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COMSAE Phase 1 Form 113 Practice Exam Questions And
Correct Answers (Verified Answers) Plus Rationales
2025|2026 Q&A | Instant Download Pdf
COMSAE Phase 1 Form 113 – Practice Exam
Exam Structure: 176 single-best-answer questions, divided into 4 blocks of 44 questions each.
Block 1: General Principles (Foundational Science & OPP)
1. A 23-year-old man presents with right arm pain after a fall. He cannot extend his wrist. What nerve
is most likely injured?
A. Median
B. Ulnar
C. Radial
D. Axillary
✔✔Answer ✔✔C. Radial
Rationale: The radial nerve innervates the triceps, brachioradialis, and all wrist/finger extensors. Injury
causes “wrist drop” (inability to extend the wrist). An injury to the radial nerve in the spiral groove of the
humerus is a classic complication of a mid-shaft humeral fracture.
2. Which of the following agents inhibits dihydrofolate reductase?
A. Sulfamethoxazole
B. Trimethoprim
C. Ciprofloxacin
D. Rifampin
✔✔Answer ✔✔B. Trimethoprim
Rationale: Trimethoprim selectively inhibits bacterial dihydrofolate reductase (DHFR), blocking the
synthesis of tetrahydrofolate. This is why it is often combined with sulfamethoxazole (which inhibits
dihydropteroate synthase) to create a synergistic effect.
3. A patient with an elevated mean corpuscular volume (MCV) and neurologic symptoms likely has a
deficiency in:
A. Folate
B. Vitamin B12
,2
C. Iron
D. Vitamin C
✔✔Answer ✔✔B. Vitamin B12
Rationale: Both folate and B12 deficiency cause megaloblastic anemia (elevated MCV). However,
neurologic symptoms (e.g., peripheral neuropathy, subacute combined degeneration of the spinal cord)
are unique to B12 deficiency because B12 is required for myelin synthesis. Folate deficiency does not
cause neurologic damage.
4. A positive Trendelenburg sign indicates weakness in which muscle?
A. Vastus lateralis
B. Gluteus medius
C. Gluteus maximus
D. Piriformis
✔✔Answer ✔✔B. Gluteus medius
Rationale: The Trendelenburg sign is a pelvic drop on the contralateral side during single-leg stance. It
indicates weakness of the ipsilateral hip abductors, primarily the gluteus medius and minimus. This is
commonly seen in superior gluteal nerve injury or hip pathology.
5. A 68-year-old woman presents with pain over the lateral elbow. Resisted wrist extension
exacerbates the pain. What is the most likely diagnosis?
A. Medial epicondylitis
B. Lateral epicondylitis
C. Olecranon bursitis
D. Radial head subluxation
✔✔Answer ✔✔B. Lateral epicondylitis
Rationale: Lateral epicondylitis (“tennis elbow”) is caused by overuse of the wrist extensors, especially
the extensor carpi radialis brevis. Pain is reproduced by resisted wrist extension. Medial epicondylitis
(“golfer’s elbow”) causes medial elbow pain with wrist flexion.
6. A positive Lachman test suggests injury to which structure?
A. Posterior cruciate ligament
B. Anterior cruciate ligament
C. Medial collateral ligament
D. Lateral collateral ligament
✔✔Answer ✔✔B. Anterior cruciate ligament
,3
Rationale: The Lachman test is the most sensitive test for ACL injury. It assesses anterior translation of
the tibia relative to the femur at 20-30 degrees of knee flexion. It is more reliable than the anterior
drawer test.
7. Which hormone is increased in 21-hydroxylase deficiency?
A. Aldosterone
B. Cortisol
C. 17-hydroxyprogesterone
D. Dopamine
✔✔Answer ✔✔C. 17-hydroxyprogesterone
Rationale: 21-hydroxylase deficiency is the most common cause of congenital adrenal hyperplasia. The
enzyme defect prevents conversion of 17-hydroxyprogesterone to 11-deoxycortisol, causing
accumulation of 17-OHP and shunting to androgen synthesis. Aldosterone and cortisol are decreased.
8. A 30-year-old woman presents with exophthalmos and heat intolerance. What is the most likely
diagnosis?
A. Hashimoto thyroiditis
B. Subacute thyroiditis
C. Graves disease
D. Toxic nodular goiter
✔✔Answer ✔✔C. Graves disease
Rationale: Graves disease is an autoimmune disorder caused by thyroid-stimulating immunoglobulin
(TSI) that activates the TSH receptor. It presents with hyperthyroidism (heat intolerance, weight loss,
tachycardia) and extrathyroidal manifestations including exophthalmos (proptosis) and pretibial
myxedema.
9. A patient with a history of IV drug use presents with fever, back pain, and a new systolic murmur.
Blood cultures are positive for Staphylococcus aureus. What is the most likely diagnosis?
