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COMSAE PHASE 1 PROFESSIONAL EXAM – FORM 114 Questions
with Detailed Rationales UPDATED
Updated 2026/2027 Edition
Total Questions: 176
Sections: 4 × 44 Questions
Time Allowed: 4 hours
SECTION 1 (Questions 1–44)
Question 1
A 45-year-old man presents with fever, chills, and a productive
cough. Chest X-ray shows lobar consolidation. Which of the
following is the most likely causative organism?
A. Mycoplasma pneumoniae
B. Streptococcus pneumoniae
C. Legionella pneumophila
D. Klebsiella pneumoniae
E. Pseudomonas aeruginosa
Answer: B
Rationale: Lobar consolidation in a community-acquired
pneumonia is most commonly caused by Streptococcus
pneumoniae. Mycoplasma and Legionella typically present with
atypical pneumonia patterns.
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Question 2
Which of the following is the rate-limiting enzyme of the
pentose phosphate pathway?
A. Glucose-6-phosphate dehydrogenase
B. Transketolase
C. 6-phosphogluconate dehydrogenase
D. Ribose-5-phosphate isomerase
E. Phosphofructokinase-1
Answer: A
Rationale: G6PD is the rate-limiting enzyme of the pentose
phosphate pathway, producing NADPH and ribose-5-phosphate.
PFK-1 is rate-limiting for glycolysis.
Question 3
A 55-year-old woman presents with fatigue, weight gain, and
cold intolerance. TSH is elevated, free T4 is low. Which of the
following is the most likely autoantibody present?
A. Anti-TSH receptor stimulating antibody
B. Anti-thyroid peroxidase antibody
C. Anti-thyroglobulin antibody only
D. Anti-adrenal antibody
E. Anti-islet cell antibody
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Answer: B
Rationale: Primary hypothyroidism with elevated TSH and low
T4 is most commonly Hashimoto thyroiditis, associated with
anti-thyroid peroxidase (TPO) antibodies. Anti-TSH receptor
stimulating is Graves.
Question 4
A 30-year-old man with a history of intravenous drug use
presents with a new heart murmur, fever, and splinter
hemorrhages. Blood cultures grow Staphylococcus aureus.
What is the most likely diagnosis?
A. Rheumatic fever
B. Infective endocarditis
C. Pericarditis
D. Myocarditis
E. Atrial myxoma
Answer: B
Rationale: Fever, new murmur, and positive blood cultures with
S. aureus in an IV drug user suggest infective endocarditis.
Question 5
Which of the following is the primary mechanism of action of
methotrexate?
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A. Inhibits dihydrofolate reductase
B. Inhibits thymidylate synthase
C. Inhibits ribonucleotide reductase
D. Inhibits topoisomerase II
E. Inhibits microtubule polymerization
Answer: A
Rationale: Methotrexate inhibits dihydrofolate reductase,
reducing tetrahydrofolate and nucleotide synthesis.
Question 6
A 65-year-old man presents with sudden onset of severe chest
pain, diaphoresis, and ST elevation in leads II, III, and aVF.
Which coronary artery is most likely occluded?
A. Left anterior descending
B. Left circumflex
C. Right coronary artery
D. Left main
E. Posterior descending artery
Answer: C
Rationale: ST elevation in inferior leads (II, III, aVF) indicates
inferior MI, usually due to right coronary artery occlusion.
Question 7
COMSAE PHASE 1 PROFESSIONAL EXAM – FORM 114 Questions
with Detailed Rationales UPDATED
Updated 2026/2027 Edition
Total Questions: 176
Sections: 4 × 44 Questions
Time Allowed: 4 hours
SECTION 1 (Questions 1–44)
Question 1
A 45-year-old man presents with fever, chills, and a productive
cough. Chest X-ray shows lobar consolidation. Which of the
following is the most likely causative organism?
A. Mycoplasma pneumoniae
B. Streptococcus pneumoniae
C. Legionella pneumophila
D. Klebsiella pneumoniae
E. Pseudomonas aeruginosa
Answer: B
Rationale: Lobar consolidation in a community-acquired
pneumonia is most commonly caused by Streptococcus
pneumoniae. Mycoplasma and Legionella typically present with
atypical pneumonia patterns.
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Question 2
Which of the following is the rate-limiting enzyme of the
pentose phosphate pathway?
A. Glucose-6-phosphate dehydrogenase
B. Transketolase
C. 6-phosphogluconate dehydrogenase
D. Ribose-5-phosphate isomerase
E. Phosphofructokinase-1
Answer: A
Rationale: G6PD is the rate-limiting enzyme of the pentose
phosphate pathway, producing NADPH and ribose-5-phosphate.
PFK-1 is rate-limiting for glycolysis.
Question 3
A 55-year-old woman presents with fatigue, weight gain, and
cold intolerance. TSH is elevated, free T4 is low. Which of the
following is the most likely autoantibody present?
A. Anti-TSH receptor stimulating antibody
B. Anti-thyroid peroxidase antibody
C. Anti-thyroglobulin antibody only
D. Anti-adrenal antibody
E. Anti-islet cell antibody
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Answer: B
Rationale: Primary hypothyroidism with elevated TSH and low
T4 is most commonly Hashimoto thyroiditis, associated with
anti-thyroid peroxidase (TPO) antibodies. Anti-TSH receptor
stimulating is Graves.
Question 4
A 30-year-old man with a history of intravenous drug use
presents with a new heart murmur, fever, and splinter
hemorrhages. Blood cultures grow Staphylococcus aureus.
What is the most likely diagnosis?
A. Rheumatic fever
B. Infective endocarditis
C. Pericarditis
D. Myocarditis
E. Atrial myxoma
Answer: B
Rationale: Fever, new murmur, and positive blood cultures with
S. aureus in an IV drug user suggest infective endocarditis.
Question 5
Which of the following is the primary mechanism of action of
methotrexate?
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A. Inhibits dihydrofolate reductase
B. Inhibits thymidylate synthase
C. Inhibits ribonucleotide reductase
D. Inhibits topoisomerase II
E. Inhibits microtubule polymerization
Answer: A
Rationale: Methotrexate inhibits dihydrofolate reductase,
reducing tetrahydrofolate and nucleotide synthesis.
Question 6
A 65-year-old man presents with sudden onset of severe chest
pain, diaphoresis, and ST elevation in leads II, III, and aVF.
Which coronary artery is most likely occluded?
A. Left anterior descending
B. Left circumflex
C. Right coronary artery
D. Left main
E. Posterior descending artery
Answer: C
Rationale: ST elevation in inferior leads (II, III, aVF) indicates
inferior MI, usually due to right coronary artery occlusion.
Question 7
