Deck 4: Biostatistics

Question 1

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)Between 0 and 1
B)1
C)Between 1 and 2
D)2
E)Between 2 and 3

Answer 1

A
This bar graph illustrates the frequency of urinary tract infection (UTI) episodes in the sample.  According to the figure, 50 children had 0 UTIs, 30 children had 1 UTI, 10 had 2 UTIs, and 10 had 3 UTIs.
In general, the average (or mean) of a dataset is the sum of the values divided by the total number of values.  In this example, the average number of UTI episodes per child is the sum (ie, total number) of UTIs divided by the total sample size (ie, total number of children).  The total sample size is: 50 + 30 + 10 + 10 = 100 children.  The total number of UTIs is: (0 × 50) + (1 × 30) + (2 × 10) + (3 × 10) = 0 + 30 + 20 + 30 = 80 UTIs.  The average is obtained by dividing the total number of UTIs (80) by the total sample size (100).  Therefore, the average number of UTI episodes per year = 80/100 = 0.8 UTIs for a child in this sample.
In conclusion, children age 2-5 years in this clinic experienced between 0 and 1 UTI over 1 year on average.
Educational objective:
The average (or mean) of a dataset of values is the sum of the values divided by the total number of values.

Question 2

A research group is studying the correlation between BMI and blood pressure in a random sample of children age 12-16.  After collecting data, they conduct a correlation analysis at a 1% significance level.  The researchers find that BMI correlates with systolic blood pressure with a coefficient of r = 0.46 (p <0.001) and diastolic blood pressure with a coefficient of r = 0.37 (p <0.001).  Which of the following is the most accurate interpretation of these results?

A)An increase in BMI causes a statistically significant increase in blood pressure in children
B)Childhood obesity significantly increases the risk of cardiovascular disease later in life
C)There is a statistically significant negative linear relationship between BMI and blood pressure in children
D)There is a statistically significant positive linear relationship between BMI and blood pressure in children
E)There is no statistically significant linear relationship between BMI and blood pressure in children

Answer 2

D

The correlation coefficient (r) measures the direction and strength of a linear relationship (ie, association) between 2 variables (that are usually quantitative).
Direction:  When r <0, the linear relationship is negative and one variable increases as the other decreases; when r >0, the linear relationship is positive and both variables increase and decrease together.
Strength:  When r values are close to −1 or 1, the linear relationship is strong; when r values are close to 0, the linear relationship is weak.
A correlation analysis evaluates whether a linear relationship exists between 2 variables.  A p-value less than a given significance level indicates that there is a statistically significant linear relationship between the variables.  However, a statistically significant linear relationship result does not imply that the relationship is causal (correlation ≠ causation) because when 2 variables are correlated, it does not necessarily mean that one is directly causing the other to change (Choices A and B).
In this study, researchers studied the correlation between BMI and blood pressure in a random sample of children.  Study results showed that the correlation coefficients for BMI and systolic/diastolic blood pressure are both positive (r = 0.46 and r = 0.37, respectively, are both >0); therefore, there is a positive linear relationship between BMI and blood pressure (Choice C).  Because the p-value for both coefficients (p <0.001) is less than 0.01 (the given significance level of 1%), the linear relationship is statistically significant (Choice E).
Educational objective:
The correlation coefficient (r) indicates whether there is a negative (r <0) or positive (r >0) linear relationship between 2 variables.  The closer r is to −1 or +1, the stronger the linear relationship.  A statistically significant (ie, p-value < significance level) linear relationship between 2 variables does not imply that the relationship is causal.

Question 3

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?

A)Berkson's bias
B)Hawthorne effect
C)Lead-time bias
D)Pygmalion effect
E)Recall bias

