Exam 4: Biostatistics

For a case-control study designed to investigate a possible association between endometriosis and systemic lupus erythematosus (SLE), 1,040 women with SLE and 1,260 women without SLE are selected.  The investigators inquire about a history of endometriosis in both groups of women.  Among women with SLE, 240 had a history of endometriosis; among women without SLE, 210 had a history of endometriosis.  Which of the following is the estimated odds ratio of endometriosis in women with SLE compared to women without SLE?

A group of sports physicians plans to conduct a case-control study to investigate a possible association between adolescent idiopathic scoliosis (AIS) and sacroiliac joint (SIJ) dysfunction in young athletes.  The case group will consist of young athletes who were diagnosed with AIS during a regular checkup by a sports physician.  Which of the following is the most appropriate control group for this study?

The specificity of the standard test to detect disease X in the general population is 73%.  A team of researchers set forth a goal to increase specificity for detecting disease X.  They develop a new test and conduct a study to evaluate its performance on a random sample from the general population.  The results of their study are shown below. According to these results, have the researchers achieved their goal?

A study is conducted to describe the age-sex distribution of a certain country.  According to national data, the population pyramid of the country has the shape shown below. Based on the population pyramid, which of the following is most likely true about this country and its population?

A researcher is interested in assessing the blood folate level of women who live in a population with a high incidence of neural tube defects.  She takes a large random sample (n) of women age 18-45 and measures their blood folate levels.  The researcher finds that the data are normally distributed, and she reports the mean and standard deviation (SD) of the sample.  To account for sampling variation, she decides to calculate a 95% confidence interval to estimate the mean of the entire population.  The researcher concludes that 2.4 to 4.6 ng/mL might be a likely range for the true, unknown population mean.  Which of the following calculations was most likely used to compute this interval estimate of the population mean?

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?

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?

Researchers want to estimate the association between environmental lead exposure and cognitive deficits in children.  Among all children who received preventive care at 5 local pediatric clinics over the last 5 years, they identify 20 children diagnosed with cognitive deficits and 40 without the diagnosis.  The researchers then review the patients' medical records and calculate the distance between the patients' residence and known lead-contaminated geographic areas.  Which of the following best describes the study design used by the researchers?

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?

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 28-year-old woman comes to the office to establish care.  She recently moved to New York to begin a job as a copy editor at a major newspaper.  She has no known medical problems.  The patient is in a monogamous relationship with her husband.  She usually eats fast food for lunch, and she and her husband cook in the evenings.  She goes to the gym about once every 2 weeks.  The patient's temperature is 36.7 C (98 F), blood pressure is 118/64 mm Hg, pulse is 60/min, and respirations are 14/min.  Her BMI is 24.6 kg/m².  Physical examination is unremarkable.  Laboratory results are within the normal range.  Counseling this patient regarding diet and exercise habits would be an example of which of the following?

A novel serum biomarker, UWRLD99, is being evaluated for early detection of pancreatic cancer.  The concentration of UWRLD99 (measured in international units [IU] per dL) has been found to be elevated in patients with pancreatic adenocarcinoma.  Test results in 200 volunteers ("healthy") and 190 patients with biopsy-proven pancreatic cancer ("diseased") are given in the figure below.  The investigators determined the sensitivity and specificity of UWRLD99 for pancreatic cancer using a cutoff of 200 IU/dL (indicated by the solid vertical line). If they had instead used a lower cutoff as indicated by the dashed vertical line, which of the following would most likely be seen?

A meta-analysis of several trials on the effect of cocoa intake on systolic blood pressure (SBP) revealed the following results: All the trials evaluated the difference in SBP at 2 weeks.  Based on the data, which of the following is the most appropriate conclusion?

A group of psychiatrists conducts a double-blind placebo-controlled randomized trial to determine the efficacy and safety of cariprazine for the treatment of depressive episodes associated with bipolar I disorder (bipolar depression) in adults.  The treatment response rate was 46% for cariprazine versus 32% for placebo, and the rate for all adverse events was 7% for cariprazine versus 5% for placebo.  The differences in rates were statistically significant.  Which of the following is the approximate number of patients who must be exposed to cariprazine to cause harm to 1 person who otherwise would not have been harmed?

Researchers conduct a prospective study that demonstrates an association between alcohol consumption and transitional bladder carcinoma, with a relative risk (RR) of 1.81 and a p-value of 0.03.  They then divide the study subjects into 2 groups, smokers and non-smokers, and again examine the association between alcohol consumption and bladder cancer: The discrepancy between the overall results and the stratified results is best explained by which of the following?

A new serologic test has been developed for the detection of active pulmonary tuberculosis and is compared to the gold standard of sputum mycobacterial culture.  A total of 1000 subjects are randomly selected for testing from a population with a high prevalence of tuberculosis.  Results of the study are given below: Which of the following is the positive predictive value of the test under study?

A research group conducted a placebo-controlled clinical trial to assess whether a new drug to treat acute migraine with or without aura in adults is more effective than standard therapy.  A total of 3,500 patients with acute migraine were enrolled in the study and randomly assigned to either the new drug or standard treatment.  During the data analysis phase, the researchers decide to set alpha at 0.01 rather than 0.05.  Which of the following is the most likely result of this change?

A large cohort study is conducted to assess the association between smoking and squamous cell carcinoma of the esophagus among middle-aged Chinese men.  During 10 years of follow-up, smokers have 5 times the risk of esophageal carcinoma compared to non-smokers (relative risk = 5.0, 95% confidence interval = 2.9-7.1).  According to the study results, what percentage of squamous cell carcinoma of the esophagus in smokers can be attributed to smoking?

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 hospital wants to estimate the prevalence of diabetic nephropathy in the surrounding population of adults with type 2 diabetes.  Kidney biopsy samples are obtained from 500 adult patients with diabetes who receive care at the hospital.  The samples are then interpreted by 10 different pathologists, 5 of whom work at the hospital and 5 of whom work at nearby institutions.  A preliminary analysis shows that the pathologists who work for the hospital are 3 times more likely to interpret the biopsy samples as diabetic nephropathy compared to those who do not work for the hospital.  Which of the following most likely explains this difference in interpretation?