Statistics & Epidemiology Quiz

A 38-year-old primigravid woman comes to the physician's office at 20 weeks gestation for prenatal counseling. She is concerned about her baby's risk for Down syndrome and asks about measures to diagnose it early. The physician explains that triple screening may detect up to 60% of cases of chromosomal abnormalities and that amniocentesis may detect approximately 90% of cases. The patient decides not to undergo any testing. When explaining that amniocentesis detected a higher percentage of cases compared to triple screening, the physician was referring to which of the following values?

Gastric adenocarcinoma is typically diagnosed using upper endoscopy and managed with radical gastrectomy and, in some cases, chemoradiation; nevertheless, long-term survival is poor. Researchers in a region with a relatively high incidence of gastric adenocarcinoma are evaluating a novel screening test for early detection of the malignancy in high-risk patients. The novel test is based on the measurement of a recently discovered serologic marker of gastric adenocarcinoma, MGAc. Based on results of a large study sample of representative high-risk patients screened with MGAc and diagnosed with gastric adenocarcinoma, the mean survival of patients since time of diagnosis is 8.2 months. A review of records shows that, compared to these patients, similar high-risk patients who were diagnosed using the traditional endoscopic modality had a statistically significant lower mean survival of 7.1 months, with no statistically significant differences in the rates of radical gastrectomy or in the average number or intensity of chemoradiation cycles. Which of the following best explains these results?

A researcher wants to conduct a prospective cohort study to determine whether the use of tamoxifen as preventive treatment in premenopausal women at high risk for breast cancer is associated with mild cognitive impairment. The researcher plans to select premenopausal women newly identified to be at high risk for breast cancer who have no cognitive impairment and who recently started tamoxifen treatment. Item 1 of 2 Based on this information, which of the following should the researcher select for the comparison group?

A researcher wants to conduct a prospective cohort study to determine whether the use of tamoxifen as preventive treatment in premenopausal women at high risk for breast cancer is associated with mild cognitive impairment. The researcher plans to select premenopausal women newly identified to be at high risk for breast cancer who have no cognitive impairment and who recently started tamoxifen treatment. Item 2 of 2 The researcher plans to contact potential participants to explain the purpose of the study. All women who choose to participate in the study will be interviewed to collect information on demographics, general health, medical history, and baseline data. Which of the following should the researcher use to minimize the possibility of outcome misclassification in the study?

Researchers are interested in further investigating the side effects of a relatively recent hypolipidemic drug. A literature review showed several studies in which patients who took this drug reported severe acute myositis as an adverse event. In many instances, affected patients experienced life-threatening complications from myositis, including rhabdomyolysis leading to acute renal failure and profound electrolyte abnormalities. However, none of these studies documented a statistically significant difference in the occurrence of severe acute myositis between the treatment and placebo groups. Which of the following is the best method to further investigate the association between use of this hypolipidemic drug and development of severe acute myositis?

A randomized, parallel-group, controlled clinical trial evaluates the effectiveness of an anti-inflammatory intervention as treatment for neuropathic pain following spinal cord injury. Participants with varying levels and severities of spinal cord injury are randomly assigned to either a 24-week, anti-inflammatory diet treatment group or a control group. Primary outcomes consist of changes in pain scores and markers of inflammation at 6 months. Preliminary analyses reveal a significant reduction in pain scores in the treatment group from baseline to 6 months (p = 0.03). There was a significant reduction in pain scores among nonobese subjects (p = 0.01) and a nonsignificant increase in pain scores among obese subjects (p = 0.06). Which of the following is the best explanation for these differences in findings between obese and nonobese subjects?

Researchers are designing a study to compare the efficacy and safety of a new selective inhibitor of dipeptidyl peptidase 4 (DPP-4) to placebo in 3,850 patients with type 2 diabetes mellitus (T2DM) and recent acute coronary syndrome. Potential participants will be assigned to receive the new inhibitor or placebo in addition to standard-of-care treatment for T2DM. Throughout the study, patients will also receive treatment for cardiovascular risk factors according to standardized guidelines. The researchers believe that the efficacy of the new inhibitor may be different at different levels of baseline renal function. Based on this information, which of the following is most appropriate to determine whether the researchers' belief is correct?

A cohort of patients with myotonic dystrophy was retrospectively analyzed from 1993 to 2010 to identify incident cases of cancer. The researchers identified 2 cases of thyroid cancer and reported a standardized incidence ratio of 7.4 (P-value = 0.02). This ratio was derived using which of the following formulas?