Answer 3

B
The Hawthorne effect (observer effect) is the tendency of study subjects to change their behavior as a result of their awareness that they are being studied.  This can impact the observed outcomes, thereby seriously affecting the validity of the study.  The Hawthorne effect is commonly seen in studies concerning behavioral outcomes or outcomes that can be influenced by behavioral changes.  In this example, physicians (not patients) are the subjects of the study; those physicians who are aware that they are being studied may modify their behavior and start taking sexual histories.  To minimize the Hawthorne effect, study subjects can be kept unaware that they are being studied, but this can occasionally pose ethical problems.
(Choice A)  Berkson's bias refers to selection bias created by choosing hospitalized patients as the control group.
(Choice C)  Lead-time bias refers to the apparent prolongation of survival after applying a screening test that detects a disease earlier than it would have been otherwise detected but without any real effect on prognosis.
(Choice D)  Pygmalion effect describes the fact that a researcher's beliefs in the efficacy of treatment can potentially affect the outcome.  In the classic classroom experiment that first described the Pygmalion effect, a group of students were randomly assigned high intelligence quotient (IQ) scores; their teachers were then told of these artificial results and had higher expectations of this group as a result.  The students with the randomly assigned high IQ scores actually performed better, likely because their teachers unconsciously behaved in a manner that would facilitate their success.
(Choice E)  Recall bias results from inaccurate recall of past exposures by patients.  Although recall bias is possible whenever questionnaires are administered, it is unlikely in this case as the patients fill out a form immediately upon leaving the doctor's office.
Educational objective:
The Hawthorne effect (observer effect) is the tendency of study subjects to change their behavior as a result of their awareness that they are being studied.

Question 4

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)Beta error
B)Recall bias
C)Observer bias
D)Effect modification
E)Selection bias

Question 5

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)Ascertainment bias
B)Confounding
C)Observer bias
D)Recall bias
E)Selection bias

Question 6

A group of researchers conducted a case-control study to estimate the association between exposure to a certain pesticide and head and neck squamous cell carcinomas.  Controls were matched to cases by age and gender.  Exposure status was determined by interviewing the subjects.  On matched-pair analysis, the odds ratio is 7.5 (95% confidence interval: 2.3-14.8).  Based on this information, which of the following is most likely to affect the validity of this study?

A)Confounding bias by age
B)Healthy worker bias
C)Misclassification bias
D)Nonresponse bias
E)Placebo effect

Question 7

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?

A)High accuracy; high precision
B)High accuracy; low precision
C)High sensitivity; low specificity
D)Low accuracy; high precision
E)Low accuracy; low precision
F)Low sensitivity; high specificity

Question 8

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)+0.8
B)+0.2
C)0
D)−0.2
E)−0.8

Question 9

A 65-year-old man with a history of congestive heart failure is hospitalized with chest pain and hypotension requiring admission to the cardiac care unit.  An intra-arterial line is placed for direct blood pressure monitoring.  Consecutive readings of his intra-arterial blood pressure are 75, 110, 80, 90, 75, and 110 mm Hg.  Which of the following represents the median of these blood pressure readings?

A)80 mm Hg
B)85 mm Hg
C)90 mm Hg
D)100 mm Hg
E)110 mm Hg

Question 10

A surveillance study is conducted to assess the efficacy and safety of tolvaptan, a drug currently being used in the clinical setting for treating heart failure with volume overload.  The study enrolls 8,300 patients with a variety of medical comorbidities who received tolvaptan once daily in the morning for 2 weeks.  Results showed that tolvaptan demonstrated aquaretic efficacy in patients with diuretic-resistant volume overload, but that hypernatremia was a complication in a small number of patients.  Researchers recommended a lower dose of tolvaptan in those with normonatremia and hypokalemia to prevent hypernatremia.  Which of the following best describes this type of study?

A)Preclinical study
B)Phase I clinical trial
C)Phase II clinical trial
D)Phase III clinical trial
E)Phase IV clinical trial

Question 11

A large prospective study evaluates the relationship between alcohol consumption and breast cancer.  A total of 4000 middle-aged women are enrolled in the study through a random selection of residential addresses.  Daily alcohol consumption and breast cancer incidence are assessed through the use of periodic questionnaires.  On five-year follow-up, the investigators report the association between alcohol consumption and breast cancer as a relative risk of 1.32 (95% confidence interval = 0.90-1.85); 800 subjects were lost to follow-up by the end of the study, the majority of whom were moderate to heavy alcohol consumers.  According to this information, which of the following biases is most likely to be present and may have affected the results?

