2026 VERSION COMSAE Phase 1 Clinical
Science Practice Exam Questions with
Verified Answers and Detailed Rationales
Question 1
A 64-year-old man with a 50-pack-year smoking history
presents with progressive dyspnea, chronic productive cough,
and weight loss. Pulmonary function testing shows an
FEV₁/FVC ratio of 0.55. His arterial blood gas analysis reveals
chronic respiratory acidosis with metabolic compensation.
Which of the following best explains the mechanism
responsible for his increased pulmonary vascular resistance?
A. Destruction of pulmonary capillaries due to pulmonary
fibrosis
B. Increased pulmonary venous pressure caused by left
ventricular failure
C. Hypoxic pulmonary vasoconstriction caused by chronic
alveolar hypoxia
D. Increased pulmonary blood flow due to a left-to-right
shunt
Chronic hypoxemia causes pulmonary arteriolar
vasoconstriction, which increases pulmonary vascular
resistance and may eventually produce pulmonary
hypertension and right-sided heart failure (cor pulmonale).
This is a major complication of advanced COPD.
,Question 2
A 23-year-old woman presents with fatigue, weight loss, heat
intolerance, and palpitations. Examination reveals a diffusely
enlarged thyroid and bilateral exophthalmos. Laboratory
studies show elevated free T₄ and suppressed TSH. Which
mechanism most directly explains her thyroid disease?
A. Destruction of thyroid follicles by cytotoxic T cells
B. Autoantibody stimulation of the TSH receptor
C. Inhibition of thyroid peroxidase by circulating antibodies
D. Autonomous secretion of TSH by a pituitary adenoma
Graves disease results from IgG autoantibodies that bind and
stimulate the TSH receptor. The resulting increase in thyroid
hormone synthesis causes suppression of pituitary TSH
through negative feedback.
Question 3
A 45-year-old man develops severe epigastric pain radiating
to the back after heavy alcohol consumption. Serum lipase is
markedly elevated. Several days later, he develops
hypocalcemia. Which mechanism best explains this
electrolyte abnormality?
A. Increased renal calcium excretion
B. Reduced parathyroid hormone secretion
C. Saponification of calcium by fatty acids released during
pancreatic fat necrosis
,D. Increased calcitonin secretion caused by pancreatic
inflammation
Acute pancreatitis can cause fat necrosis. Free fatty acids
released from damaged adipocytes bind calcium, producing
insoluble calcium soaps through saponification and lowering
serum calcium.
Question 4
A 31-year-old woman develops sudden unilateral weakness
and aphasia. She has a history of recurrent migraines with
aura but no vascular risk factors. Imaging reveals an ischemic
stroke. Further evaluation shows a patent foramen ovale.
Which mechanism most likely caused her stroke?
A. Atherosclerotic plaque rupture
B. Thrombus formation within the left ventricle
C. Paradoxical embolism through a right-to-left intracardiac
shunt
D. Cerebral vasospasm caused by migraine
Venous thrombi can cross a patent foramen ovale when right-
sided pressure exceeds left-sided pressure, allowing a
paradoxical embolus to enter systemic circulation and occlude
a cerebral artery.
Question 5
A 67-year-old man with atrial fibrillation develops sudden
severe abdominal pain that appears disproportionate to his
, benign abdominal examination. Serum lactate is elevated.
Which artery is most likely occluded?
A. Inferior mesenteric artery
B. Celiac artery
C. Superior mesenteric artery
D. Renal artery
Acute mesenteric ischemia caused by embolization from atrial
fibrillation most commonly involves the superior mesenteric
artery. The classic presentation is severe abdominal pain out
of proportion to physical findings.
Question 6
A 19-year-old college student presents with fever, headache,
neck stiffness, and photophobia. Cerebrospinal fluid
demonstrates neutrophilic pleocytosis, elevated protein, and
decreased glucose. Gram stain shows gram-negative
diplococci. Which bacterial component is primarily
responsible for the severe inflammatory response?
A. M protein
B. Pneumolysin
C. Lipooligosaccharide endotoxin
D. Protein A
Neisseria meningitidis contains lipooligosaccharide, an
endotoxin that triggers intense cytokine release and can
cause septic shock, disseminated intravascular coagulation,
and Waterhouse-Friderichsen syndrome.
