|COMLEX-USA Level 1 Preparation 150 Questions |
Verified Answers with Rationales | Graded A+
Academic Year: 2025/2026
SECTION 1: FOUNDATIONAL SCIENCES & CLINICAL MEDICINE
Questions 1–25
Question 1
A 2-day-old neonate presents with poor feeding, vomiting, and "maple syrup" smelling urine. A
deficiency in the branched-chain alpha-keto acid dehydrogenase complex is suspected. Which
of the following amino acids is most likely to be elevated in this patient's serum?
A) Phenylalanine
B) Tyrosine
C) Leucine
D) Methionine
Correct answer: C
Rationale: Maple Syrup Urine Disease (MSUD) is caused by a deficiency in the enzyme
complex that breaks down branched-chain amino acids: Isoleucine, Leucine, and Valine (I Love
Vermont). Leucine elevation is particularly neurotoxic in these infants.
Question 2
A 65-year-old male with a history of COPD presents with fever and a cough productive of
"rust-colored" sputum. A Gram stain of the sputum reveals Gram-positive, lancet-shaped
diplococci. Which of the following is the most likely pathogen?
A) Staphylococcus aureus
,B) Streptococcus pneumoniae
C) Klebsiella pneumoniae
D) Mycoplasma pneumoniae
Correct answer: B
Rationale: Streptococcus pneumoniae is the most common cause of community-acquired
pneumonia. The classic clinical "buzzword" is rust-colored sputum, and the classic microscopic
finding is Gram-positive, lancet-shaped diplococci.
Question 3
A 55-year-old male is being treated for chronic open-angle glaucoma. He is prescribed a
medication that acts as a non-selective beta-adrenergic antagonist to decrease aqueous humor
production. Which of the following is a potential contraindication for this medication?
A) Hypertension
B) Hyperthyroidism
C) Asthma
D) Glaucoma
Correct answer: C
Rationale: Timolol is a non-selective beta-blocker used topically for glaucoma. Because it blocks
Beta-2 receptors in the lungs as well as Beta-1 in the heart, it can cause bronchoconstriction
and is generally contraindicated in patients with asthma or severe COPD.
Question 4
A 45-year-old male presents with chronic low back pain. Physical examination reveals a short
left leg (apparent), a left posterior superior iliac spine (PSIS) that is superior compared to the
right, and a left anterior inferior iliac spine (AIIS) that is inferior compared to the right. What is
the most likely sacral diagnosis?
A) Left-on-left torsion
B) Right-on-right torsion
C) Left unilateral flexion
D) Right unilateral flexion
Correct answer: A
, Rationale: In a sacral torsion, the side of the axis (oblique axis) is named first, and the side of
the rotation is named second. The findings (deep sulcus on the right, shallow on the left; inferior
lateral angle (ILA) posterior on the left) indicate the sacrum is rotated around a left oblique axis.
A left-on-left torsion means the axis is on the left and the base (superior aspect) is rotated
anteriorly on the left.
Question 5
A 58-year-old male with hypertension and type 2 diabetes presents with substernal chest
pressure radiating to the jaw, occurring at rest and lasting 15 minutes. ECG shows ST-segment
depression in leads V3–V6. Troponin I is elevated. Which of the following is the most
appropriate next step?
A) Aspirin and discharge with outpatient stress test
B) Oral nitroglycerin and beta-blocker at home
C) Immediate percutaneous coronary intervention (PCI)
D) Intravenous thrombolytics
E) Coronary artery bypass grafting (CABG) within 48 hours
Correct answer: C
Rationale: The patient presents with non-ST-elevation myocardial infarction (NSTEMI) with
elevated troponin and ongoing symptoms. High-risk NSTEMI warrants early invasive strategy
with PCI within 24 hours. Thrombolytics are not indicated for NSTEMI. CABG is not first-line for
acute management.
Question 6
A 64-year-old man presents with crushing substernal chest pain radiating to his left arm. ECG
shows ST-segment elevations in leads II, III, and aVF. Which artery is most likely occluded?
A) Left anterior descending
B) Left circumflex
C) Right coronary artery
D) Posterior descending artery
E) Left main coronary
Correct answer: C
Rationale: Inferior MI (ST elevations in leads II, III, and aVF) usually results from right coronary
artery (RCA) occlusion. LAD causes anterior MI (V1-V4).