A. Acute rheumatic fever
B. Infective endocarditis
C. Myocarditis
D. Pericarditis
✔✔Answer ✔✔B. Infective endocarditis
Rationale: S. aureus is a common cause of acute bacterial endocarditis in IV drug users (often affecting
the tricuspid valve). The triad of fever, new or changing murmur, and positive blood cultures is classic.
Echocardiography is used to confirm vegetations.
, 4
10. A patient with cirrhosis develops asterixis and confusion. Which of the following best describes
asterixis?
A. Rapid, rhythmic flexion-extension of the wrist
B. Sudden, non-rhythmic loss of posture (a “liver flap”)
C. Slow, writhing movements of the fingers
D. Irregular, jerky movements of the limbs
✔✔Answer ✔✔B. Sudden, non-rhythmic loss of posture
Rationale: Asterixis (also called “liver flap”) is a negative myoclonus – a sudden, brief loss of muscle tone
that causes the wrist to flap when the patient extends the arms with dorsiflexed wrists. It is a sign of
metabolic encephalopathy, classically seen in hepatic encephalopathy, but also in uremia and
hypercapnia.
Block 2: Organ Systems (Cardio, Pulmonary, Renal)
11. A 60-year-old man with a history of hypertension presents with acute onset of severe “tearing”
chest pain radiating to the back. His blood pressure is 180/100 in the right arm and 100/60 in the left
arm. What is the most likely diagnosis?
A. Acute myocardial infarction
B. Pulmonary embolism
C. Aortic dissection
D. Pericarditis
✔✔Answer ✔✔C. Aortic dissection
Rationale: Aortic dissection (Type A) presents with sudden, severe tearing chest pain that radiates to the
back, often with a pulse differential or blood pressure discrepancy between arms. Hypertension is a
major risk factor.
12. Which of the following ECG findings is most specific for pericarditis?
A. ST-segment elevation in a single lead
B. ST-segment depression in all leads
C. Diffuse, concave (“scooped”) ST-segment elevation with PR-segment depression
D. Pathologic Q waves
✔✔Answer ✔✔C. Diffuse, concave (“scooped”) ST-segment elevation with PR-segment
depression
Rationale: Pericarditis causes diffuse ST-segment elevation (often concave upward) with reciprocal
PR-segment depression. Unlike myocardial infarction, the changes are not limited to a single vascular
territory.
COMSAE Phase 1 Form 113 Practice Exam Questions And
Correct Answers (Verified Answers) Plus Rationales
2025|2026 Q&A | Instant Download Pdf
COMSAE Phase 1 Form 113 – Practice Exam
Exam Structure: 176 single-best-answer questions, divided into 4 blocks of 44 questions each.
Block 1: General Principles (Foundational Science & OPP)
1. A 23-year-old man presents with right arm pain after a fall. He cannot extend his wrist. What nerve
is most likely injured?
A. Median
B. Ulnar
C. Radial
D. Axillary
✔✔Answer ✔✔C. Radial
Rationale: The radial nerve innervates the triceps, brachioradialis, and all wrist/finger extensors. Injury
causes “wrist drop” (inability to extend the wrist). An injury to the radial nerve in the spiral groove of the
humerus is a classic complication of a mid-shaft humeral fracture.
2. Which of the following agents inhibits dihydrofolate reductase?
A. Sulfamethoxazole
B. Trimethoprim
C. Ciprofloxacin
D. Rifampin
✔✔Answer ✔✔B. Trimethoprim
Rationale: Trimethoprim selectively inhibits bacterial dihydrofolate reductase (DHFR), blocking the
synthesis of tetrahydrofolate. This is why it is often combined with sulfamethoxazole (which inhibits
dihydropteroate synthase) to create a synergistic effect.
3. A patient with an elevated mean corpuscular volume (MCV) and neurologic symptoms likely has a
deficiency in:
A. Folate
B. Vitamin B12
,2
C. Iron
D. Vitamin C
✔✔Answer ✔✔B. Vitamin B12
Rationale: Both folate and B12 deficiency cause megaloblastic anemia (elevated MCV). However,
neurologic symptoms (e.g., peripheral neuropathy, subacute combined degeneration of the spinal cord)
are unique to B12 deficiency because B12 is required for myelin synthesis. Folate deficiency does not
cause neurologic damage.
4. A positive Trendelenburg sign indicates weakness in which muscle?
A. Vastus lateralis
B. Gluteus medius
C. Gluteus maximus
D. Piriformis
✔✔Answer ✔✔B. Gluteus medius
Rationale: The Trendelenburg sign is a pelvic drop on the contralateral side during single-leg stance. It
indicates weakness of the ipsilateral hip abductors, primarily the gluteus medius and minimus. This is
commonly seen in superior gluteal nerve injury or hip pathology.
