All practice questions

A physician is reviewing a pharmaceutical advertisement for a newly approved medication, cardiopril, intended for patients with stable coronary artery disease. The advertisement features a prominent graph highlighting a "$30\%$ relative risk reduction in major adverse cardiovascular events (MACE)" with a highly significant p-value ($p < 0.01$). To better understand the clinical impact, the physician examines the data table detailing the individual components of the composite MACE endpoint over the 5-year study period.

Based on the data provided, which of the following is the most accurate interpretation of the advertisement's efficacy claim?

A $68$-year-old woman with a history of congenital long QT syndrome and recurrent syncope is admitted to the hospital with community-acquired pneumonia. The physician is reviewing a pharmaceutical brochure for a newly approved fluoroquinolone derivative, levadroxacin, which is heavily marketed as being non-inferior to the standard-of-care regimen (ceftriaxone plus azithromycin). The brochure highlights the results of a randomized, double-blind trial with a prespecified non-inferiority margin ($\Delta$) of $-10\%$. The trial experienced a $22\%$ overall dropout and loss-to-follow-up rate before completion.

The brochure presents the following summary data for the primary endpoint (difference in clinical cure rate at day $14$, calculated as levadroxacin minus standard-of-care):

Based on a critical appraisal of this advertisement and the patient's medical history, which of the following is the most appropriate conclusion regarding the use of levadroxacin for this patient?

A recent multi-center, randomized, double-blind clinical trial evaluated the efficacy of a novel monoclonal antibody for the prevention of episodic migraines. The published abstract includes the following data regarding the primary endpoint:

Based on these reported event rates, what is the number needed to treat (NNT) to prevent one additional patient from progressing to chronic migraine?

A research team is analyzing serum neuronal enriched enolase (NEE) concentrations (measured in $\text{ng/mL}$) collected from $800$ patients following out-of-hospital cardiac arrest. The dataset reveals a mean NEE concentration of $45 \text{ ng/mL}$, a median of $18 \text{ ng/mL}$, and a mode of $12 \text{ ng/mL}$. The standard deviation is reported as $52 \text{ ng/mL}$. The researchers are preparing the manuscript's methods section regarding how they will summarize this baseline characteristic and compare it between patients who achieved return of spontaneous circulation and those who did not. Based on the descriptive statistics provided, which of the following is the most appropriate methodological approach?

A multidisciplinary oncology tumor board is establishing a new clinical registry to track patient outcomes, toxicities, and demographics for a novel targeted therapy protocol. To ensure proper subsequent statistical analysis, the data managers must accurately classify each collected variable. Match the following clinical variables from the registry to their most appropriate statistical data type.

A $62$-year-old woman with type 2 diabetes mellitus and essential hypertension presents for a routine follow-up. She is currently asymptomatic. Her daily medications include metformin and lisinopril. Her most recent hemoglobin A1c is $7.4\%$, and her serum creatinine is $1.2$ mg/dL. During the visit, she shows the physician a magazine advertisement for a newly approved diabetes medication, *Renagliflozin*. The advertisement features a prominent headline: "Proven to reduce major diabetic complications by 30%!" The patient asks if she should start this medication specifically to reduce her risk of having a heart attack.

The physician reviews the fine print of the advertisement, which includes a data table from the drug's pivotal randomized controlled trial comparing *Renagliflozin* to placebo over a 4-year period.

*\*The primary composite endpoint is defined as the occurrence of cardiovascular death, non-fatal myocardial infarction, non-fatal stroke, or doubling of serum creatinine.*

Based on the provided literature, which of the following is the most appropriate response to the patient's inquiry about preventing a heart attack?

A dermatology research team conducts a study comparing the efficacy of two topical immunomodulators, Agent X and Agent Y, for the treatment of severe atopic dermatitis. The study enrolls $18$ adult patients who present with symmetrical, similarly severe eczematous lesions on both their left and right antecubital fossae. For each patient, the investigators randomly assign Agent X to one arm and Agent Y to the contralateral arm.

