Exam 4: Biostatistics

A clinical study examines the usefulness of 5 different biomarkers to detect Barrett esophagus (BE), the only known precursor lesion of esophageal adenocarcinoma.  Researchers evaluate the performance of each biomarker and report the sensitivity, specificity, and area under the curve (AUC) estimates. Which of the biomarkers is most accurate?

Pulmonary capillary wedge pressure (PCWP) measurements can be used to estimate left atrial pressure; the normal range is between 6-12 mm Hg, and recorded values are whole numbers.  A patient in the intensive care unit has 20 serial PCWP measurements taken over the course of 2 hours.  Among these 20 observations, the maximal recorded value is 12 mm Hg and the minimal recorded value is 10 mm Hg.  If the next measurement is 26 mm Hg, which of the following is most likely to remain unchanged?

Researchers conduct a randomized controlled trial to determine whether prophylactic administration of tranexamic acid (TXA) in addition to prophylactic oxytocin in women undergoing vaginal delivery has an effect on the incidence of postpartum hemorrhage (PPH), defined as blood loss ≥500 mL.  Study participants are women in labor who have a planned vaginal delivery of a live singleton at ≥35 weeks gestation.  They are randomly assigned to receive 1 g TXA or placebo intravenously in addition to prophylactic oxytocin after delivery.  The relative risk of PPH among women receiving TXA in addition to oxytocin is 0.80 (95% confidence interval of 0.66-0.96).  Which of the following is the most appropriate conclusion about the effect of TXA in addition to prophylactic oxytocin after delivery on the risk of PPH?

A study is designed to evaluate the efficacy of a new drug, KM28.  The study will compare KM28 plus standard care versus standard care alone with regard to decreasing the incidence of recurrent breast cancer.  The Food and Drug Administration (FDA) will approve the new drug if KM28 plus standard care decreases the rate of breast cancer recurrence by at least 40% compared to standard therapy alone.  The recurrence rate on standard therapy is found to be 8%.  In order for the FDA to approve KM28, what is the maximal incidence of recurrent disease acceptable for women treated with KM28 plus standard therapy?

A 45-year-old man comes to the office for a routine visit.  The patient has a first-degree relative with Alzheimer dementia and is concerned about his chances of developing the disease.  He has read in the newspaper that decreased consumption of yellow and orange fruits and vegetables has been associated with Alzheimer disease and would like to know how likely he is to develop the disease.  A medical literature review uncovers a recent cohort study that evaluated the association between blood carotene concentration and Alzheimer disease.  The development of the disease was evaluated in a 20-year follow-up study of 200 middle-aged subjects who have a first-degree relative with Alzheimer disease.  The results are as follows: Assuming the patient has low carotene levels, what is his 20-year risk of developing Alzheimer disease?

Drugs A and B are 2 new experimental drugs being tested for the treatment of a novel respiratory viral infection that causes acute respiratory failure and death in children.  Part of the testing process is to analyze the 2-week survival after treatment to determine the clinical efficacy of the experimental drugs.  A total of 60 children recently diagnosed with the disease are randomly assigned in a 1:1:1 ratio to receive Drug A, Drug B, or placebo.  The absolute risk reduction of Drug A compared to placebo was found to be 0.05, whereas the absolute risk reduction of Drug B compared to placebo was found to be 0.20.  Based on these results, which of the following statements comparing the effectiveness of Drugs A and B in treating children infected with the novel virus is most appropriate?

Zeracizumab is an experimental angiogenesis inhibitor targeting vascular endothelial growth factor that is being tested for the treatment of advanced, chemotherapy-naive, non-squamous non-small cell lung cancer (NSCLC).  Part of the drug company's evaluation process is to analyze the 1-year survival after treatment to determine the clinical efficacy of the experimental treatment.  The results are given in the table below. Which of the following best represents the number needed to harm for the zeracizumab-containing regimen?

A pediatrician examines a population of 1,000 children with a new test to diagnose asthma.  The prevalence of asthma in this population is 10%.  The sensitivity of the pediatrician's diagnostic test is 95%, and the specificity is 80%.  Which of the following is the likelihood that a child from this population with a positive test result really has asthma?

