NBME Comprehensive Basic Science Test
In a steady state, the difference in CO2 content between the venous blood leaving a tissue and the arterial blood entering the tissue is determined by which of the following ratios?
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A 16-month-old boy is brought to the physician by his mother for a well-child examination. His mother expresses concern that he did not walk until the age of 14 months, whereas his older sister walked at the age of 10 months. Physical examination shows no abnormalities. Which of the following best explains this patient’s condition?
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A 77-year-old woman is visited by the home care nurse who notes that the patient is more lethargic than usual. Her skin and mucous membranes are dry. An increase in the serum concentration or activity of which of the following provides the strongest indication that the patient is dehydrated?
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A male newborn delivered at 26 weeks’ gestation develops respiratory distress immediately after a spontaneous vaginal delivery. His respirations are 40/min. Physical examination shows cyanosis and lower rib retractions with respiration. Heart sounds are normal. Bilateral breath sounds are heard on auscultation. A chest x-ray shows bilateral lung opacities. The most likely cause of this patient’s breathing difficulties is insufficient production of which of the following substances?
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A 28-year-old woman, gravida 1, para 1, comes to the physician because of progressive fatigue since delivering a male newborn 6 months ago. She is sleeping 8 to 10 hours nightly, but she is still tired during the day. She also has not had a menstrual period since her pregnancy. Pregnancy was complicated during the third trimester by severe bleeding from placenta previa. She required multiple blood transfusions during the cesarean delivery, but she did well after the delivery. She was unable to breast-feed her newborn because of poor milk production. Which of the following is the most likely diagnosis?
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A 12-year-old African American boy is brought to the physician by his mother because of a swollen right earlobe for 3 weeks. He had the ear pierced at a local mall 6 weeks ago. The swelling has persisted despite removal of the earring 3 weeks ago. The mother developed a thick rubbery scar on her abdomen after a cesarean delivery 12 years ago. His temperature is 37°C (98.6°F). Physical examination shows a nontender, flesh-colored swelling of the right earlobe. The skin is intact over the swelling, and it is soft and nontender. There is no cervical lymphadenopathy. Which of the following is the most likely cause of the swelling in this patient?
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A 5-year-old boy is brought to the physician by his parents because of an 8-month history of difficulty walking. His parents say that he limps when he walks and has a waddling gait; he also has difficulty standing. When getting up from a sitting position, he uses his hands to walk up his thighs and push his body into a standing position. His parents have not noticed any weakness of his arms. His mother is an only child, but she has an uncle who became bedridden as a child and died of respiratory arrest. Physical examination shows prominent calf muscles. Muscle strength is 4/5 at both hips but normal elsewhere. This patient most likely has a mutation in the gene coding for which of the following proteins?
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A 27-year-old man comes to the physician because of pain with urination for 3 days. He has had no fever or chills. He is sexually active with three partners and does not use condoms consistently. He began having sexual relations with his most recent partner 1 week ago. His temperature is 37°C (98.6°F). Physical examination shows no abnormalities except for a clear, watery urethral discharge. Urinalysis shows 10–20 WBC/hpf but no bacteria. Which of the following is the most likely causal organism?
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A 20-year-old college student develops fever, severe pharyngitis, hepatosplenomegaly, and lymphadenopathy. The pathogenesis of this syndrome most likely involves a double-stranded DNA virus infection of which of the following cells?
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A 2-year-old boy with Down syndrome is brought to the physician by his mother for a follow-up examination. His blood pressure is increased in the upper extremities and decreased in the lower extremities. Physical examination shows cyanosis of the lower extremities. An AP x-ray of the chest shows notching of the inferior surfaces of the 3rd through 8th ribs. The diagnosis of left ventricular hypertrophy is suspected. Which of the following is the most likely underlying abnormality in this patient?
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A 1-day-old neonate has hemolytic disease of the newborn. The parents are both Rh-positive, but IgG isohemagglutinins are found in the mother’s blood. Which of the following parental blood types is most likely to cause this condition?
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A previously healthy 42-year-old woman comes to the emergency department because of progressive shortness of breath and intermittent cough productive of blood-tinged sputum for 10 days. She has no history of major medical illness and takes no medications. Her respirations are 24/min. Diffuse rhonchi are heard in both lung fields on auscultation. A chest x-ray shows patchy opacities bilaterally. Laboratory studies show: Serum creatinine 2.5 mg/dL Urine Protein 3+ RBC 3+ RBC casts numerous A serum anti-glomerular basement membrane autoantibody assay is positive. Which of the following is the most likely diagnosis?
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A 10-year-old boy is found to have mild iron deficiency anemia. His mother informs the physician that the family members belong to a religious denomination that does not consume meat. Her son refuses to eat dark green vegetables or to take vitamin pills, stating that they make him feel nauseated. It is most appropriate for the physician to ask the mother which of the following questions next?
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A 64-year-old man comes to the physician because of a 3-day history of painful rash over his right flank. Three days before the rash appeared, he had pain in the same area. His temperature is 37.4°C (99.3°F), pulse is 78/min, respirations are 17/min, and blood pressure is 130/70 mm Hg. Physical examination shows clustered lesions in a band-like area over the right flank. The lesions have an erythematous base and are crusted. Which of the following is the most likely causal virus?
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A 27-year-old man with AIDS is brought to the hospital 30 minutes after having a seizure. He currently takes no medications. A CT scan of the head shows multiple ring-enhancing lesions. Which of the following is the most likely diagnosis?
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An investigator has conducted an experiment to determine whether certain environmental exposure morbidity is eliminated if a person carries a specific allele of three different genes on three separate chromosomes. The frequencies of an individual having the allele for these respective genes are 0.6, 0.2, and 0.1. All three alleles are necessary to confer protection. The probability that a randomly selected individual will have all three alleles is closest to which of the following?
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A health inspector confiscates chickens smuggled into Taiwan from mainland China after she discovers them in the hold of a ship. Testing shows that, although the chickens appear healthy, they are infected with the H5N1 subtype of the influenza A virus. Which of the following is the primary concern for human health from these virus-infected chickens?
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A 35-year-old woman has hypertension and truncal obesity. Serum studies show: Cortisol (AM) 100 µg/dL (N=5–20) Cortisol (PM) 100 µg/dL (N=2.5–10) ACTH (AM) 100 µg/dL (N=20–100) Cortisol 8 h after 1 mg dexamethasone 95 µg/dL Cortisol 8 h after 8 mg dexamethasone 30 µg/dL (N=5–20) Which of the following is the most likely cause of this woman’s increased serum cortisol concentration?
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A 42-year-old woman comes to the physician for a routine health maintenance examination. She says that she feels fine. She is 170 cm (5 ft 7 in) tall and weighs 86 kg (190 lb); BMI is 30 kg/m2 . Her blood pressure is 131/82 mm Hg. Physical examination shows no other abnormalities. Fasting serum studies show: Glucose 105 mg/dL Cholesterol, total 210 mg/dL Triglycerides 185 mg/dL C-reactive protein 0.35 mg/L (N=20–100) This patient is at increased risk for developing which of the following conditions?
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