All practice questions

A local public health department evaluates a community-based dietary intervention aimed at reducing fasting blood glucose levels in patients with prediabetes. A preliminary study of $36$ participants reveals a mean fasting blood glucose reduction of $18.0$ mg/dL after 6 months. The reported 95% confidence interval for this mean reduction is $12.0$ to $24.0$ mg/dL.

Based on these promising results, the investigators are planning a larger follow-up study using an identical intervention in the same population. They assume the population variance will remain exactly the same and that the standard normal distribution (z-score) will be used to construct the confidence intervals in both analyses.

If the follow-up study successfully enrolls and analyzes $144$ participants, what will be the total width of the 95% confidence interval for the mean reduction in fasting blood glucose in the new study?

Match each clinical research scenario with the epidemiologic study design that best describes its methodology.

A 12-month-old boy is brought to the clinic for a routine well-child visit. He was diagnosed with perinatal HIV infection at age 2 months. His mother has a history of HIV and intravenous drug use but is currently in a methadone maintenance program. The patient is maintained on combination antiretroviral therapy. His most recent laboratory studies from two weeks ago show a CD4+ T-lymphocyte percentage of 10% and an absolute CD4+ count of 250/mm³. He has received all routine immunizations up to his 6-month visit. Temperature is 37.1°C (98.8°F), blood pressure is 90/55 mmHg, pulse is 110/min, and respirations are 24/min. Physical examination today is unremarkable. Which of the following vaccines is most appropriate to administer to this patient at this visit?

Emergency medical services arrive at the trauma bay with a 78-year-old man who developed sudden, excruciating, and diffuse abdominal pain two hours ago. He has a known history of severe coronary artery disease and noncompliant medication management for atrial fibrillation. Upon arrival, he appears ashen, profoundly lethargic, and diaphoretic. Vital signs include a temperature of 37.8°C, an irregularly irregular pulse of 132/min, a blood pressure of 82/50 mm Hg, and respirations of 24/min. Abdominal examination demonstrates striking rigidity with widespread guarding and rebound tenderness in all four quadrants. Initial point-of-care testing reveals a serum lactate of 9.4 mmol/L and a marked leukocytosis of 22,000/mm³. An electrocardiogram shows atrial fibrillation with rapid ventricular response. Arrange the following interventions in the most appropriate chronological sequence for the definitive management of this patient.

A $62$-year-old postmenopausal woman is evaluated in the clinic for hypercalcemia found on routine laboratory screening. She is entirely asymptomatic and has no history of nephrolithiasis, fragility fractures, or abdominal pain. Her serum calcium is $10.9$ mg/dL (normal range: $8.4-10.2$ mg/dL), albumin is $4.0$ g/dL, and intact parathyroid hormone (PTH) is $115$ pg/mL (normal range: $10-65$ pg/mL). Renal function is normal. Arrange the following steps in the most appropriate chronological sequence for the diagnostic workup and surgical management of this patient.

A pharmacovigilance team is investigating a potential link between a newly introduced fluoroquinolone antibiotic and the development of Achilles tendon rupture. The investigators access a large, national commercial insurance database containing continuous enrollment and claims data. They first identify 850 patients in the database who had a diagnostic code for Achilles tendon rupture between 2020 and 2025. Next, they select 3,400 patients from the same database who did not experience this injury, matching them to the initial group by age, sex, and geographic region. Finally, the investigators review the historical pharmacy claims data for all 4,250 selected individuals to determine whether they were prescribed the fluoroquinolone in the 6 months prior to the index date of tendon rupture or the equivalent matched date. Based on the methodology described, which of the following is the most appropriate primary measure of association to calculate for this investigation?

Following a high-speed motorcycle collision, a male patient in his mid-twenties arrives at the trauma resuscitation bay. He is lethargic and responds only to painful stimuli. Vital signs include a blood pressure of $76/40\text{ mmHg}$, heart rate of $135/\text{min}$, respiratory rate of $26/\text{min}$, and temperature of $36.5^\circ\text{C}$ ($97.7^\circ\text{F}$). Physical assessment reveals profound ecchymosis over the suprapubic and perineal areas, accompanied by visible blood at the urethral meatus. Gentle anteroposterior compression of the iliac crests demonstrates gross mechanical instability of the pelvic ring. A bedside focused assessment with sonography for trauma (FAST) shows no anechoic fluid in the peritoneal spaces. Massive transfusion protocol is initiated via two large-bore peripheral intravenous catheters. Which of the following is the most appropriate next step in the management of this patient?

