All practice questions

A group of investigators is designing a case-control study to evaluate the potential association between a diet high in processed meats and the development of colorectal cancer. During the planning phase, the researchers identify regular physical activity as a major concern. Physical activity is known to be associated with both a lower intake of processed meats and a decreased risk of colorectal cancer, and it is not considered to lie on the causal pathway between the two. The researchers want to ensure that their study findings are not distorted by this variable. Which of the following methodological strategies can be appropriately utilized to control for the effect of physical activity in this study? (Select all that apply)

A retrospective cohort study evaluates the potential association between a newly marketed weight-loss medication and the incidence of new-onset atrial fibrillation. Investigators analyze the medical records of 20,000 adult patients over a 3-year follow-up period. The initial crude analysis reveals a relative risk (RR) of 2.1 ($95\%$ CI: 1.6-2.8) for developing atrial fibrillation in patients prescribed the medication compared to those not taking it. The research team subsequently stratifies the data based on the patients' baseline history of obstructive sleep apnea (OSA). In the stratum of patients with a history of OSA, the RR is 1.1 ($95\%$ CI: 0.8-1.5). In the stratum of patients without a history of OSA, the RR is 1.0 ($95\%$ CI: 0.7-1.4). Which of the following is the most appropriate interpretation of the role of OSA in this study?

Match each clinical research scenario or observation with the specific epidemiological concept, methodological phenomenon, or bias it best illustrates.

A 38-year-old male presents to the outpatient clinic for a blood pressure recheck. He has a history of hypertension that remains poorly controlled despite adherence to a regimen of amlodipine, lisinopril, and chlorthalidone at maximal therapeutic doses. His blood pressure today is 162/100 mmHg. Laboratory studies reveal a serum potassium level of 3.0 mEq/L. His chlorthalidone is discontinued, and his potassium is repleted to normal levels over the next two weeks. The physician strongly suspects an underlying endocrine etiology for his resistant hypertension. Arrange the following diagnostic steps in the most appropriate sequential order for working up this patient's suspected condition, from initial screening to definitive pre-surgical evaluation.

A 61-year-old woman is evaluated in the hospital due to an acute drop in her platelet count. She was admitted 5 days ago for a proximal right lower extremity deep vein thrombosis and was immediately started on a continuous intravenous unfractionated heparin infusion. On admission, her platelet count was $310,000/\mu \text{L}$. Today's routine complete blood count reveals a platelet count of $140,000/\mu \text{L}$. Her hemoglobin is $13.1 \text{ g/dL}$ and leukocyte count is $8,200/\mu \text{L}$. The patient reports no hematuria, melena, or mucosal bleeding. Physical examination is unremarkable with no evidence of petechiae or purpura. The clinical team suspects heparin-induced thrombocytopenia, discontinues the unfractionated heparin, and initiates an argatroban infusion. Which of the following is the most appropriate next step in laboratory evaluation to support this diagnosis?

A 68-year-old man is evaluated on the surgical ward for decreased urine output. He underwent an open cholecystectomy for acute gangrenous cholecystitis two days ago. Over the past 12 hours, his urine output has been 150 mL via the urethra after his indwelling urinary catheter was removed earlier in the day. His preoperative serum creatinine was 1.1 mg/dL, and his current serum creatinine is 2.8 mg/dL. His medical history includes hypertension, benign prostatic hyperplasia, and osteoarthritis. His perioperative medications include lisinopril, ketorolac, and piperacillin-tazobactam. Vital signs are temperature 37.1°C (98.8°F), blood pressure 135/82 mmHg, and heart rate 88/min. Physical examination shows normal skin turgor, a healing right upper quadrant incision, and dullness to percussion in the suprapubic region. Which of the following studies comprise the most appropriate initial diagnostic workup for this patient's acute kidney injury? (Select exactly 3 answers)

