COMSAE Form ASA 113
Comprehensive Osteopathic Medical
Practice Exam Questions, Verified
Answers, and In-Depth Rationales
(2026 Edition)
1. A 67-year-old man presents with resting tremor,
bradykinesia, and rigidity. Which neurotransmitter
deficiency is primarily responsible for his condition?
A. Acetylcholine
B. Serotonin
C. Dopamine
D. GABA
Answer: C. Dopamine
Rationale: Parkinson disease results from degeneration of
dopaminergic neurons in the substantia nigra pars
compacta. The resulting dopamine deficiency in the basal
ganglia causes resting tremor, rigidity, bradykinesia, and
postural instability.
2. A patient develops fever, hypotension, and diffuse
erythematous rash after prolonged tampon use. Which
organism is the most likely cause?
,A. Streptococcus pneumoniae
B. Staphylococcus aureus
C. Neisseria gonorrhoeae
D. Escherichia coli
Answer: B. Staphylococcus aureus
Rationale: Toxic shock syndrome is classically caused by
toxin-producing Staphylococcus aureus. Toxic shock
syndrome toxin-1 acts as a superantigen, causing massive
cytokine release, fever, hypotension, and rash.
3. A newborn has a machine-like continuous murmur.
Which congenital cardiac defect is most likely?
A. Ventricular septal defect
B. Tetralogy of Fallot
C. Patent ductus arteriosus
D. Atrial septal defect
Answer: C. Patent ductus arteriosus
Rationale: Patent ductus arteriosus produces a
characteristic continuous “machine-like” murmur due to
persistent blood flow from the aorta to the pulmonary
artery throughout systole and diastole.
4. Which cranial nerve mediates the afferent limb of the
corneal reflex?
A. CN III
B. CN V1
,C. CN VII
D. CN X
Answer: B. CN V1
Rationale: The ophthalmic division of the trigeminal nerve
(V1) detects corneal stimulation. The facial nerve (CN VII)
provides the efferent limb by closing the eyelids.
5. A 25-year-old woman presents with exophthalmos, heat
intolerance, and weight loss. What is the most likely
diagnosis?
A. Hashimoto thyroiditis
B. Graves disease
C. Subacute thyroiditis
D. Toxic multinodular goiter
Answer: B. Graves disease
Rationale: Graves disease is an autoimmune disorder
caused by thyroid-stimulating immunoglobulins activating
TSH receptors. Exophthalmos and pretibial myxedema are
characteristic findings.
6. Which electrolyte abnormality is most commonly
associated with peaked T waves on ECG?
A. Hypokalemia
B. Hypercalcemia
C. Hyperkalemia
D. Hypocalcemia
, Answer: C. Hyperkalemia
Rationale: Elevated serum potassium accelerates ventricular
repolarization, producing peaked T waves. Severe
hyperkalemia may progress to widened QRS complexes and
cardiac arrest.
7. A patient has microcytic anemia and elevated total iron-
binding capacity. Which diagnosis is most likely?
A. Iron deficiency anemia
B. Anemia of chronic disease
C. Sideroblastic anemia
D. Thalassemia
Answer: A. Iron deficiency anemia
Rationale: Iron deficiency anemia is characterized by low
ferritin, low serum iron, elevated TIBC, and microcytosis.
Increased TIBC reflects increased transferrin production by
the liver.
8. Which portion of the nephron is primarily responsible
for water reabsorption under the influence of ADH?
A. Proximal tubule
B. Thick ascending limb
C. Distal convoluted tubule
D. Collecting duct
Answer: D. Collecting duct
Comprehensive Osteopathic Medical
Practice Exam Questions, Verified
Answers, and In-Depth Rationales
(2026 Edition)
1. A 67-year-old man presents with resting tremor,
bradykinesia, and rigidity. Which neurotransmitter
deficiency is primarily responsible for his condition?
A. Acetylcholine
B. Serotonin
C. Dopamine
D. GABA
Answer: C. Dopamine
Rationale: Parkinson disease results from degeneration of
dopaminergic neurons in the substantia nigra pars
compacta. The resulting dopamine deficiency in the basal
ganglia causes resting tremor, rigidity, bradykinesia, and
postural instability.
2. A patient develops fever, hypotension, and diffuse
erythematous rash after prolonged tampon use. Which
organism is the most likely cause?
,A. Streptococcus pneumoniae
B. Staphylococcus aureus
C. Neisseria gonorrhoeae
D. Escherichia coli
Answer: B. Staphylococcus aureus
Rationale: Toxic shock syndrome is classically caused by
toxin-producing Staphylococcus aureus. Toxic shock
syndrome toxin-1 acts as a superantigen, causing massive
cytokine release, fever, hypotension, and rash.
3. A newborn has a machine-like continuous murmur.
Which congenital cardiac defect is most likely?
A. Ventricular septal defect
B. Tetralogy of Fallot
C. Patent ductus arteriosus
D. Atrial septal defect
Answer: C. Patent ductus arteriosus
Rationale: Patent ductus arteriosus produces a
characteristic continuous “machine-like” murmur due to
persistent blood flow from the aorta to the pulmonary
artery throughout systole and diastole.
4. Which cranial nerve mediates the afferent limb of the
corneal reflex?
A. CN III
B. CN V1
,C. CN VII
D. CN X
Answer: B. CN V1
Rationale: The ophthalmic division of the trigeminal nerve
(V1) detects corneal stimulation. The facial nerve (CN VII)
provides the efferent limb by closing the eyelids.
5. A 25-year-old woman presents with exophthalmos, heat
intolerance, and weight loss. What is the most likely
diagnosis?
A. Hashimoto thyroiditis
B. Graves disease
C. Subacute thyroiditis
D. Toxic multinodular goiter
Answer: B. Graves disease
Rationale: Graves disease is an autoimmune disorder
caused by thyroid-stimulating immunoglobulins activating
TSH receptors. Exophthalmos and pretibial myxedema are
characteristic findings.
6. Which electrolyte abnormality is most commonly
associated with peaked T waves on ECG?
A. Hypokalemia
B. Hypercalcemia
C. Hyperkalemia
D. Hypocalcemia
, Answer: C. Hyperkalemia
Rationale: Elevated serum potassium accelerates ventricular
repolarization, producing peaked T waves. Severe
hyperkalemia may progress to widened QRS complexes and
cardiac arrest.
7. A patient has microcytic anemia and elevated total iron-
binding capacity. Which diagnosis is most likely?
A. Iron deficiency anemia
B. Anemia of chronic disease
C. Sideroblastic anemia
D. Thalassemia
Answer: A. Iron deficiency anemia
Rationale: Iron deficiency anemia is characterized by low
ferritin, low serum iron, elevated TIBC, and microcytosis.
Increased TIBC reflects increased transferrin production by
the liver.
8. Which portion of the nephron is primarily responsible
for water reabsorption under the influence of ADH?
A. Proximal tubule
B. Thick ascending limb
C. Distal convoluted tubule
D. Collecting duct
Answer: D. Collecting duct
