Practice Test 3 - USMLE Step 1
20 questions. Answer them in any order, then submit to see your score and every explanation.
- What is the most likely immediate effect of oligomycin on oxygen consumption and the strength of the proton motive force?
- The addition of fludrocortisone is intended to replace the activity of which of the following deficient hormones?
- A basic science laboratory wishes to use excess fetal tissue obtained after clinically indicated elective terminations for developing stem-cell therapies. The investigators have no role in patient care or decision-making regarding termination. In addition to Institutional Review Board approval, which of the following regulatory elements is required to ensure ethical compliance in the United States?
- Which of the following is the most probable fate for this self-reactive B cell?
- Which statistical test is most appropriate to determine if there is a significant difference in the mean IOP between the medication and placebo groups?
- Which study design provides the strongest evidence for a cause-and-effect relationship between an intervention and an outcome?
- This is because hepatocytes lack which of the following enzymes?
- A full-thickness rectal biopsy performed to confirm the suspected diagnosis would most likely show a complete absence of which of the following structures in the affected segment?
- This deficiency leads to unregulated production of bradykinin due to the uncontrolled activity of which enzyme?
- The researcher is suggesting that the study may have resulted in which type of error due to insufficient power?
- Which of the following is a key mechanism contributing to the maintenance of immune privilege in these sites?
- Which of the following molecules derived from triglyceride breakdown can be used as a substrate for hepatic gluconeogenesis?
- Researchers conduct a case-control study of 300 adults aged 40–70 to test whether long-term proton pump inhibitor (PPI) use is associated with chronic kidney disease (CKD). Cases are 150 patients with newly diagnosed CKD (eGFR <60 for ≥3 months) identified from nephrology clinics. Controls are 150 patients from the same clinics with eGFR ≥90, frequency-matched on age and sex. Prior PPI exposure is obtained from electronic prescription records for the preceding 5 years. Results: 78/150 (52%) cases had ≥1 year of PPI prescriptions vs 54/150 (36%) controls. Investigators note that people referred to nephrology may differ from the general population. Which of the following best represents the outcome of this study?
- Which of the following best describes the distribution of BMI in this population?
- A 25-year-old man develops anaphylaxis minutes after IV contrast; he had a similar reaction previously and now has elevated tryptase. Which of the following best describes the mechanism of the patient's symptoms?
- The development of this malignancy is most strongly associated with which of the following pre-existing conditions?
- A 41-year-old right-handed man is noted to speak fluently but makes frequent paraphasic errors and cannot repeat short phrases, though comprehension is largely intact. MRI reveals a small cortical infarct. Which of the following structures is most likely affected?
- A case-control study investigates whether prior concussions are associated with later diagnosis of migraine. Cases are 240 adults aged 18–50 with new migraine diagnosis from neurology clinics. Controls are 240 adults from the same clinics diagnosed with tension-type headache. Prior concussions are assessed by patient interview and review of sports medicine records when available. Results: 39% of migraine cases report ≥1 concussion vs 25% of controls. Investigators note that migraine patients may be more likely to remember head injuries. Which statistical measure best represents the outcome of this study?
- Which of the following terms best describes Drug B?
- The reduced concentration of which of the following substances in the pancreatic fluid is most indicative of pancreatic exocrine insufficiency in this patient?