A randomized, double-blind, placebo-controlled trial investigates a novel oral Janus kinase (JAK) inhibitor for the treatment of moderate-to-severe plaque psoriasis. The primary endpoint is achieving a 75% reduction in the Psoriasis Area and Severity Index (PASI 75) at 16 weeks. A total of $500$ patients are randomized $1:1$ to the treatment or placebo arm. Baseline demographics and disease severity are well balanced between the two groups. During the 16-week trial period, 85 patients (34%) in the placebo group drop out, predominantly citing a perceived lack of efficacy and worsening pruritus. In contrast, only 15 patients (6%) in the treatment group drop out. The investigators conduct a 'per-protocol' analysis restricted only to participants who completed the entire 16-week follow-up. They report that the new drug is vastly superior to placebo, with a relative risk of $4.2$ (95% CI 2.8 - 6.1).

Which of the following best describes the primary threat to the validity of this study's conclusion and the most appropriate methodological approach to mitigate it?

A 34-year-old woman is evaluated in the emergency department for a two-day history of progressive left leg swelling and pain. She has a known medical history of an ischemic stroke at age 28 and three spontaneous consecutive first-trimester abortions, for which she was extensively evaluated. Outpatient serologic testing at that time confirmed high titers of anti-cardiolipin IgG, anti-beta-2-glycoprotein I IgG, and a repeatedly positive lupus anticoagulant. Her only current medication is low-dose aspirin. Vital signs are within normal limits. Physical examination reveals an erythematous, edematous left lower extremity with tenderness to palpation along the popliteal fossa. Her leg is warm, and distal pulses are palpable. Venous duplex ultrasonography confirms an occlusive thrombus in the left popliteal vein. Laboratory testing shows a normal complete blood count, normal serum creatinine, and a normal hepatic panel. Which of the following is the most appropriate pharmacologic intervention for managing this patient's acute thrombosis?

A 65-year-old man is evaluated in the clinic for a 2-week history of low-grade fever, diffuse myalgias, and a newly developed, painful rash on his legs. His past medical history is significant for hypertension, hyperlipidemia, and ischemic heart disease. Three weeks ago, he underwent left heart catheterization with coronary angiography for worsening angina, which revealed non-obstructive coronary artery disease. His medications include aspirin, metoprolol, atorvastatin, and lisinopril, all of which he has taken for several years without recent dose changes. Temperature is 37.8°C (100.0°F), blood pressure is 152/90 mm Hg, and pulse is 88/min. Physical examination reveals a violaceous, net-like reticular pattern on the skin of bilateral lower extremities. His toes are cyanotic and tender to palpation, but bilateral dorsalis pedis and posterior tibial pulses are palpable and bounding.

Laboratory studies are notable for:
Leukocytes: 11,000/mm³ (Eosinophils 14%)
Erythrocyte sedimentation rate: 75 mm/hr
Blood urea nitrogen: 42 mg/dL
Serum creatinine: 2.6 mg/dL (baseline 1.1 mg/dL)

Urinalysis shows 5-10 white blood cells/hpf, 1-2 red blood cells/hpf, and the presence of urine eosinophils.

Which of the following is the most likely diagnosis?

An ambulatory evaluation is conducted for a patient who reports a five-day history of nonproductive cough, low-grade fevers, and profound fatigue. Medical history is significant for paroxysmal atrial fibrillation, which is currently managed with sotalol and rivaroxaban. Vital signs show a temperature of 37.9°C (100.2°F), pulse of 64/min, and blood pressure of 128/82 mmHg. Pulmonary examination is notable for bilateral scattered crackles. A chest radiograph demonstrates diffuse interstitial opacities. A rapid respiratory panel returns positive for Mycoplasma pneumoniae. A 12-lead electrocardiogram performed during the visit shows normal sinus rhythm with a corrected QT (QTc) interval of 490 milliseconds. Which of the following is the most appropriate antimicrobial intervention to prescribe for this patient?