Match each clinical presentation of urolithiasis with the most appropriate definitive surgical or procedural management.

A clinical investigator is presenting findings from a retrospective cohort study at a surgical conference. The study aimed to evaluate whether a newly implemented anesthetic protocol reduces the incidence of postoperative nausea and vomiting (PONV) in patients undergoing laparoscopic cholecystectomy. The investigator presents the following data collected from electronic health records:

During the presentation, the investigator concludes: "Our statistical analysis demonstrates an odds ratio of $0.33$ for the modified protocol. This indicates that patients receiving the new protocol have a $67\%$ lower risk of developing PONV compared to those receiving the standard protocol."

Which of the following is the most accurate critique of the investigator's conclusion?

An infectious disease ward at a metropolitan hospital frequently evaluates patients presenting with presumed bacterial meningitis. During the winter season, epidemiological records indicate that $20\%$ of these admitted patients are ultimately confirmed to have a bacterial etiology via standard cerebrospinal fluid (CSF) culture. To expedite initial patient management, the hospital introduces a rapid CSF polymerase chain reaction (PCR) panel. Clinical validation of this rapid PCR panel demonstrates a sensitivity of $80\%$ and a specificity of $95\%$. If this rapid PCR panel is applied to a representative cohort of $1,000$ such admissions, what is the expected positive predictive value (expressed as a percentage) of a positive test result?

A triage nurse immediately calls a surgical code for a patient who just collapsed in the hospital waiting room. The patient, a 72-year-old male with a history of hypertension and tobacco use, was initially presenting for evaluation of sudden, tearing flank pain. Vital signs on the monitor show a heart rate of 128/min and a blood pressure of 72/38 mm Hg. The patient is confused and visibly diaphoretic. Physical examination reveals a large, expansile periumbilical mass. Arrange the following steps in the most appropriate chronological sequence for the optimal management of this hemodynamically unstable patient's condition.

A 52-year-old woman is evaluated in the neurosurgical intensive care unit for new-onset neurological deficits. Six days ago, she was admitted for a subarachnoid hemorrhage and underwent successful endovascular coiling of a ruptured anterior communicating artery aneurysm. Her postoperative course was initially uncomplicated, and she has been receiving standard medical therapy. Over the past 2 hours, she has become increasingly lethargic and developed right-sided weakness. Her temperature is 37.2°C (99.0°F), blood pressure is 112/72 mm Hg, and pulse is 84/min. Physical examination confirms right-sided hemiparesis and expressive aphasia. A noncontrast CT scan of the head reveals the coiled aneurysm with no new bleeding, hydrocephalus, or territorial infarction. Which of the following is the most appropriate next step in management?

A 28-year-old man is brought to the emergency department 30 minutes after sustaining a stab wound to his right medial thigh. He reports excruciating pain in his right leg. His blood pressure is $118/76$ mm Hg, and his heart rate is $102$/min. Physical examination reveals a 3-cm linear laceration over the right anteromedial thigh. There is a rapidly expanding, pulsatile hematoma surrounding the wound. Palpation of the right lower extremity reveals absent dorsalis pedis and posterior tibial pulses, whereas the left lower extremity pulses are normal and symmetric. The right foot is pale and cool to the touch compared to the left. Which of the following is the most appropriate next step in the management of this patient?

Match each patient presentation with the most appropriate primary preventive screening recommendation based on current United States Preventive Services Task Force (USPSTF) guidelines.

Match each patient presentation to the most appropriate, guideline-based clinical preventive screening test indicated at their current visit based on United States Preventive Services Task Force (USPSTF) recommendations.

A 34-year-old man presents to the emergency department with a painful, persistent erection that began 8 hours ago without sexual stimulation. He has a history of sickle cell trait. Physical examination reveals fully rigid, exquisitely tender corpora cavernosa and a flaccid glans penis. Arrange the following diagnostic and therapeutic steps in the optimal chronological sequence for managing this acute urologic emergency, progressing from initial evaluation to definitive refractory management.