A)Lead-time bias
B)Observer bias
C)Random misclassification bias
D)Recall bias
E)Selection bias

Question 12

A geneticist is interested in the potential causes of a congenital abnormality.  She hypothesizes that acetaminophen use during the first trimester of pregnancy might be associated with the abnormality.  In her study, a sample of mothers of children with and without the abnormality are randomly selected from government birth records.  Personal interviews are then conducted with the mothers to determine fetal exposure to acetaminophen.  Results show that mothers of children who do not have the abnormality did not take acetaminophen as frequently during the first trimester.  This type of study is most susceptible to which of the following types of bias?

A)Allocation bias
B)Detection bias
C)Recall bias
D)Referral bias
E)Selection bias

Question 13

A group of researchers conduct a study to evaluate the pharmacologic properties of oxfendazole, an anthelminthic agent.  As part of the study, increasing oral doses of oxfendazole (0.5 to 60 mg/kg) are administered to healthy volunteers.  Data is collected to form a pharmacokinetic profile of the drug and its metabolites, and the incidence of adverse effects is recorded for the various dosages.  A total of 20 healthy male and female (nonchildbearing potential) volunteers participate in the study.  Oxfendazole is found to be well tolerated throughout the dose range without any serious adverse effects or deaths.  Which of the following best describes this type of study?

A)Preclinical study
B)Phase I clinical trial
C)Phase II clinical trial
D)Phase III clinical trial
E)Phase IV clinical trial

Question 14

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?

A)Confounding
B)Effect modification
C)Latent period
D)Observer bias
E)Selection bias

Question 15

An epidemiologist wants to conduct a study on hepatitis C (HCV) transmission in a country with limited healthcare resources.  She has access to a cohort of adults newly diagnosed with HCV and a cohort of age-matched HCV-negative adults.  She plans to use these 2 cohorts of adults to conduct a case-control study.  Which of the following would be the most appropriate measure of interest for this researcher's study?

A)The average death rate in each cohort
B)The frequency of past blood transfusions in each cohort
C)The incidence rate of liver cancer in HCV-positive participants
D)The rate of eventual HCV infection in HCV-negative participants
E)The rate of treatment-related adverse effects in HCV-positive participants

Question 16

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)Confounding
B)Effect modification
C)Measurement bias
D)Meta-analysis
E)Observer bias
F)Recall bias

Question 17

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?

A)Mean
B)Mode
C)Range
D)Standard deviation
E)Variance

Question 18

A new biomarker has been shown to allow for the early detection of non-small cell lung carcinoma.  A preliminary analysis on a cohort study of this new test demonstrates that its use prolongs survival of lung cancer patients by 3 months when compared to the survival of patients diagnosed by conventional methods.  A secondary analysis reveals no difference in 6-month mortality rates between the 2 groups.  Which of the following factors most likely explains the study results?

A)Confounding
B)Lead-time bias
C)Length-time bias
D)Measurement bias
E)Observer bias
F)Rare disease assumption

Question 19

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?

A)Confounding
B)Lead-time bias
C)Observer bias
D)Recall bias
E)Selection bias

Question 20

A study is conducted to assess the potential clinical benefit and treatment-related toxicities of tandutinib in combination with bevacizumab for patients with recurrent glioblastoma.  Forty-one recurrent, bevacizumab-naïve glioblastoma patients were recruited for the study.  Treatment consisted of tandutinib 500 mg twice daily and bevacizumab 10 mg/kg every 2 weeks starting day 15.  Study results showed that all patients suffered treatment-related toxicities; common grade ≥3 toxicities were hypertension (17.1%), muscle weakness (17.1%), lymphopenia (14.6%), and hypophosphatemia (9.8%).  Researchers then compared the data with results from previous clinical trials assessing the clinical benefit of bevacizumab monotherapy.  They concluded that tandutinib with bevacizumab was as effective but more toxic than bevacizumab monotherapy.  Which of the following best describes this type of study?

A)Preclinical study
B)Phase I clinical trial
C)Phase II clinical trial
D)Phase III clinical trial
E)Phase IV clinical trial

Question 21

A medical student is conducting a chart review of patients admitted to the local emergency department with acute pancreatitis.  He is interested in comparing blood glucose levels between mild and severe cases.  Before attempting to compare the mean blood glucose levels between the 2 groups of patients, he decides to conduct a descriptive analysis of the variables in each group.  Blood glucose levels in patients with severe acute pancreatitis were found to have a strong positively skewed distribution.  Which of the following is most likely to be true regarding the data for the severe acute pancreatitis group?