A 34-year-old woman comes to the clinic complaining of a severe, daily headache for the past 3 weeks. She describes the pain as throbbing and holocephalic. The headache is most intense when she is standing or sitting upright at her desk and significantly improves within 15 minutes of lying flat. She has tried over-the-counter analgesics, aggressive oral hydration, and bed rest over the last two weeks with minimal relief. She denies fever, visual changes, or recent trauma. Neurological examination is unremarkable. Magnetic resonance imaging (MRI) of the brain with intravenous gadolinium contrast is performed and reveals diffuse, continuous thickening and enhancement of the pachymeninges, bilateral thin subdural fluid collections, and a 6-mm downward displacement of the cerebellar tonsils. Based on the interpretation of these imaging findings, which of the following is the most appropriate next step in management?

A 68-year-old man presents to the emergency department with a 2-hour history of severe, diffuse abdominal pain. He reports two episodes of loose stool since the pain started. His medical history includes hypertension, hyperlipidemia, and atrial fibrillation. He takes amlodipine, atorvastatin, and dabigatran, but he discontinued his dabigatran 5 days ago in preparation for a screening colonoscopy that was performed yesterday. His temperature is 37.4°C (99.3°F), blood pressure is 105/65 mmHg, heart rate is 118/min and irregularly irregular, and respiratory rate is 22/min. Abdominal examination reveals mild, diffuse tenderness to deep palpation, but there is no rebound tenderness, guarding, or rigidity. Bowel sounds are hypoactive. Stool guaiac test is negative. Serum lactate is 4.5 mmol/L (normal: 0.5-2.2 mmol/L).

Arrange the following differential diagnoses in order from the highest pre-test probability to the lowest pre-test probability based on this patient's clinical presentation.

A 71-year-old male resident of a long-term care facility is transferred to the intensive care unit due to profound hypotension and altered sensorium. He has a known history of complicated nephrolithiasis and recurrent pyelonephritis. Upon arrival, his blood pressure is 74/42 mmHg, heart rate is 126/min, and respiratory rate is 26/min. His core temperature is 39.4°C (102.9°F). Initial laboratory evaluation reveals a serum lactate of 5.1 mmol/L and a marked leukocytosis. Blood and urine cultures are obtained, and broad-spectrum intravenous antimicrobial therapy is initiated without delay.

Arrange the following hemodynamic and pharmacologic interventions in the correct evidence-based sequence according to standard septic shock management guidelines. Assume the patient's mean arterial pressure (MAP) remains below 65 mmHg despite the completion of each preceding intervention.

A 54-year-old man arrives at the emergency department via ambulance with sudden-onset, severe, tearing chest pain that radiates to his interscapular region. He has a history of poorly controlled hypertension, hyperlipidemia, and a 30-pack-year smoking history. On examination, he appears diaphoretic and in severe distress. Blood pressure is 218/116 mmHg in the right arm and 224/114 mmHg in the left arm. Heart rate is 118/min and regular. A bedside focused assessment with sonography for trauma (FAST) shows no pericardial effusion. Computed tomography (CT) angiography of the chest and abdomen reveals an intimal flap originating distal to the left subclavian artery and extending to the renal arteries. Both true and false lumens are visualized, with no evidence of end-organ malperfusion.

Arrange the following pharmacologic interventions in the definitive physiological sequence required to safely stabilize this patient's condition.

A 52-year-old woman is brought to the emergency department due to worsening shortness of breath, lightheadedness, and chest pain over the past 3 days. She reports having a viral upper respiratory infection two weeks ago. On examination, her blood pressure is 88/75 mm Hg, pulse is 118/min, and respirations are 24/min. Her extremities are cool and clammy. Which of the following physical examination findings are most likely to be present in this patient? (Select exactly 3 options)