Researchers are interested in the association between colorectal carcinoma and nonsteroidal anti-inflammatory drug use.  They first interview a group of patients with biopsy-proven colorectal carcinoma and then interview a group consisting of the patients' neighbors who are of similar age and race.  The analysis is based on comparing the results of pairs of individuals (one from each of the 2 groups) who have similar characteristics.  This design technique best helps address which of the following potential problems with this study?

A pediatric cardiologist decides to determine whether there is a relationship between body composition and blood pressure in a random sample of children and adolescents age 5-15.  He used standard procedures to collect anthropometric measurements that included weight, height, hip circumference (HC), and waist circumference (WC).  Systolic blood pressure (SBP) and diastolic pressure (DBP) readings were taken at least 3 times at 5-minute intervals after the participants had been seated, and average SBP and DBP readings were calculated based on these measurements.  Which of the following statistical tests is adequate to determine whether there is a relationship between WC and average DBP?

A 45-year-old woman comes to the office with a palpable thyroid node.  Medical history reveals that she was diagnosed with medulloblastoma during childhood and treated with chemotherapy and external beam radiation.  Fine-needle aspiration of the thyroid shows no malignant cells.  As the test results are explained to the patient, she asks, "What are the chances that I really do not have thyroid cancer?"  Which of the following diagnostic test parameters would be most useful for answering this patient's question?

A new portable cholesterol-measuring device is being developed for use in medically underserved communities.  During clinical trials of an early prototype, a patient's cholesterol level is found to be 200 mg/dL, 201 mg/dL, and 200 mg/dL on 3 separate measurements of the same blood sample.  Using the gold standard measurement method, the same sample is found to have a cholesterol level of 260 mg/dL.  Which of the following descriptions best characterizes the new cholesterol-measuring device?

An 89-year-old man is brought to a geriatric clinic by family members who are concerned that he is developing dementia due to recent worsening of his memory.  The attending physician uses a new cognitive test (test X) to help rule out the possibility of dementia.  The patient's test result is negative.  A study evaluating the efficacy of test X in a sample of 200 individuals age >85, in which the prevalence of dementia is 50%, has determined that the test has a specificity of 80% and a sensitivity of 90%.  Assuming that this patient's pretest probability of having dementia is equivalent to the disease prevalence in the study population, what is the probability that this patient truly does not have dementia?

Researchers studying the effects of hormone replacement therapy (HRT) on the risk of myocardial infarction (MI) among postmenopausal women calculate the relative risk (RR) of MI to be 1.30 (p = 0.07) among women who are taking HRT compared to those who are not.  The researchers conclude that there is no statistically significant increased risk of MI with HRT (based on a cutoff of α = 0.05).  Subsequently, the results of a meta-analysis determine that there actually is an increased risk of MI, with an overall RR = 1.32 (p = 0.03) among postmenopausal women who are taking HRT compared to those who are not.  Which of the following was the most likely problem in the first study?

A prospective cohort study was conducted to assess the role of daily alcohol consumption in the occurrence of breast carcinoma.  The investigators reported a 5-year relative risk of 1.4 for people who consume alcohol daily compared to those who do not.  The 95% confidence interval was 1.02-1.85.  Which of the following p-values is most consistent with the results described above?

Researchers want to study the effects of labyrinthectomy with cochlear implantation on hearing, vertigo, and tinnitus.  A random sample of medical charts is selected from a cohort of patients who had undergone labyrinthectomy with cochlear implantation in the same ear for intractable vertigo and hearing loss and who had documentation of both preoperative and postoperative audiometric evaluations.  Tinnitus is quantified using the Tinnitus Handicap Inventory (THI) before and after the interventions.  The THI score ranges from 0 to 100, with higher values indicating greater tinnitus severity.  Which of the following statistical tests is most appropriate for comparing preoperative and postoperative THI scores?

The figure below shows the estimated incidence and mortality in 2019 for the 3 most common cancers affecting women in the United States, based on the American Cancer Society's Cancer Facts & Figures 2019.  The x-axis lists the specific cancers, and the y-axis shows the projected number of patients affected. Which of the following lists of cancers most likely corresponds to Cancers 1, 2, and 3, respectively?