A)The mean is equal to the median
B)The mean is equal to the mode
C)The mean is greater than the median
D)The median is greater than the mean
E)The mode is greater than the mean

Question 22

A physician research group is evaluating the efficacy of a new lipid-lowering drug, Superstatin, which is being marketed directly to consumers as a groundbreaking new therapy to prevent heart attacks.  The drug manufacturer claims that the drug is more effective than existing hypolipidemic agents for primary prevention of myocardial infarction.  Results of a 5-year, randomized, double-blinded, controlled study to evaluate the efficacy of Superstatin are shown below. Compared to the control medication, how many patients need to be treated with Superstatin to prevent one additional myocardial infarction?

A)2
B)5
C)23
D)48
E)67
F)92
G)100

Question 23

Blood pressure measurements are obtained from a sample of individuals with no known medical conditions.  For systolic blood pressure (SBP), the mean measurements and associated standard deviations (SDs) are shown by age group for men and women: If hypertension is defined as SBP >140 mm Hg, approximately what percentage of men age 35-44 in this sample will be classified as having hypertension, assuming a normal (Gaussian) distribution?

A)16%
B)34%
C)50%
D)68%
E)84%
F)95%

Question 24

A group of researchers wants to identify factors related to hospital-acquired bacteremia caused by methicillin-resistant Staphylococcus aureus (MRSA).  A total of 45 patients were enrolled in the study after MRSA was isolated from a blood sample taken from them on the third or subsequent day after admission.  In addition, 90 patients admitted to the hospital over the same period with a length of stay >2 days who did not have bacteremia were randomly selected.  The frequency of factors such as insertion of a central line or urinary catheter and surgical site infection were then compared between the 2 groups.  Which of the following is the most appropriate null hypothesis for this study?

A)Hazard ratio is equal to 1
B)Hazard ratio is not equal to 1
C)Odds ratio is equal to 1
D)Odds ratio is not equal to 1
E)Relative risk is equal to 1
F)Relative risk is not equal to 1

Question 25

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?

A)Drugs A and B require treating the same number of children to prevent 1 additional death, so they are equally effective
B)Drug A requires treating fewer children to prevent 1 additional death compared to Drug B, so Drug A is less effective than Drug B
C)Drug A requires treating fewer children to prevent 1 additional death compared to Drug B, so Drug A is more effective than Drug B
D)Drug A requires treating more children to prevent 1 additional death compared to Drug B, so Drug A is less effective than Drug B
E)Drug A requires treating more children to prevent 1 additional death compared to Drug B, so Drug A is more effective than Drug B

Question 26

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)Median survival
B)Odds ratio
C)Prevalence ratio
D)Relative rate
E)Relative risk

Question 27

A residency program organized a barbecue at the beginning of the academic year to welcome the new class of first-year residents.  The total number of attendees was 100, including faculty, administrative staff, and residents.  Hamburgers, hotdogs, and potato salad were served.  The following day, 28 of the attendees had diarrhea and vomiting.  All of the attendees were questioned about what they had eaten, and the following table was obtained: Which of the following best describes the attack rate among all of the attendees who had potato salad?

A)8%
B)11%
C)13%
D)20%
E)28%
F)30%
G)34%
H)47%

Question 28

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)Any significant findings will be reported with greater confidence
B)There will be a higher probability of a type I error
C)There will be a higher probability of finding statistically significant results
D)There will be a lower probability of a type II error
E)The study will have more statistical power

Question 29

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)2
B)25
C)40
D)72
E)94

Question 30

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)A higher mean SBP was seen in the cocoa groups overall
B)Cocoa intake should be recommended for blood pressure management
C)Cocoa intake was associated with a statistically significant decrease in SBP
D)Studies 2, 6, and 7 showed a statistically significant increase in SBP
E)There was no statistically significant change in SBP overall

Question 31

A suburban hospital is undergoing an annual review by a health care accreditation organization.  As part of the process, iatrogenic infection rates are assessed for all major hospital services.  Inpatient surgical infection statistics for the last year are shown below. What is the case-fatality rate for methicillin-resistant S aureus surgical infections in this hospital?