A 72-year-old man is evaluated in the surgical intensive care unit for new-onset abdominal pain and diarrhea. He is currently on postoperative day 4 following an emergency open repair of a ruptured abdominal aortic aneurysm. His medical history is significant for coronary artery disease, hypertension, and hyperlipidemia. He received perioperative prophylactic antibiotics. Temperature is 37.9°C (100.2°F), blood pressure is 110/65 mmHg, and heart rate is 112/min. Physical examination reveals lower abdominal tenderness, most pronounced in the left lower quadrant, with voluntary guarding. Laboratory studies show a leukocyte count of 16,500/mm³ and a serum lactate level of 3.8 mmol/L. Two hours later, he passes a large volume of grossly bloody stool. Based on the patient's presentation and medical history, arrange the following differential diagnoses from the most likely (highest pre-test probability) to the least likely.

A 28-year-old woman presents to the outpatient clinic for evaluation of easy bruising and heavy menstrual bleeding over the past six months. She reports that her menses now last for 8 days and require changing a super-absorbent pad every 2 hours during the heaviest days. Two weeks ago, she underwent a dental extraction that was complicated by persistent bleeding requiring packing and tranexamic acid mouthwash. She has no chronic medical conditions and takes no daily medications, though she occasionally uses ibuprofen for menstrual cramps. Family history is notable for her mother having a "bleeding problem" after childbirth.

Vital signs are within normal limits. Physical examination reveals scattered ecchymoses on her bilateral lower extremities, measuring up to 3 cm in diameter. There is no hepatosplenomegaly, joint swelling, or deformity.

Laboratory evaluation reveals the following:

A mixing study is performed, and the patient's aPTT corrects to 32 seconds when mixed 1:1 with normal pooled plasma.

Which of the following is the most likely diagnosis in this patient?

A rapid response team is activated for a hospitalized patient in their late sixties who experiences sudden-onset severe dyspnea and syncope on the third day following a total knee arthroplasty. Current vital signs reveal a blood pressure of 78/50 mm Hg, heart rate of 124/min, and oxygen saturation of 86% on high-flow oxygen. Physical examination shows pronounced jugular venous distension. Lungs are clear to auscultation bilaterally. Stat laboratory testing reveals a troponin T level of 0.08 ng/mL (normal <0.04 ng/mL). A bedside point-of-care transthoracic echocardiogram is immediately performed and demonstrates a markedly dilated right ventricle. There is severe hypokinesis of the right ventricular mid-free wall, but the right ventricular apex exhibits normal contractility. Based on these sonographic findings, which of the following is the most likely diagnosis?

A 26-year-old woman arrives at the emergency department via private vehicle complaining of sudden, severe right lower abdominal pain that began one hour ago. She reports severe dizziness and states she nearly lost consciousness while walking from the parking lot. She is 7 weeks pregnant according to her last menstrual period and has a past medical history significant for pelvic inflammatory disease. On physical examination, she is lethargic, pale, and diaphoretic. Vital signs include a temperature of 37.2 C (99.0 F), blood pressure of 74/42 mm Hg, heart rate of 140/min, respiratory rate of 24/min, and oxygen saturation of 97% on room air. Her abdomen is rigidly distended with diffuse tenderness and rebound, most prominent in the right lower quadrant. Which of the following is the most appropriate immediate next step in the stabilization and management of this patient?

A 71-year-old man presents to the clinic reporting a three-week history of progressively worsening generalized pruritus, dark urine, and pale-colored stools. He has also noticed a 5-kg (11-lb) weight loss over the past two months. He has a medical history of hypertension and osteoarthritis. He smoked one pack of cigarettes daily for 35 years but quit five years ago. Vital signs are stable. Physical examination demonstrates diffuse scleral icterus and jaundice. Abdominal examination reveals a soft, non-tender, palpable mass in the right upper quadrant.

Laboratory findings are as follows:

A transabdominal ultrasound shows marked dilation of the common bile duct and intrahepatic bile ducts, along with a markedly distended gallbladder without gallstones. The distal common bile duct and pancreas are obscured by overlying bowel gas.

Which of the following is the most appropriate next step in the diagnostic workup?