COMLEX-USA Level 1 Practice Exam
with Verified Questions, Correct
Answers, and Detailed Explanations
for Computer Science
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1. A 25-year-old man presents with fever, chills, and a painful, swollen right
knee. Synovial fluid analysis shows 90,000 WBCs/µL with 85%
neutrophils. Gram stain reveals gram-positive cocci in clusters. Which is
the most likely causative organism?
A) Streptococcus pyogenes
B) Staphylococcus aureus
C) Neisseria gonorrhoeae
D) Escherichia coli
Rationale: The patient’s presentation is consistent with acute septic arthritis.
Gram-positive cocci in clusters indicate Staphylococcus aureus, the most
common cause of septic arthritis in adults.
2. Which of the following best describes the primary mechanism of action
of acetazolamide?
A) Loop diuretic, inhibits Na+/K+/2Cl− symporter
B) Thiazide diuretic, inhibits Na+/Cl− symporter
C) Potassium-sparing diuretic, inhibits ENaC
D) Carbonic anhydrase inhibitor, decreases HCO3− reabsorption
Rationale: Acetazolamide inhibits carbonic anhydrase in the proximal tubule,
leading to decreased bicarbonate reabsorption and mild diuresis.
3. A 3-year-old boy presents with difficulty walking and calf hypertrophy.
Genetic testing reveals a mutation in the dystrophin gene. Which is the
inheritance pattern?
, A) Autosomal dominant
B) X-linked recessive
C) Autosomal recessive
D) Mitochondrial
Rationale: Duchenne muscular dystrophy is caused by mutations in the
dystrophin gene on the X chromosome, showing X-linked recessive inheritance.
4. A patient presents with a painless thyroid nodule. Fine-needle aspiration
shows sheets of cells with "Orphan Annie eye" nuclei. What is the most
likely diagnosis?
A) Follicular carcinoma
B) Medullary carcinoma
C) Papillary thyroid carcinoma
D) Anaplastic carcinoma
Rationale: "Orphan Annie eye" nuclei are characteristic of papillary thyroid
carcinoma, the most common thyroid malignancy.
5. Which vitamin deficiency is associated with megaloblastic anemia and
elevated homocysteine, but normal methylmalonic acid?
A) Vitamin B12
B) Vitamin C
C) Folate (Vitamin B9)
D) Vitamin K
Rationale: Folate deficiency causes megaloblastic anemia with elevated
homocysteine but normal methylmalonic acid levels, distinguishing it from B12
deficiency.
6. A 60-year-old man has progressive difficulty speaking and swallowing.
Neurologic examination shows spasticity, hyperreflexia, and tongue
fasciculations. What is the most likely diagnosis?
A) Myasthenia gravis
B) Multiple sclerosis
C) Amyotrophic lateral sclerosis (ALS)
D) Guillain-Barré syndrome
Rationale: ALS affects both upper and lower motor neurons, leading to
spasticity, hyperreflexia, and muscle fasciculations.
, 7. Which cranial nerve is most commonly affected in Bell’s palsy?
A) CN III
B) CN IV
C) CN VII
D) CN IX
Rationale: Bell’s palsy is caused by inflammation of the facial nerve (CN VII),
resulting in unilateral facial weakness.
8. A 45-year-old woman presents with fatigue, constipation, and cold
intolerance. Laboratory tests reveal elevated TSH and low free T4. What
is the most likely cause?
A) Graves disease
B) Subacute thyroiditis
C) Hashimoto thyroiditis
D) Iodine deficiency
Rationale: Elevated TSH with low free T4 indicates primary hypothyroidism,
most commonly caused by autoimmune Hashimoto thyroiditis.
9. Which of the following is the most common cause of community-
acquired pneumonia in adults?
A) Haemophilus influenzae
B) Streptococcus pneumoniae
C) Mycoplasma pneumoniae
D) Legionella pneumophila
Rationale: Streptococcus pneumoniae is the leading cause of bacterial
community-acquired pneumonia in adults.
10. A 32-year-old woman presents with weight loss, palpitations, and
exophthalmos. Laboratory tests reveal low TSH and high free T4. Which
antibody is most specific for this condition?