A)40/70
B)40/110
C)40/75
D)53/100
E)70/220

Question 32

A study assessed the association between a new vaccine and traveler's diarrhea (TD).  Researchers selected a random sample of people who intended to travel to regions where they were at increased risk for TD and who had received the new vaccine and another independent random sample of people who intended to travel to the same regions and who had not received the new vaccine.  These 2 samples of travelers were assessed for the occurrence of TD during the trip and for 7 days after returning home.  Which of the following measures of association are the investigators most likely to report?

A)Incidence
B)Median survival time
C)Odds ratio
D)Prevalence
E)Relative risk

Question 33

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)(20 × 30) / (70 × 40)
B)(20 × 40) / (70 × 30)
C)(20 × 70) / (30 × 40)
D)(20 / 50) / (70 / 110)
E)(20 / 90) / (30 / 70)

Question 34

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)3)5 and 6.0 ng/mL
B)3)5 and 6.5 ng/mL
C)4)0 and 6.0 ng/mL
D)4)0 and 5.5 ng/mL
E)4)5 and 5.5 ng/mL

Question 35

The aim of a case-control study is to investigate the association between probiotic yogurt intake before and during pregnancy and gestational diabetes mellitus (GDM) in women age >18 during their 24 to 28 weeks of a singleton pregnancy.  The investigators obtain a history of probiotic yogurt intake between cases and controls.  Results of the study are shown below. Which of the following best represents the odds of high probiotic yogurt intake in women with GDM compared to women without GDM?

A)0)17
B)0)45
C)0)66
D)1)51
E)2)20

Question 36

A study was conducted to assess the age at menarche among young female gymnasts.  Based on commitment to the sport, gymnasts were divided into two groups: competitive gymnasts and recreational gymnasts. Assuming that age at menarche is normally distributed, which of the following is closest to the probability that a randomly chosen competitive gymnast will have onset of menarche at age ≥16?

A)0)997
B)0)950
C)0)680
D)0)160
E)0)025
F)0)0015

Question 37

A study is conducted to assess the effectiveness of a new medication X added to standard antihypertensive therapy compared to standard antihypertensive therapy alone for preventing the development of proteinuria in patients recently diagnosed with essential hypertension.  Five years after diagnosis, 97 of 100 patients on the medication X + standard antihypertensive therapy regimen have not developed proteinuria, and 90 of 100 patients on a standard antihypertensive therapy regimen have not developed proteinuria.  According to these results, which of the following represents the approximate number of patients with essential hypertension who need to be treated with medication X to prevent an additional patient from developing proteinuria within 5 years?

A)3
B)7
C)10
D)15
E)70

Question 38

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?

A)2
B)8
C)14
D)21
E)50

Question 39

Researchers conducted a randomized controlled trial to assess the effectiveness of a new drug to reduce severe cutaneous reactions in patients with rheumatoid arthritis who are treated with adalimumab.  Of 150 adults with rheumatoid arthritis who are treated with adalimumab, 75 received the new drug in addition to adalimumab, and 75 received a placebo in addition to adalimumab.  Results show that 6 patients in the new drug group developed severe cutaneous reactions, compared to 9 in the placebo group.  Which of the following represents the relative risk reduction for severe cutaneous reactions among patients in the new drug group?

A)0)08
B)0)10
C)0)12
D)0)33
E)0)67

Question 40

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)2
B)10
C)20
D)64
E)128

Question 41

The population pyramid of a certain country is shown below. Based on the diagram, which of the following best characterizes this population?

A)High mortality rate
B)Long life expectancy
C)Low birth rate
D)Shrinking population
E)Stable population

Question 42

A study is conducted to estimate the prevalence of catheter-associated urinary tract infection (CAUTI) in the intensive care unit (ICU) of an urban hospital.  The plot below shows the number of cases of CAUTI in this hospital during the month of July among patients in the ICU.  Based on the plot, which of the following is the number of prevalent cases on July 31?

A)1
B)4
C)5
D)8
E)9

Question 43

A research laboratory develops a new serologic test for detecting prostate cancer.  The new assay is compared to transrectal ultrasound-guided prostate biopsy to determine sensitivity and specificity parameters.  It is found that the test result is negative in 95% of patients who do not have the disease.  If the new assay is used on 8 blood samples taken from patients without prostate cancer, what is the probability of all 8 test results coming back negative?

