A study to assess spironolactone’s efficacy in patients with heart failure is performed. 450 patients receive either spironolactone or placebo for two years. Neither the patients nor physicians are aware of who takes the drug or placebo. The study setup described above is most effective in preventing:

A study investigating a new test for diagnosing acute myocardial infarction (AMI) has just been initiated. The sensitivity of the test is estimated at 75% and the specificity at 80%. The study enrolls 600 patients, of whom 200 are confirmed AMI cases as determined by the diagnostic gold standard. How many false negatives are to be expected in the study?

Officials of a public health department report a higher than normal prevalence of acute myelogenous leukemia (AML) among children age 5-12 in their community. They observe that some households in the community are exposed to chemical waste from a nearby factory and worry that exposure to this waste is responsible for the increased prevalence of AML. A case-control study is designed to evaluate the health department officials’ claim that exposure to chemical waste is associated with AML in childhood. Which of the following populations should be selected as the control group?

A new biomarker has been identified that allows for the early detection of invasive gastric carcinoma. It has a sensitivity of 89% and a specificity of 85% when compared to endoscopy with multiple biopsies. The test is used in 2 groups: a population in the United States, where 5 out of 100,000 people have gastric cancer, and a population in China, where 100 out of 100,000 people have been diagnosed with the disease. Which of the following is the most accurate statement concerning this new test?

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?

A sample of children age 2-5 years is chosen at random from an outpatient clinic.  The number of urinary tract infections (UTIs) over a 1-year period is given in the figure below.

What was the average number of UTI episodes over 1 year for a child in this sample?

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 estrogen receptor agonist is being evaluated for the treatment of postmenopausal symptoms. A prospective study shows that the drug increases the risk of deep vein thrombosis (DVT) in treated women who smoke compared to untreated women who smoke, with a relative risk (RR) of 1.70 and p-value of 0.01. In nonsmokers, no increased risk of DVT is evident with use of the drug (RR = 0.96; p-value = 0.68). Which of the following describes this phenomenon?

Inflammatory biological markers are clinically useful in a number of different ways, one being the assessment of disease activity in conditions such as systemic lupus erythematosus (SLE).  A new inflammatory marker is being investigated in patients with active SLE flares.  When the blood level of the new marker (in mg/L) is plotted against the C-reactive protein (CRP) level (also in mg/L), the following plot is obtained:

Based on the plot, the correlation coefficient between the 2 variables is closest to which of the following values?

A researcher is interested in studying whether there is an association between neural tube defects and use of acetaminophen during the first 3 months of pregnancy. He randomly chooses a group of women who have just delivered babies with neural tube defects, and a second group of women who delivered apparently healthy babies. These 2 groups were then asked about their use of acetaminophen during the first 3 months of pregnancy. Which of the following measures of association are the investigators most likely to report?

Plasma homocysteine levels are measured in patients with acute coronary syndrome who are treated at a large community hospital. The mean plasma homocysteine level in this group is determined to be 11.1 µmol/L with a standard deviation of 1.2 µmol/L. In a separate group of patients hospitalized on the general ward in the same hospital, the mean plasma level is 9.5 µmol/L and the standard deviation is 1.3 µmol/L. Which of the following statistical methods should be used to compare the mean homocysteine levels of these 2 groups of patients?

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 case-control study was conducted to estimate the association between simvastatin therapy and serum levels of fibrinogen in patients who underwent percutaneous coronary intervention.  Cases were identified as patients who underwent percutaneous coronary intervention and had high periprocedural levels of fibrinogen (>400 mg/dL), and controls were identified as patients who underwent percutaneous coronary interventions but had normal levels of fibrinogen (200-400 mg/dL).  History of simvastatin therapy use was assessed through chart review for every patient.  The number of patients corresponding to each classification criteria is given in the table below.

Which of the following is the best statistical method to estimate the association between simvastatin use and high serum fibrinogen levels in this study?

A 50-year-old man comes to the physician for a routine check-up. He has a 20-pack-year smoking history and consumes alcohol occasionally. He eats a balanced diet and consumes fried foods and red meat several times a week. He is not very active and spends much of his free time watching television and sitting at his computer. His family history is significant for hypertension in his mother and bladder cancer in his father. His blood pressure is 160/90 mm Hg and heart rate is 70/min. Laboratory testing is significant for a fasting blood glucose level of 155 mg/dL. Which of the following interventions is likely to have the greatest effect on reducing this patient’s mortality risk?

An intern in the endocrinology department is asked to complete a chart review of cholesterol levels of all patients hospitalized with diabetes mellitus-related cardiovascular complications in the past 6 months. The intern’s preliminary data analysis reveals that there were 400 such patients, and that serum cholesterol levels were normally distributed among the patients with a mean of 220 mg/dL and a standard deviation of 10 mg/dL. Based on these results, how many patients in this study would be expected to have serum cholesterol >240 mg/dL?

A study is conducted to assess the effect of beta-blocker therapy in patients with acute myocardial infarction (MI). The study found that 20 patients out of 90 who took a beta-blocker during the week prior to developing an MI had a major arrhythmia event during hospitalization. The study also determined that 30 patients out of 70 who did not take any beta-blocker developed a major arrhythmia. What was the odds ratio of developing major arrhythmia in patients who took beta-blockers compared to those who did not take beta-blockers?

A state’s population for 2016 was estimated at 4,000,000. At the beginning of the same year, the state reported having 20,000 cases of a rare and fatal neurodegenerative condition. At the end of 2016, the state reported 7,000 new cases, as well as 1,000 deaths attributable to this condition. Another 40,000 deaths from all other causes were also reported at the end of the year. What was the cumulative incidence of the disease in 2016?

400 women aged 20-35 coming for routine check-up are asked about their smoking status. 40% of the women are smokers. Over the next ten years, 25 smokers and 24 non-smokers developed breast cancer. Which of the following best describes the study design?

The results of a study investigating a new diagnostic test for acute myocardial infarction (MI) are given in the table below.

What is the sensitivity of the new diagnostic test?

Researchers are developing an enzyme-linked immunosorbent assay test for diagnosing rheumatoid arthritis. The test is designed to detect the presence of serum antibodies against citrullinated proteins. Two test populations with a differing prevalence of rheumatoid arthritis are selected. The researchers plan to assess the test’s performance in the 2 populations by comparing a number of diagnostic test parameters. Which of the following performance measures is most likely to be different between the 2 test populations?

A large study of serum folate levels in a sample of women age 16-45 reveals that this parameter is normally distributed with a mean of 5.0 ng/mL and a standard deviation of 0.5 ng/mL. According to the study results, 95% of serum folate observations in these patients will lie approximately between which of the following limits?

A study is performed to compare the effect of tramadol when compared to placebo for painful polyneuropathy. Fifty patients are selected and randomly allocated to 1 of 2 treatment sequences: Tramadol followed by placebo, or placebo followed by tramadol. The initial treatment period is delivered for 4 weeks followed by an interim 1-week washout phase, after which the second treatment period is delivered for an additional 4 weeks. After each treatment period, patients use a 10-point numeric scale to rate pain, paresthesia, and tenderness. Which of the following best describes this study design?

A researcher studying physician behavior is interested in how often primary care physicians take the sexual histories of patients during clinic visits. As part of the study, patients who attend a primary care clinic are asked to fill out a questionnaire immediately following a visit with their physician. Once the physicians become aware that their own behavior is being studied, which of the following is most likely to be a potential problem?