USMLE Step 3

A new screening test for colorectal cancer is being evaluated. In a study of 10,000 patients, the test results were compared to colonoscopy (gold standard). The screening test was positive in 180 patients, of whom 90 had cancer on colonoscopy. The test was negative in 9,820 patients, of whom 40 had cancer on colonoscopy. What is the negative predictive value of this screening test?

• A89.5%
• B90.0%
• C95.5%
• D99.6%

A pharmaceutical company is testing a new drug for migraine prevention. The primary outcome is reduction in migraine frequency. The study enrolls 400 patients: 200 receive the new drug and 200 receive placebo. After 6 months, 120 patients in the treatment group and 80 in the placebo group show ≥50% reduction in migraine frequency. What is the number needed to treat (NNT)?

• A2
• B3
• C4
• D5

A case-control study examines the association between NSAID use and peptic ulcer disease. Cases (n=200) are patients with confirmed peptic ulcers; controls (n=400) are age-matched patients without ulcers. The study finds that 120 cases and 80 controls reported regular NSAID use. What measure of association can be calculated from this study design?

• ARelative risk
• BOdds ratio
• CAttributable risk
• DIncidence rate

A randomized controlled trial of a new anticoagulant for stroke prevention in atrial fibrillation reports the following results: 2.5% annual stroke rate in the treatment group vs. 4.0% in the warfarin control group (p=0.02). The 95% confidence interval for the relative risk reduction is 15% to 55%. Which conclusion is most appropriate?

• AThe new drug is superior to warfarin
• BThe new drug is equivalent to warfarin
• CThe new drug is non-inferior to warfarin
• DNo conclusion can be drawn due to wide confidence intervals

A screening program for breast cancer using mammography is implemented in a community. The test has 85% sensitivity and 90% specificity. If the prevalence of breast cancer in this population is 1%, what is the probability that a woman with a positive screening test actually has breast cancer?

• A1%
• B8%
• C15%
• D79%

In a meta-analysis of 15 randomized trials comparing two antihypertensive medications, a funnel plot shows asymmetry with smaller studies disproportionately favoring the newer agent. What is the most likely explanation for this finding?

• APublication bias
• BHeterogeneity between studies
• CRandom error
• DConfounding by indication

A cohort study follows 5,000 smokers and 5,000 non-smokers for 10 years to assess lung cancer incidence. At year 5, 20% of smokers quit smoking. At the end of the study, 250 smokers and 25 non-smokers developed lung cancer. Which of the following best describes the impact of the smokers who quit?

• ASelection bias
• BInformation bias
• CConfounding
• DLead-time bias

A 45-year-old man is brought to the emergency department after a motor vehicle accident. He has multiple injuries and requires emergent surgery. The patient is unconscious and no family members are present. According to emergency consent doctrine, what is the appropriate next step?

• AWait for family to arrive before proceeding
• BProceed with treatment under implied consent
• CObtain a court order
• DContact the hospital ethics committee

A 16-year-old girl requests oral contraceptives during a clinic visit. She asks that her parents not be informed. In which situation may the physician legally provide treatment without parental consent?

• ANever; minors always require parental consent
• BIf state law permits contraceptive services for minors
• COnly if the minor is pregnant
• DOnly with court authorization

A 68-year-old man with advanced dementia is admitted to the hospital with pneumonia. His wife, who is his healthcare proxy, requests that antibiotics be withheld based on his previously stated wish to avoid aggressive treatment. The patient's adult children disagree and demand antibiotics be started. What is the most appropriate action?

• AFollow the wife's decision as the designated proxy
• BFollow the children's wishes as they represent the majority
• CRequest a court to appoint a guardian
• DTreat with antibiotics and address conflict later

A physician discovers that a colleague has been prescribing opioids to family members without documenting medical indications. The colleague dismisses the concern, stating "it's just family." What is the physician's professional obligation?

• AReport to the state medical board immediately
• BReport to a supervisor or institutional authority
• CConfront the colleague again and document
• DDo nothing as it involves family members

A pharmaceutical representative offers a physician an all-expenses-paid trip to a medical conference in exchange for agreeing to prescribe their new medication. The medication is FDA-approved and clinically appropriate. Which ethical principle is most directly violated?

• ABeneficence
• BNon-maleficence
• CAutonomy
• DJustice

A patient with terminal cancer tells the physician, "I don't want any more chemotherapy. I want to go home and spend my remaining time with family." The patient's spouse insists on continuing aggressive treatment. What is the most appropriate physician response?

• AHonor the patient's wishes and transition to hospice care
• BContinue chemotherapy at a reduced dose
• CRequest a psychiatric evaluation for depression
• DSeek a court order for continued treatment

A 35-year-old woman with depression is started on fluoxetine. At a follow-up visit 4 weeks later, she appears distressed and states, "The medication isn't working and my boss wants to fire me." She asks the physician to write a note excusing her from work for 2 weeks. What is the most appropriate initial response?

• AWrite the note as it supports recovery
• BDecline and adjust the antidepressant dose
• CExplore her concerns and assess functional impairment
• DRefer to occupational medicine for evaluation

A 62-year-old man presents with sudden onset chest pain radiating to his back. Blood pressure is 168/98 mmHg in the right arm and 140/88 mmHg in the left arm. A diastolic murmur is heard at the left sternal border. What is the most likely diagnosis?

• AAortic dissection
• BAcute myocardial infarction
• CPericardial tamponade
• DHypertrophic cardiomyopathy

A 58-year-old woman with atrial fibrillation on warfarin presents with acute right-sided weakness and aphasia. CT head shows no hemorrhage. INR is 1.4. Blood pressure is 185/110 mmHg. What is the most appropriate immediate management?

• AAdminister IV tPA immediately
• BLower blood pressure to <185 systolic, then consider tPA
• CGive aspirin 325 mg and observe
• DPerform emergent CTA before any treatment

A 45-year-old man is brought to the ED after a syncopal episode. ECG shows irregular wide-complex tachycardia at 220 bpm with varying QRS morphologies. The patient is alert with BP 98/60 mmHg. What is the most appropriate treatment?

• AAdenosine 6 mg IV push
• BSynchronized cardioversion
• CAmiodarone 150 mg IV
• DDefibrillation (unsynchronized)