NBME CBSE / USMLE Step 1
200-Question Comprehensive Practice Examination
Four Multiple-Choice Options | Correct Answers Italicized
2027/2028
Questions 1–50
1. A 23-year-old man with severe diarrhea develops weakness. Laboratory studies show a
serum potassium concentration of 2.8 mEq/L. Which renal mechanism most directly
contributes to potassium conservation during hypokalemia?
A. Increased potassium secretion by principal cells
B. Decreased potassium reabsorption in the proximal tubule
C. Increased potassium reabsorption by α-intercalated cells
D. Increased sodium delivery to the collecting duct
Answer: C
2. A patient with chronic kidney disease develops metabolic acidosis. Which renal response
normally increases during metabolic acidosis?
A. Bicarbonate excretion
B. Hydrogen ion secretion
,C. Ammonium excretion decrease
D. Phosphate excretion decrease
Answer: B
3. A 67-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
B. Left circumflex
C. Right coronary
D. Left main coronary
Answer: C
4. A newborn has cyanosis that does not significantly improve with supplemental oxygen.
Echocardiography demonstrates transposition of the great arteries. Which fetal structure is
essential for survival until corrective treatment?
A. Ductus venosus
B. Foramen ovale
C. Ligamentum arteriosum
D. Umbilical artery
Answer: B
5. A 34-year-old woman has fatigue, weight gain, constipation, and cold intolerance. TSH is
elevated and free T4 is decreased. Which antibody is most likely present?
,A. Anti-dsDNA
B. Anti-thyroid peroxidase
C. Anti-centromere
D. Anti-mitochondrial
Answer: B
6. A patient with pernicious anemia develops neurologic abnormalities and macrocytosis.
Which metabolite is expected to be elevated?
A. Homocysteine only
B. Methylmalonic acid
C. Uric acid only
D. Bilirubin only
Answer: B
7. A child with recurrent bacterial infections has absent tonsils and very low levels of all
immunoglobulin classes. Which condition is most likely?
A. DiGeorge syndrome
B. X-linked agammaglobulinemia
C. Chronic granulomatous disease
D. Selective IgA deficiency
Answer: B
8. A patient develops flushing, diarrhea, wheezing, and hypotension after receiving a
medication. Which mediator is primarily responsible for the immediate hypersensitivity
response?
, A. Histamine
B. IL-2
C. Interferon-γ
D. C3b
Answer: A
9. A man with hypertension is started on lisinopril. Several weeks later, he develops
persistent dry cough. Increased accumulation of which substance contributes to this
adverse effect?
A. Angiotensin II
B. Aldosterone
C. Bradykinin
D. Renin
Answer: C
10. A patient taking warfarin develops excessive anticoagulation. Which laboratory test is
most appropriate for monitoring this medication?
A. aPTT
B. PT/INR
C. Bleeding time
D. Thrombin time
Answer: B
200-Question Comprehensive Practice Examination
Four Multiple-Choice Options | Correct Answers Italicized
2027/2028
Questions 1–50
1. A 23-year-old man with severe diarrhea develops weakness. Laboratory studies show a
serum potassium concentration of 2.8 mEq/L. Which renal mechanism most directly
contributes to potassium conservation during hypokalemia?
A. Increased potassium secretion by principal cells
B. Decreased potassium reabsorption in the proximal tubule
C. Increased potassium reabsorption by α-intercalated cells
D. Increased sodium delivery to the collecting duct
Answer: C
2. A patient with chronic kidney disease develops metabolic acidosis. Which renal response
normally increases during metabolic acidosis?
A. Bicarbonate excretion
B. Hydrogen ion secretion
,C. Ammonium excretion decrease
D. Phosphate excretion decrease
Answer: B
3. A 67-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
B. Left circumflex
C. Right coronary
D. Left main coronary
Answer: C
4. A newborn has cyanosis that does not significantly improve with supplemental oxygen.
Echocardiography demonstrates transposition of the great arteries. Which fetal structure is
essential for survival until corrective treatment?
A. Ductus venosus
B. Foramen ovale
C. Ligamentum arteriosum
D. Umbilical artery
Answer: B
5. A 34-year-old woman has fatigue, weight gain, constipation, and cold intolerance. TSH is
elevated and free T4 is decreased. Which antibody is most likely present?
,A. Anti-dsDNA
B. Anti-thyroid peroxidase
C. Anti-centromere
D. Anti-mitochondrial
Answer: B
6. A patient with pernicious anemia develops neurologic abnormalities and macrocytosis.
Which metabolite is expected to be elevated?
A. Homocysteine only
B. Methylmalonic acid
C. Uric acid only
D. Bilirubin only
Answer: B
7. A child with recurrent bacterial infections has absent tonsils and very low levels of all
immunoglobulin classes. Which condition is most likely?
A. DiGeorge syndrome
B. X-linked agammaglobulinemia
C. Chronic granulomatous disease
D. Selective IgA deficiency
Answer: B
8. A patient develops flushing, diarrhea, wheezing, and hypotension after receiving a
medication. Which mediator is primarily responsible for the immediate hypersensitivity
response?
, A. Histamine
B. IL-2
C. Interferon-γ
D. C3b
Answer: A
9. A man with hypertension is started on lisinopril. Several weeks later, he develops
persistent dry cough. Increased accumulation of which substance contributes to this
adverse effect?
A. Angiotensin II
B. Aldosterone
C. Bradykinin
D. Renin
Answer: C
10. A patient taking warfarin develops excessive anticoagulation. Which laboratory test is
most appropriate for monitoring this medication?
A. aPTT
B. PT/INR
C. Bleeding time
D. Thrombin time
Answer: B
