Comprehensive Osteopathic Medical
Licensing Examination of the United
States (COMLEX-USA) Level 1 Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2027
Q&A | Instant Download Pdf
Question 1
A 24-year-old man presents with fatigue, muscle weakness, and episodes of
palpitations. Laboratory studies show a serum potassium of 2.8 mEq/L and
metabolic alkalosis. He reports several months of recurrent vomiting. Which
renal abnormality is most likely present?
A. Decreased hydrogen ion secretion
B. Increased bicarbonate excretion
C. Increased renal potassium secretion
D. Decreased aldosterone activity
,Answer: C. Increased renal potassium secretion
Rationale: Persistent vomiting causes volume depletion and metabolic
alkalosis, activating the renin-angiotensin-aldosterone system.
Aldosterone increases distal sodium reabsorption and potassium secretion,
worsening hypokalemia.
Question 2
A newborn develops severe respiratory distress shortly after birth. The
infant has a flattened nose, large tongue, and hypotonia. Which
chromosomal abnormality is most likely?
A. Trisomy 13
B. Trisomy 18
C. Trisomy 21
D. Monosomy X
Answer: C. Trisomy 21
Rationale: Down syndrome is caused most commonly by trisomy 21 and is
associated with hypotonia, characteristic facial features, congenital heart
disease, and developmental delay.
,Question 3
A 7-year-old child develops periorbital edema and frothy urine. Urinalysis
shows heavy proteinuria without hematuria. Electron microscopy
demonstrates diffuse effacement of podocyte foot processes. Which
diagnosis is most likely?
A. Focal segmental glomerulosclerosis
B. Minimal change disease
C. Membranous nephropathy
D. IgA nephropathy
Answer: B. Minimal change disease
Rationale: Minimal change disease is the most common cause of nephrotic
syndrome in children. It is characterized by podocyte foot-process
effacement and usually responds well to corticosteroids.
Question 4
A patient with asthma is prescribed a medication that directly stimulates β2-
adrenergic receptors. Which intracellular change mediates bronchodilation?
A. Decreased cAMP
B. Increased cAMP
, C. Increased IP3
D. Decreased protein kinase A activity
Answer: B. Increased cAMP
Rationale: β2-receptor activation stimulates Gs, increasing adenylyl
cyclase activity and intracellular cAMP. This relaxes bronchial smooth
muscle.
Question 5
A 63-year-old man develops crushing substernal chest pain. ECG shows ST-
segment elevation in leads II, III, and aVF. Which coronary artery is most
likely occluded?
A. Left anterior descending artery
B. Left circumflex artery
C. Right coronary artery
D. Left main coronary artery
Answer: C. Right coronary artery
Rationale: Inferior myocardial infarctions involving leads II, III, and aVF are
most commonly caused by right coronary artery occlusion.
Licensing Examination of the United
States (COMLEX-USA) Level 1 Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2027
Q&A | Instant Download Pdf
Question 1
A 24-year-old man presents with fatigue, muscle weakness, and episodes of
palpitations. Laboratory studies show a serum potassium of 2.8 mEq/L and
metabolic alkalosis. He reports several months of recurrent vomiting. Which
renal abnormality is most likely present?
A. Decreased hydrogen ion secretion
B. Increased bicarbonate excretion
C. Increased renal potassium secretion
D. Decreased aldosterone activity
,Answer: C. Increased renal potassium secretion
Rationale: Persistent vomiting causes volume depletion and metabolic
alkalosis, activating the renin-angiotensin-aldosterone system.
Aldosterone increases distal sodium reabsorption and potassium secretion,
worsening hypokalemia.
Question 2
A newborn develops severe respiratory distress shortly after birth. The
infant has a flattened nose, large tongue, and hypotonia. Which
chromosomal abnormality is most likely?
A. Trisomy 13
B. Trisomy 18
C. Trisomy 21
D. Monosomy X
Answer: C. Trisomy 21
Rationale: Down syndrome is caused most commonly by trisomy 21 and is
associated with hypotonia, characteristic facial features, congenital heart
disease, and developmental delay.
,Question 3
A 7-year-old child develops periorbital edema and frothy urine. Urinalysis
shows heavy proteinuria without hematuria. Electron microscopy
demonstrates diffuse effacement of podocyte foot processes. Which
diagnosis is most likely?
A. Focal segmental glomerulosclerosis
B. Minimal change disease
C. Membranous nephropathy
D. IgA nephropathy
Answer: B. Minimal change disease
Rationale: Minimal change disease is the most common cause of nephrotic
syndrome in children. It is characterized by podocyte foot-process
effacement and usually responds well to corticosteroids.
Question 4
A patient with asthma is prescribed a medication that directly stimulates β2-
adrenergic receptors. Which intracellular change mediates bronchodilation?
A. Decreased cAMP
B. Increased cAMP
, C. Increased IP3
D. Decreased protein kinase A activity
Answer: B. Increased cAMP
Rationale: β2-receptor activation stimulates Gs, increasing adenylyl
cyclase activity and intracellular cAMP. This relaxes bronchial smooth
muscle.
Question 5
A 63-year-old man develops crushing substernal chest pain. ECG shows ST-
segment elevation in leads II, III, and aVF. Which coronary artery is most
likely occluded?
A. Left anterior descending artery
B. Left circumflex artery
C. Right coronary artery
D. Left main coronary artery
Answer: C. Right coronary artery
Rationale: Inferior myocardial infarctions involving leads II, III, and aVF are
most commonly caused by right coronary artery occlusion.
