NBME CBSE (USMLE STEP 1) EXAM
COMPREHENSIVE TEST BANK - 300 QUESTIONS
WITH ANSWERS AND RATIONALES National Board of
Medical Examiners | 2026-2027 Edition | Most Recent
Edition
EXAM OVERVIEW
The National Board of Medical Examiners (NBME) Comprehensive Basic Science
Examination (CBSE) assesses a medical student's understanding of and ability to apply
important concepts of the sciences basic to the practice of medicine, with special
emphasis on principles and mechanisms underlying health, disease, and modes of
therapy . The CBSE is a comprehensive basic science examination that serves as a
predictor of performance on the USMLE Step 1 .
The USMLE Step 1 is a one-day examination. For exams administered on or after May 14,
2026, the test delivery software will feature an updated interface with 14 blocks of 30
minutes each, containing up to 20 questions per block, for a total of up to 280 items
across an 8-hour testing session . Examinees can only review items within the current
block and are unable to return to previous blocks once closed .
This comprehensive test bank covers all major content areas including general principles
of pathology, pharmacology, microbiology, immunology, biochemistry, genetics, organ
system disorders, biostatistics, and behavioral sciences .
SECTION 1: CARDIOVASCULAR SYSTEM (Questions 1-50)
1. A 68-year-old woman with type 2 diabetes and hypertension that has been poorly
controlled despite hydrochlorothiazide treatment presents with BP 150/96 mmHg. Labs
show serum glucose 130 mg/dL and proteinuria. In addition to current therapy, which is
the most appropriate pharmacotherapy?
A) Metoprolol
B) Lisinopril
,C) Amlodipine
D) Doxazosin
Answer: B) Lisinopril
Rationale: Lisinopril is an ACE inhibitor that is preferred in patients with diabetes and
proteinuria. ACE inhibitors reduce intraglomerular pressure and slow the progression of
diabetic nephropathy by decreasing efferent arteriolar resistance. They also provide
cardiovascular protection and are first-line therapy for hypertension in patients with
diabetes and proteinuria .
2. A patient with heart failure presents with JVP elevation that rises during inspiration.
What is this finding called?
A) Pulsus paradoxus
B) Kussmaul sign
C) Corrigan's pulse
D) Waterhammer pulse
Answer: B) Kussmaul sign
Rationale: Kussmaul sign is characterized by a rise in JVP during inspiration, which is
paradoxical and indicates impaired right ventricular filling. This is classic for constrictive
pericarditis but can also be seen in severe right heart failure and restrictive
cardiomyopathy. It contrasts with the normal decrease in JVP during inspiration .
3. In the evaluation of pulmonary embolism, a sudden onset of shortness of breath with
calf swelling in a patient who is hypoxemic would most likely demonstrate which finding?
A) Respiratory acidosis
B) Respiratory alkalosis with metabolic compensation
C) Normal blood gases
D) Metabolic acidosis
Answer: B) Respiratory alkalosis with metabolic compensation
Rationale: Pulmonary embolism causes hypoxemia, which stimulates hyperventilation
leading to respiratory alkalosis. Over 2 days, metabolic compensation occurs as the
kidneys excrete bicarbonate. This pattern of respiratory alkalosis with metabolic
compensation is characteristic of acute PE .
,4. A patient with pulmonary arterial hypertension would most likely demonstrate which
finding?
A) P2 softer than A2
B) P2 louder than A2
C) S3 gallop
D) Systolic ejection murmur
Answer: B) P2 louder than A2
Rationale: Pulmonary arterial hypertension (PAH) is characterized by increased
pulmonary artery pressure, which causes the pulmonic valve closure (P2) to become
louder than the aortic valve closure (A2). PAH is associated with BMPR2 mutations, high
endothelin, and low nitric oxide, leading to smooth muscle hypertrophy, fibrosis, and
narrowing of the pulmonary arterioles .
5. A patient with pulmonary arterial hypertension is being treated with an endothelin
receptor antagonist. Which medication is an example of this class?