Science Practice Exam Questions with
Verified Answers and Detailed Rationales
Question 1
A 64-year-old man with a 50-pack-year smoking history
presents with progressive dyspnea, chronic productive cough,
and weight loss. Pulmonary function testing shows an
FEV₁/FVC ratio of 0.55. His arterial blood gas analysis reveals
chronic respiratory acidosis with metabolic compensation.
Which of the following best explains the mechanism
responsible for his increased pulmonary vascular resistance?
A. Destruction of pulmonary capillaries due to pulmonary
fibrosis
B. Increased pulmonary venous pressure caused by left
ventricular failure
C. Hypoxic pulmonary vasoconstriction caused by chronic
alveolar hypoxia
D. Increased pulmonary blood flow due to a left-to-right
shunt
Chronic hypoxemia causes pulmonary arteriolar
vasoconstriction, which increases pulmonary vascular
resistance and may eventually produce pulmonary
hypertension and right-sided heart failure (cor pulmonale).
This is a major complication of advanced COPD.
,Question 2
A 23-year-old woman presents with fatigue, weight loss, heat
intolerance, and palpitations. Examination reveals a diffusely
enlarged thyroid and bilateral exophthalmos. Laboratory
studies show elevated free T₄ and suppressed TSH. Which
mechanism most directly explains her thyroid disease?
A. Destruction of thyroid follicles by cytotoxic T cells
B. Autoantibody stimulation of the TSH receptor
C. Inhibition of thyroid peroxidase by circulating antibodies
D. Autonomous secretion of TSH by a pituitary adenoma
Graves disease results from IgG autoantibodies that bind and
stimulate the TSH receptor. The resulting increase in thyroid
hormone synthesis causes suppression of pituitary TSH
through negative feedback.
Question 3
A 45-year-old man develops severe epigastric pain radiating
to the back after heavy alcohol consumption. Serum lipase is
markedly elevated. Several days later, he develops
hypocalcemia. Which mechanism best explains this
electrolyte abnormality?
A. Increased renal calcium excretion
B. Reduced parathyroid hormone secretion
C. Saponification of calcium by fatty acids released during
pancreatic fat necrosis
,D. Increased calcitonin secretion caused by pancreatic
inflammation
Acute pancreatitis can cause fat necrosis. Free fatty acids
released from damaged adipocytes bind calcium, producing
insoluble calcium soaps through saponification and lowering
serum calcium.
Question 4
A 31-year-old woman develops sudden unilateral weakness
and aphasia. She has a history of recurrent migraines with
aura but no vascular risk factors. Imaging reveals an ischemic
stroke. Further evaluation shows a patent foramen ovale.
Which mechanism most likely caused her stroke?
A. Atherosclerotic plaque rupture
B. Thrombus formation within the left ventricle
C. Paradoxical embolism through a right-to-left intracardiac
shunt
D. Cerebral vasospasm caused by migraine
Venous thrombi can cross a patent foramen ovale when right-
sided pressure exceeds left-sided pressure, allowing a
paradoxical embolus to enter systemic circulation and occlude
a cerebral artery.
Question 5
A 67-year-old man with atrial fibrillation develops sudden
severe abdominal pain that appears disproportionate to his
, benign abdominal examination. Serum lactate is elevated.
Which artery is most likely occluded?
A. Inferior mesenteric artery
B. Celiac artery
C. Superior mesenteric artery
D. Renal artery
Acute mesenteric ischemia caused by embolization from atrial
fibrillation most commonly involves the superior mesenteric
artery. The classic presentation is severe abdominal pain out
of proportion to physical findings.
Question 6
A 19-year-old college student presents with fever, headache,
neck stiffness, and photophobia. Cerebrospinal fluid
demonstrates neutrophilic pleocytosis, elevated protein, and
decreased glucose. Gram stain shows gram-negative
diplococci. Which bacterial component is primarily
responsible for the severe inflammatory response?
A. M protein
B. Pneumolysin
C. Lipooligosaccharide endotoxin
D. Protein A
Neisseria meningitidis contains lipooligosaccharide, an
endotoxin that triggers intense cytokine release and can
cause septic shock, disseminated intravascular coagulation,
and Waterhouse-Friderichsen syndrome.