A) Anti-TPO antibody
B) Anti-thyroglobulin antibody
C) TSI (Thyroid-stimulating immunoglobulin)
D) Anti-MuSK antibody
Rationale: Graves disease is characterized by autoantibodies (TSI) that
stimulate the TSH receptor, causing hyperthyroidism and ophthalmopathy.
with Verified Questions, Correct
Answers, and Detailed Explanations
for Computer Science
Students||Already Graded A+
1. A 25-year-old man presents with fever, chills, and a painful, swollen right
knee. Synovial fluid analysis shows 90,000 WBCs/µL with 85%
neutrophils. Gram stain reveals gram-positive cocci in clusters. Which is
the most likely causative organism?
A) Streptococcus pyogenes
B) Staphylococcus aureus
C) Neisseria gonorrhoeae
D) Escherichia coli
Rationale: The patient’s presentation is consistent with acute septic arthritis.
Gram-positive cocci in clusters indicate Staphylococcus aureus, the most
common cause of septic arthritis in adults.
2. Which of the following best describes the primary mechanism of action
of acetazolamide?
A) Loop diuretic, inhibits Na+/K+/2Cl− symporter
B) Thiazide diuretic, inhibits Na+/Cl− symporter
C) Potassium-sparing diuretic, inhibits ENaC
D) Carbonic anhydrase inhibitor, decreases HCO3− reabsorption
Rationale: Acetazolamide inhibits carbonic anhydrase in the proximal tubule,
leading to decreased bicarbonate reabsorption and mild diuresis.
3. A 3-year-old boy presents with difficulty walking and calf hypertrophy.
Genetic testing reveals a mutation in the dystrophin gene. Which is the
inheritance pattern?
, A) Autosomal dominant
B) X-linked recessive
C) Autosomal recessive
D) Mitochondrial
Rationale: Duchenne muscular dystrophy is caused by mutations in the
dystrophin gene on the X chromosome, showing X-linked recessive inheritance.
4. A patient presents with a painless thyroid nodule. Fine-needle aspiration
shows sheets of cells with "Orphan Annie eye" nuclei. What is the most
likely diagnosis?
A) Follicular carcinoma
B) Medullary carcinoma
C) Papillary thyroid carcinoma
D) Anaplastic carcinoma
Rationale: "Orphan Annie eye" nuclei are characteristic of papillary thyroid
carcinoma, the most common thyroid malignancy.
5. Which vitamin deficiency is associated with megaloblastic anemia and
elevated homocysteine, but normal methylmalonic acid?
A) Vitamin B12
B) Vitamin C
C) Folate (Vitamin B9)
D) Vitamin K
Rationale: Folate deficiency causes megaloblastic anemia with elevated
homocysteine but normal methylmalonic acid levels, distinguishing it from B12
deficiency.
6. A 60-year-old man has progressive difficulty speaking and swallowing.
Neurologic examination shows spasticity, hyperreflexia, and tongue
fasciculations. What is the most likely diagnosis?
A) Myasthenia gravis
B) Multiple sclerosis
C) Amyotrophic lateral sclerosis (ALS)
D) Guillain-Barré syndrome
Rationale: ALS affects both upper and lower motor neurons, leading to
spasticity, hyperreflexia, and muscle fasciculations.
, 7. Which cranial nerve is most commonly affected in Bell’s palsy?
A) CN III
B) CN IV
C) CN VII
D) CN IX
Rationale: Bell’s palsy is caused by inflammation of the facial nerve (CN VII),
resulting in unilateral facial weakness.
8. A 45-year-old woman presents with fatigue, constipation, and cold
intolerance. Laboratory tests reveal elevated TSH and low free T4. What
is the most likely cause?
A) Graves disease
B) Subacute thyroiditis
C) Hashimoto thyroiditis
D) Iodine deficiency
Rationale: Elevated TSH with low free T4 indicates primary hypothyroidism,
most commonly caused by autoimmune Hashimoto thyroiditis.
9. Which of the following is the most common cause of community-
acquired pneumonia in adults?
A) Haemophilus influenzae
B) Streptococcus pneumoniae
C) Mycoplasma pneumoniae
D) Legionella pneumophila
Rationale: Streptococcus pneumoniae is the leading cause of bacterial
community-acquired pneumonia in adults.
10. A 32-year-old woman presents with weight loss, palpitations, and
exophthalmos. Laboratory tests reveal low TSH and high free T4. Which
antibody is most specific for this condition?
A) Anti-TPO antibody
B) Anti-thyroglobulin antibody
C) TSI (Thyroid-stimulating immunoglobulin)
D) Anti-MuSK antibody
Rationale: Graves disease is characterized by autoantibodies (TSI) that
stimulate the TSH receptor, causing hyperthyroidism and ophthalmopathy.