A) Sildenafil
B) Bosentan
C) Epoprostenol
D) Nitroglycerin
Answer: B) Bosentan
Rationale: Bosentan and Ambrisentan are endothelin receptor antagonists used to treat
pulmonary arterial hypertension. Sildenafil works by increasing cGMP
(phosphodiesterase-5 inhibitor), while epoprostenol is a prostacyclin analog. Endothelin
receptor antagonists block the vasoconstrictive effects of endothelin-1 .
6. A 70-year-old man undergoing evaluation for occult blood in the stool dies in a motor
vehicle collision. A photograph of the transverse colon is shown. What is the most likely
diagnosis?
A) Adenocarcinoma
B) Tubular adenoma
, C) Hyperplastic polyp
D) Villous adenoma
Answer: B) Tubular adenoma
Rationale: Tubular adenomas are the most common type of colonic polyp and are
precursors to colorectal adenocarcinoma. They are characterized by tubular architecture
on histology. The presence of occult blood in the stool, along with the gross appearance
of a polyp in the colon, suggests a tubular adenoma .
7. A 38-year-old man with a 1-week history of watery, itchy eyes and a runny nose is
diagnosed with allergic rhinitis. Physical examination shows inflamed nasal mucosa but
no congestion in the lower lung. What is the most appropriate pharmacotherapy?
A) Diphenhydramine
B) Loratadine
C) Fluticasone
D) Montelukast
Answer: B) Loratadine
Rationale: Loratadine is a second-generation antihistamine that is preferred for allergic
rhinitis because it is non-sedating and has fewer anticholinergic side effects compared to
first-generation antihistamines like diphenhydramine. It is effective for symptoms of
watery, itchy eyes and runny nose .
8. A patient is diagnosed with hereditary spherocytosis. Which finding would most likely
be seen on the peripheral blood smear?
A) Target cells
B) Spherocytes
C) Schistocytes
D) Sickle cells
Answer: B) Spherocytes
Rationale: Hereditary spherocytosis is characterized by spherocytes on peripheral blood
smear due to defects in membrane proteins (ankyrin, spectrin). The spleen selectively
destroys these abnormal cells, leading to anemia, jaundice, and splenomegaly.
COMPREHENSIVE TEST BANK - 300 QUESTIONS
WITH ANSWERS AND RATIONALES National Board of
Medical Examiners | 2026-2027 Edition | Most Recent
Edition
EXAM OVERVIEW
The National Board of Medical Examiners (NBME) Comprehensive Basic Science
Examination (CBSE) assesses a medical student's understanding of and ability to apply
important concepts of the sciences basic to the practice of medicine, with special
emphasis on principles and mechanisms underlying health, disease, and modes of
therapy . The CBSE is a comprehensive basic science examination that serves as a
predictor of performance on the USMLE Step 1 .
The USMLE Step 1 is a one-day examination. For exams administered on or after May 14,
2026, the test delivery software will feature an updated interface with 14 blocks of 30
minutes each, containing up to 20 questions per block, for a total of up to 280 items
across an 8-hour testing session . Examinees can only review items within the current
block and are unable to return to previous blocks once closed .
This comprehensive test bank covers all major content areas including general principles
of pathology, pharmacology, microbiology, immunology, biochemistry, genetics, organ
system disorders, biostatistics, and behavioral sciences .
SECTION 1: CARDIOVASCULAR SYSTEM (Questions 1-50)
1. A 68-year-old woman with type 2 diabetes and hypertension that has been poorly
controlled despite hydrochlorothiazide treatment presents with BP 150/96 mmHg. Labs
show serum glucose 130 mg/dL and proteinuria. In addition to current therapy, which is
the most appropriate pharmacotherapy?
A) Metoprolol
B) Lisinopril
,C) Amlodipine
D) Doxazosin
Answer: B) Lisinopril
Rationale: Lisinopril is an ACE inhibitor that is preferred in patients with diabetes and
proteinuria. ACE inhibitors reduce intraglomerular pressure and slow the progression of
diabetic nephropathy by decreasing efferent arteriolar resistance. They also provide
cardiovascular protection and are first-line therapy for hypertension in patients with
diabetes and proteinuria .