5. A 68-year-old woman presents with pain over the lateral elbow. Resisted wrist extension
exacerbates the pain. What is the most likely diagnosis?
A. Medial epicondylitis
B. Lateral epicondylitis
C. Olecranon bursitis
D. Radial head subluxation
✔✔Answer ✔✔B. Lateral epicondylitis
Rationale: Lateral epicondylitis (“tennis elbow”) is caused by overuse of the wrist extensors, especially
the extensor carpi radialis brevis. Pain is reproduced by resisted wrist extension. Medial epicondylitis
(“golfer’s elbow”) causes medial elbow pain with wrist flexion.
6. A positive Lachman test suggests injury to which structure?
A. Posterior cruciate ligament
B. Anterior cruciate ligament
C. Medial collateral ligament
D. Lateral collateral ligament
✔✔Answer ✔✔B. Anterior cruciate ligament
,3
Rationale: The Lachman test is the most sensitive test for ACL injury. It assesses anterior translation of
the tibia relative to the femur at 20-30 degrees of knee flexion. It is more reliable than the anterior
drawer test.
7. Which hormone is increased in 21-hydroxylase deficiency?
A. Aldosterone
B. Cortisol
C. 17-hydroxyprogesterone
D. Dopamine
✔✔Answer ✔✔C. 17-hydroxyprogesterone
Rationale: 21-hydroxylase deficiency is the most common cause of congenital adrenal hyperplasia. The
enzyme defect prevents conversion of 17-hydroxyprogesterone to 11-deoxycortisol, causing
accumulation of 17-OHP and shunting to androgen synthesis. Aldosterone and cortisol are decreased.
8. A 30-year-old woman presents with exophthalmos and heat intolerance. What is the most likely
diagnosis?
A. Hashimoto thyroiditis
B. Subacute thyroiditis
C. Graves disease
D. Toxic nodular goiter
✔✔Answer ✔✔C. Graves disease
Rationale: Graves disease is an autoimmune disorder caused by thyroid-stimulating immunoglobulin
(TSI) that activates the TSH receptor. It presents with hyperthyroidism (heat intolerance, weight loss,
tachycardia) and extrathyroidal manifestations including exophthalmos (proptosis) and pretibial
myxedema.
9. A patient with a history of IV drug use presents with fever, back pain, and a new systolic murmur.
Blood cultures are positive for Staphylococcus aureus. What is the most likely diagnosis?
A. Acute rheumatic fever
B. Infective endocarditis
C. Myocarditis
D. Pericarditis
✔✔Answer ✔✔B. Infective endocarditis
Rationale: S. aureus is a common cause of acute bacterial endocarditis in IV drug users (often affecting
the tricuspid valve). The triad of fever, new or changing murmur, and positive blood cultures is classic.
Echocardiography is used to confirm vegetations.
, 4
10. A patient with cirrhosis develops asterixis and confusion. Which of the following best describes
asterixis?
A. Rapid, rhythmic flexion-extension of the wrist
B. Sudden, non-rhythmic loss of posture (a “liver flap”)
C. Slow, writhing movements of the fingers
D. Irregular, jerky movements of the limbs
✔✔Answer ✔✔B. Sudden, non-rhythmic loss of posture
Rationale: Asterixis (also called “liver flap”) is a negative myoclonus – a sudden, brief loss of muscle tone
that causes the wrist to flap when the patient extends the arms with dorsiflexed wrists. It is a sign of
metabolic encephalopathy, classically seen in hepatic encephalopathy, but also in uremia and
hypercapnia.
Block 2: Organ Systems (Cardio, Pulmonary, Renal)
11. A 60-year-old man with a history of hypertension presents with acute onset of severe “tearing”
chest pain radiating to the back. His blood pressure is 180/100 in the right arm and 100/60 in the left
arm. What is the most likely diagnosis?
A. Acute myocardial infarction
B. Pulmonary embolism
C. Aortic dissection
D. Pericarditis
✔✔Answer ✔✔C. Aortic dissection
Rationale: Aortic dissection (Type A) presents with sudden, severe tearing chest pain that radiates to the
back, often with a pulse differential or blood pressure discrepancy between arms. Hypertension is a
major risk factor.
12. Which of the following ECG findings is most specific for pericarditis?
A. ST-segment elevation in a single lead
B. ST-segment depression in all leads
C. Diffuse, concave (“scooped”) ST-segment elevation with PR-segment depression
D. Pathologic Q waves
✔✔Answer ✔✔C. Diffuse, concave (“scooped”) ST-segment elevation with PR-segment
depression
Rationale: Pericarditis causes diffuse ST-segment elevation (often concave upward) with reciprocal
PR-segment depression. Unlike myocardial infarction, the changes are not limited to a single vascular
territory.