After $6$ weeks of twice-daily application, the researchers measure the absolute reduction in the Eczema Area and Severity Index (EASI) score for each arm. Statistical evaluation reveals that the reduction scores for both treatment arms are severely non-normally distributed with a pronounced right skew. The researchers wish to determine if there is a statistically significant difference in the reduction of disease severity between the two topical treatments.

Which of the following is the most appropriate statistical test to perform this analysis?

An endocrinology department evaluates the distribution of serum thyroid-stimulating hormone (TSH) levels in a population of 3,000 asymptomatic adults. In this study, the vast majority of individuals have TSH values concentrated between 1.0 and 2.0 mIU/L. However, a small proportion of the subjects have undiagnosed subclinical hypothyroidism, yielding a long tail of TSH values ranging from 5.0 to 12.0 mIU/L. Values below 0.4 mIU/L are exceedingly rare in this cohort. Based on the shape of this distribution, which of the following is the most accurate statement regarding the descriptive statistics of the TSH data in this cohort?

A journal club meeting focuses on the critical appraisal of recent clinical studies and promotional materials. Participants are tasked with identifying the core methodological flaws, statistical misrepresentations, or biases inherent in various texts. Match each of the following literature excerpts (left) with its corresponding epidemiological concept or limitation (right).

Match each clinical research scenario with the most appropriate inferential statistical test required to analyze the resulting data. Assume all necessary assumptions for the explicitly indicated data distributions are met.

A regional health network evaluates the quality of its emergency cardiovascular care by analyzing the door-to-balloon times for $1,200$ patients presenting with ST-segment elevation myocardial infarction over the past year. The times are recorded as a continuous variable in minutes. A preliminary review of the data reveals a mode of $68$ minutes and a median of $84$ minutes. The distribution includes a long tail representing a small subset of patients transferred from remote rural facilities who experienced times exceeding $350$ minutes. The research committee is preparing a summary report for the hospital board. Based on the characteristics of this dataset, which of the following statements is most accurate regarding the statistical analysis?

A multicenter rheumatology research network is analyzing demographic data for a newly defined phenotype of large-vessel vasculitis. The registry includes $2,500$ confirmed cases. The investigators perform a descriptive analysis of the age of initial symptom onset. The resulting histogram demonstrates a normal distribution. According to the registry's statistical report, the $2.5^\text{th}$ percentile for age of symptom onset is $29$ years, and the $84^\text{th}$ percentile is $53$ years.

Based on the empirical characteristics of normal distributions, what is the mean age of symptom onset (in years) for this patient cohort?

A public health research team is conducting a cross-sectional study to evaluate patient satisfaction across three distinct models of primary care delivery: federally qualified community health centers, hospital-affiliated outpatient clinics, and private physician practices. A random sample of 150 patients (50 from each care model) completes a standardized evaluation tool. The primary outcome is the patients' overall satisfaction, recorded as a single response on a 5-point Likert scale ranging from 1 ("Completely Dissatisfied") to 5 ("Completely Satisfied"). The investigators aim to determine if there is a statistically significant difference in the distribution of satisfaction scores among the three primary care models. Which of the following is the most appropriate statistical test to conduct this analysis?

A research group is analyzing the baseline characteristics of patients enrolled in a clinical trial for a novel acute pancreatitis therapy. They measure admission serum levels of a prognostic biomarker, Protein-Z (measured in $\text{mg/dL}$), in $350$ subjects. The frequency distribution of the biomarker concentrations reveals that the majority of values are concentrated between $1.5$ and $4.0\text{ mg/dL}$, while a small number of patients have extremely high values, creating a long tail extending up to $22.0\text{ mg/dL}$.

Which of the following is the most appropriate pair of descriptive statistics to summarize these biomarker levels, and what is the expected relationship between the mean and the median in this dataset?

