COMLEX-USA Level 1 Examination Questions
With Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant Download Pdf
1. A 24-year-old presents with fever, productive cough, and right
lower lobe consolidation on chest X-ray. Which organism is the
most likely cause of community-acquired pneumonia in an
otherwise healthy adult?
A) Klebsiella pneumoniae
B) Streptococcus pneumoniae
C) Pseudomonas aeruginosa
D) Mycoplasma pneumoniae
Answer: B
Rationale: Streptococcus pneumoniae is the most common cause of
community-acquired pneumonia in healthy adults and typically
presents with lobar consolidation, fever, and productive cough.
2. Which heart sound is associated with increased left ventricular
filling pressure and decreased compliance?
,A) S1
B) S2
C) S3
D) S4
Answer: D
Rationale: S4 occurs just before S1 due to atrial contraction against a
stiff ventricle, commonly seen in LV hypertrophy or ischemia.
3. A patient has hypercalcemia, bone pain, and “punched-out”
lesions on skull X-ray. What is the most likely diagnosis?
A) Osteoporosis
B) Multiple myeloma
C) Osteomalacia
D) Metastatic prostate cancer
Answer: B
Rationale: Multiple myeloma causes malignant plasma cell
proliferation leading to lytic bone lesions, hypercalcemia, and anemia.
4. Which vitamin deficiency causes night blindness?
,A) Vitamin A
B) Vitamin D
C) Vitamin E
D) Vitamin K
Answer: A
Rationale: Vitamin A is required for rhodopsin formation in retinal
rods, essential for low-light vision.
5. A 60-year-old smoker presents with painless hematuria. Which
malignancy is most likely?
A) Renal cell carcinoma
B) Bladder transitional cell carcinoma
C) Prostate adenocarcinoma
D) Wilms tumor
Answer: B
Rationale: Transitional cell carcinoma of the bladder is strongly
associated with smoking and presents with painless hematuria.
6. Which structure is primarily responsible for production of
cerebrospinal fluid?
, A) Arachnoid villi
B) Choroid plexus
C) Dural venous sinus
D) Ependymal cells only
Answer: B
Rationale: The choroid plexus produces CSF within the ventricles of the
brain.
7. What is the mechanism of action of beta-blockers in
hypertension?
A) Vasodilation via nitric oxide
B) Decreased renin release from JG cells
C) Increased sodium excretion
D) Calcium channel blockade
Answer: B
Rationale: Beta-1 blockade reduces renin release, decreasing RAAS
activation and blood pressure.
8. Which organism causes peptic ulcers associated with urease
production?
With Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant Download Pdf
1. A 24-year-old presents with fever, productive cough, and right
lower lobe consolidation on chest X-ray. Which organism is the
most likely cause of community-acquired pneumonia in an
otherwise healthy adult?
A) Klebsiella pneumoniae
B) Streptococcus pneumoniae
C) Pseudomonas aeruginosa
D) Mycoplasma pneumoniae
Answer: B
Rationale: Streptococcus pneumoniae is the most common cause of
community-acquired pneumonia in healthy adults and typically
presents with lobar consolidation, fever, and productive cough.
2. Which heart sound is associated with increased left ventricular
filling pressure and decreased compliance?
,A) S1
B) S2
C) S3
D) S4
Answer: D
Rationale: S4 occurs just before S1 due to atrial contraction against a
stiff ventricle, commonly seen in LV hypertrophy or ischemia.
3. A patient has hypercalcemia, bone pain, and “punched-out”
lesions on skull X-ray. What is the most likely diagnosis?
A) Osteoporosis
B) Multiple myeloma
C) Osteomalacia
D) Metastatic prostate cancer
Answer: B
Rationale: Multiple myeloma causes malignant plasma cell
proliferation leading to lytic bone lesions, hypercalcemia, and anemia.
4. Which vitamin deficiency causes night blindness?
,A) Vitamin A
B) Vitamin D
C) Vitamin E
D) Vitamin K
Answer: A
Rationale: Vitamin A is required for rhodopsin formation in retinal
rods, essential for low-light vision.
5. A 60-year-old smoker presents with painless hematuria. Which
malignancy is most likely?
A) Renal cell carcinoma
B) Bladder transitional cell carcinoma
C) Prostate adenocarcinoma
D) Wilms tumor
Answer: B
Rationale: Transitional cell carcinoma of the bladder is strongly
associated with smoking and presents with painless hematuria.
6. Which structure is primarily responsible for production of
cerebrospinal fluid?
, A) Arachnoid villi
B) Choroid plexus
C) Dural venous sinus
D) Ependymal cells only
Answer: B
Rationale: The choroid plexus produces CSF within the ventricles of the
brain.
7. What is the mechanism of action of beta-blockers in
hypertension?
A) Vasodilation via nitric oxide
B) Decreased renin release from JG cells
C) Increased sodium excretion
D) Calcium channel blockade
Answer: B
Rationale: Beta-1 blockade reduces renin release, decreasing RAAS
activation and blood pressure.
8. Which organism causes peptic ulcers associated with urease
production?
