years. The best
diagnosis is:
A. Asthma
B. Bronchiectasis
C. Chronic bronchitis
D. Emphysema
Rationale: Chronic productive cough for ≥3 months in ≥2
, consecutive years defines chronic bronchitis, a COPD
subtype.
6. A patient on warfarin has an elevated INR. Which vitamin
deficiency potentiates warfarin’s effect?
A. Vitamin C
B. Vitamin D
C. Vitamin K deficiency
D. Vitamin A
Rationale: Warfarin inhibits vitamin K-dependent clotting
factor activation; low vitamin K potentiates
anticoagulation and raises INR.
7. Best initial management for anaphylaxis in the ED:
A. Intravenous hydrocortisone
B. Intramuscular epinephrine
C. H1 antihistamine IV
D. Albuterol inhaler
Rationale: IM epinephrine is the first-line, life-saving
treatment for anaphylaxis to reverse bronchospasm,
hypotension, and mucosal edema.
8. The PR interval represents:
A. Ventricular depolarization
B. Atrial repolarization
C. AV nodal conduction time (beginning of atrial
depolarization to beginning of ventricular depolarization)
D. Ventricular repolarization
Rationale: PR interval measures conduction from the
, onset of atrial depolarization (P wave) to ventricular
depolarization (QRS).
9. A 25-year-old female with fever, malar rash, joint pain:
autoantibodies likely to be positive:
A. Anti-centromere
B. Anti-dsDNA
C. Anti-mitochondrial
D. Anti-thyroid peroxidase
Rationale: Systemic lupus erythematosus commonly
features anti-dsDNA antibodies which correlate with
disease activity.
10. A 40-year-old presents with microcytic anemia. Most
useful initial test to differentiate iron deficiency from
thalassemia trait:
A. Serum folate
B. Serum B12
C. Mentzer index (MCV/RBC) or RBC count/Ferritin —
actual best is ferritin
D. Reticulocyte count
Rationale: Ferritin is the best single test for iron
deficiency; Mentzer index helps screen (low suggests
thalassemia trait).
11. The mechanism of action of loop diuretics (e.g.,
furosemide):
A. Block ENaC in collecting duct
B. Inhibit carbonic anhydrase