A 72-year-old man is admitted to the hospital with a complicated urinary tract infection. Urine cultures grow *Escherichia coli*. The susceptibility report indicates the organism is susceptible to narrow-spectrum oral cephalexin. The attending physician intends to prescribe cephalexin, but a recent electronic health record (EHR) system update has altered the default order sets. Due to a mapping glitch, selecting "UTI targeted therapy" auto-populates a 14-day course of broad-spectrum intravenous piperacillin-tazobactam. The physician signs the order without noticing the discrepancy, and the medication is administered. Three days later, the patient develops severe diarrhea and is diagnosed with a *Clostridioides difficile* infection. The incident is flagged for review. Which of the following is the most appropriate next step for the hospital's patient safety committee?

A 51-year-old woman is admitted to the surgical ward with a 24-hour history of severe abdominal pain, nausea, and obstipation. She has not passed flatus since the symptoms began. Her past medical history is significant for an open appendectomy for perforated appendicitis 15 years ago. The pain was initially intermittent and crampy but transitioned to a continuous, dull ache over the past 4 hours. Temperature is $37.4^\circ\text{C}$ ($99.3^\circ\text{F}$), blood pressure is $138/82\text{ mmHg}$, pulse is $92/\text{min}$, and respiratory rate is $16/\text{min}$. On physical examination, the abdomen is moderately distended and tympanitic. There is focal tenderness to deep palpation in the right lower quadrant, but no rebound tenderness, rigidity, or guarding. Bowel sounds are high-pitched and tinkling. Laboratory studies show a leukocyte count of $10,500/\text{mm}^3$ and a serum lactate level of $1.5\text{ mmol/L}$ (normal: $0.5-2.2\text{ mmol/L}$). An intravenous contrast-enhanced CT scan of the abdomen and pelvis reveals a transition point in the distal ileum. Proximal to this point, a distinct, radially distributed, C-shaped cluster of fluid-filled small bowel loops is visualized. The mesenteric vessels supplying this segment demonstrate a converging, twisted configuration. The bowel wall of the involved segment shows normal contrast enhancement, and there is no pneumatosis intestinalis. Which of the following is the most appropriate next step in management?

A $55$-year-old woman is evaluated on postoperative day $4$ following an open low anterior resection for locally advanced rectal cancer. She reports new-onset, constant, right-sided flank pain and mild nausea that began yesterday. Her temperature is $38.1^\circ\text{C}$ ($100.6^\circ\text{F}$), blood pressure is $125/75\text{ mmHg}$, and pulse is $92/\text{min}$. Physical examination reveals a clean midline abdominal incision with normal, active bowel sounds. There is distinct right costovertebral angle tenderness, but no rebound tenderness or guarding. A urethral Foley catheter was removed on postoperative day $2$, and the patient has since been voiding spontaneously with an output of approximately $450\text{ mL}$ every $8$ hours. Laboratory studies show a serum creatinine of $0.9\text{ mg/dL}$ (baseline $0.8\text{ mg/dL}$) and a leukocyte count of $12,500/\mu\text{L}$. Urinalysis shows $2$-$3$ white blood cells/hpf and no bacteria. Which of the following is the most appropriate next step in management?

A team of public health researchers conducts a retrospective cohort study using electronic health records to evaluate the effectiveness of a novel biologic therapy compared to standard inhaled corticosteroids (ICS) for preventing severe asthma exacerbations. The primary outcome is the incidence of asthma exacerbations requiring emergency department visits over a 12-month period.

Initial analysis of the data yields a crude relative risk (RR) of 1.65, suggesting that patients receiving the novel biologic have a higher risk of exacerbations compared to those receiving standard ICS.

Concerned about potential baseline differences between the treatment groups, the researchers perform a stratified analysis based on the patients' history of hospitalizations for asthma in the prior year (a marker of baseline disease severity). The results of the stratified analysis are as follows:

- Patients with $\geq 1$ prior hospitalization: $RR = 0.75$
- Patients with 0 prior hospitalizations: $RR = 0.72$

Which of the following epidemiologic phenomena best explains the difference between the crude and stratified relative risks?