Investigators at a tertiary care center are assessing the utility of a new functional MRI (fMRI) protocol compared to standard electroencephalography (EEG) for identifying seizure foci in adult patients with drug-resistant epilepsy. The study enrolls $60$ patients. Each patient is evaluated with both the standard EEG and the new fMRI protocol. The interpreting clinicians classify each patient's results as either 'focal abnormality identified' or 'no focal abnormality identified' for both modalities. The researchers plan to analyze the data to determine if there is a statistically significant difference in the proportion of focal abnormalities detected by the new fMRI protocol compared to the standard EEG. Which of the following is the most appropriate statistical test to analyze these study results?

A critical care research network is designing a prospective database to evaluate outcomes in patients admitted with severe sepsis. The investigators are mapping out their data analysis plan and must correctly identify the statistical nature of each variable to ensure appropriate descriptive statistics and hypothesis tests are selected. Match each collected clinical variable with its correct statistical data classification.

A multidisciplinary research consortium is analyzing data from several distinct clinical protocols to prepare for publication. To ensure validity, the statistical methods must strictly adhere to the assumptions of the underlying data distributions and study designs. Which inferential statistical test is the most methodologically sound for the primary analysis of each described study design and dataset below?

A prospective cohort study is conducted to evaluate the association between chronic proton pump inhibitor (PPI) use and the incidence of gastric adenocarcinoma over a 15-year period.

Initial analysis reveals a crude relative risk (RR) of $2.8$ (95% CI: $2.1$ - $3.7$) for gastric adenocarcinoma in chronic PPI users compared to non-users. Concerned about the potential influence of Helicobacter pylori infection, the investigators perform a stratified analysis.

Among patients with confirmed H. pylori infection, the RR for developing gastric adenocarcinoma with chronic PPI use is $1.1$ (95% CI: $0.8$ - $1.5$). Among patients without H. pylori infection, the RR is $1.2$ (95% CI: $0.9$ - $1.6$).

Based on these stratified results, which of the following is the most appropriate approach for the investigators regarding the final analysis and reporting of this data?

A primary care clinic is conducting a journal club on a newly published, randomized, double-blind, placebo-controlled trial. The trial evaluates a novel antiplatelet medication, 'Thrombo-Block', for the prevention of secondary ischemic stroke following a transient ischemic attack (TIA).

The study's promotional materials heavily emphasize a relative risk reduction of $50\%$ ($p < 0.01$) for ischemic stroke.

A detailed review of the manuscript reveals the following:
- The absolute incidence of ischemic stroke over $3$ years was $4\%$ in the placebo group and $2\%$ in the Thrombo-Block group.
- A subgroup analysis stratified patients by the presence of chronic kidney disease (CKD).
- In the CKD subgroup, the relative risk (RR) for stroke with Thrombo-Block versus placebo was $0.95$ ($95\%$ CI: $0.80 - 1.10$).
- In the non-CKD subgroup, the RR was $0.25$ ($95\%$ CI: $0.10 - 0.40$).

Following the presentation, the clinical team discusses a $68$-year-old male patient with a recent TIA, baseline CKD (stage $3$), and a history of severe recurrent gastrointestinal hemorrhage.

Which of the following statements regarding the study results and their application is most accurate?

Clinical researchers are evaluating the real-world effectiveness of a novel immunotherapy agent versus standard chemotherapy in patients with stage IV non-small cell lung cancer. The study is a prospective observational cohort. The primary endpoint is overall survival, which is defined as the time from the initiation of therapy until death from any cause. Patients who are still alive at the end of the five-year study period, or who are lost to follow-up prior to that time, are censored in the analysis. Because treatment assignment was not randomized, the investigators must statistically adjust for significant baseline differences observed between the two treatment arms. Specifically, they need to control for patient age, baseline Eastern Cooperative Oncology Group (ECOG) performance status, and lifetime pack-years of smoking. Which of the following statistical methods is most appropriate to evaluate the primary endpoint in this study?