2. A patient with heart failure presents with JVP elevation that rises during inspiration.
What is this finding called?
A) Pulsus paradoxus
B) Kussmaul sign
C) Corrigan's pulse
D) Waterhammer pulse
Answer: B) Kussmaul sign
Rationale: Kussmaul sign is characterized by a rise in JVP during inspiration, which is
paradoxical and indicates impaired right ventricular filling. This is classic for constrictive
pericarditis but can also be seen in severe right heart failure and restrictive
cardiomyopathy. It contrasts with the normal decrease in JVP during inspiration .
3. In the evaluation of pulmonary embolism, a sudden onset of shortness of breath with
calf swelling in a patient who is hypoxemic would most likely demonstrate which finding?
A) Respiratory acidosis
B) Respiratory alkalosis with metabolic compensation
C) Normal blood gases
D) Metabolic acidosis
Answer: B) Respiratory alkalosis with metabolic compensation
Rationale: Pulmonary embolism causes hypoxemia, which stimulates hyperventilation
leading to respiratory alkalosis. Over 2 days, metabolic compensation occurs as the
kidneys excrete bicarbonate. This pattern of respiratory alkalosis with metabolic
compensation is characteristic of acute PE .
,4. A patient with pulmonary arterial hypertension would most likely demonstrate which
finding?
A) P2 softer than A2
B) P2 louder than A2
C) S3 gallop
D) Systolic ejection murmur
Answer: B) P2 louder than A2
Rationale: Pulmonary arterial hypertension (PAH) is characterized by increased
pulmonary artery pressure, which causes the pulmonic valve closure (P2) to become
louder than the aortic valve closure (A2). PAH is associated with BMPR2 mutations, high
endothelin, and low nitric oxide, leading to smooth muscle hypertrophy, fibrosis, and
narrowing of the pulmonary arterioles .
5. A patient with pulmonary arterial hypertension is being treated with an endothelin
receptor antagonist. Which medication is an example of this class?
A) Sildenafil
B) Bosentan
C) Epoprostenol
D) Nitroglycerin
Answer: B) Bosentan
Rationale: Bosentan and Ambrisentan are endothelin receptor antagonists used to treat
pulmonary arterial hypertension. Sildenafil works by increasing cGMP
(phosphodiesterase-5 inhibitor), while epoprostenol is a prostacyclin analog. Endothelin
receptor antagonists block the vasoconstrictive effects of endothelin-1 .
6. A 70-year-old man undergoing evaluation for occult blood in the stool dies in a motor
vehicle collision. A photograph of the transverse colon is shown. What is the most likely
diagnosis?
A) Adenocarcinoma
B) Tubular adenoma
, C) Hyperplastic polyp
D) Villous adenoma
Answer: B) Tubular adenoma
Rationale: Tubular adenomas are the most common type of colonic polyp and are
precursors to colorectal adenocarcinoma. They are characterized by tubular architecture
on histology. The presence of occult blood in the stool, along with the gross appearance
of a polyp in the colon, suggests a tubular adenoma .
7. A 38-year-old man with a 1-week history of watery, itchy eyes and a runny nose is
diagnosed with allergic rhinitis. Physical examination shows inflamed nasal mucosa but
no congestion in the lower lung. What is the most appropriate pharmacotherapy?
A) Diphenhydramine
B) Loratadine
C) Fluticasone
D) Montelukast
Answer: B) Loratadine
Rationale: Loratadine is a second-generation antihistamine that is preferred for allergic
rhinitis because it is non-sedating and has fewer anticholinergic side effects compared to
first-generation antihistamines like diphenhydramine. It is effective for symptoms of
watery, itchy eyes and runny nose .
8. A patient is diagnosed with hereditary spherocytosis. Which finding would most likely
be seen on the peripheral blood smear?
A) Target cells
B) Spherocytes
C) Schistocytes
D) Sickle cells
Answer: B) Spherocytes
Rationale: Hereditary spherocytosis is characterized by spherocytes on peripheral blood
smear due to defects in membrane proteins (ankyrin, spectrin). The spleen selectively
destroys these abnormal cells, leading to anemia, jaundice, and splenomegaly.