A)0)05 × 8
B)0)95 × 8
C)0)05⁸
D)0)95⁸
E)1 − 0.05⁸
F)1 − 0.95⁸

Question 44

A genome-wide association study (GWAS) of rheumatoid arthritis (RA) is performed in a cohort of Portuguese patients, including 907 cases with RA and 1,524 controls without RA.  Logistic regression is used to test the association between RA and hundreds of thousands of loci.  These association results are then compared with data from a European GWAS cohort of 4,036 patients with RA and 6,959 patients without RA.  Finally, the Portuguese and European study results are combined into a meta-analysis.  Based on these data, the investigators identify 3 new loci that are associated with RA based on a significance level threshold of 5 × 10⁻⁸: Previous studies had identified 30 loci that accounted for <35% of disease heritability for RA.  Which of the following statements is correct regarding this study?

A)Combining the results of the European and Portuguese studies into a meta-analysis decreases the power
B)Logistic regression is used because there is a stepwise increase in the strength of association from Locus 1 to Locus 3
C)The association between Locus 1 and RA in the meta-analysis is not statistically significant because the odds ratio is <1
D)The threshold used for the p-value in the meta-analysis is 5 × 10⁻⁸ because of the large number of loci studied
E)With this meta-analysis, the 33 identified loci account for most disease heritability in RA

Question 45

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)Higher number of false negatives
B)Higher positive predictive value
C)Higher sensitivity
D)Lower number of false positives
E)Lower number of true positives

Question 46

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)0)1
B)0)7
C)0)8
D)1)2
E)1)5

Question 47

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)Case finding
B)Cognitive-behavioral therapy
C)Community-level intervention
D)Health promotion
E)Health risk assessment
F)Precontemplative stage intervention
G)Tertiary prevention

Question 48

A 62-year-old man with diabetes, hypertension, and hyperlipidemia comes to the emergency department of an academic medical center with chest pain, nausea, vomiting, and diaphoresis.  An electrocardiogram demonstrates ST elevation in the anterior leads, and cardiac enzymes are markedly elevated.  Investigators at the center are designing a randomized control trial to test the hypothesis that drug B will decrease the mortality associated with acute ST-elevation myocardial infarction compared to standard of care.  To ensure that investigators will not miss a difference between drug B and standard of care (if a difference truly exists), which of the following would they want to maximize?

A)α
B)β
C)Type I error
D)Type II error
E)1 - β

Question 49

In a reference sample of hundreds of healthy subjects, the laboratory reference range for a novel marker of cardiac injury is 0.04-0.08 U/mL at the standard 95% level of probability.  The marker has very high sensitivity and specificity for myocardial tissue.  The clinical cardiology team would like to use a 99.7% reference range to assess patients who come to the emergency department with chest pain and have a high pretest probability of cardiac ischemia.  An elevated value of the marker is defined as exceeding the 99.7th percentile of the reference sample.  Assuming a normal (Gaussian) distribution with a mean of 0.06 U/mL, which of the following most closely approximates the corresponding reference range?

A)0)03 to 0.09
B)0)035 to 0.085
C)0)045 to 0.075
D)0)05 to 0.07
E)0)055 to 0.065

Question 50

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)Berkson's bias
B)Placebo effect
C)Poor blinding
D)Researcher expectancy
E)Sample size

Question 51

A group of psychiatrists has noticed an unusual number of older individuals with depression in the surrounding community.  A decision is taken to conduct a cross-sectional study to estimate the prevalence of depression in this specific population.  Estimates for the prevalence of depression (cases per 100 individuals) in the community are as follows: Suppose during an afternoon clinic, a psychiatrist sees a 65-year-old woman, a 72-year-old man, and an 84-year-old woman from this community.  Assuming no relation between the 3 patients, what is the probability that none of them has depression?

A)0)001
B)0)011
C)0)295
D)0)705
E)0)999

Question 52

Results of a recent study on the association between levels of glycosylated hemoglobin (HbA1c) and levels of high-sensitivity C-reactive protein (hs-CRP) in patients with type II diabetes mellitus (T2DM) read as follows:"The results of our study show that levels of HbA1c positively correlated with the levels of hs-CRP (r = 0.80).  The probability that these results were due to chance alone is 3%, with a 10% chance of concluding no relationship between HbA1c and hs-CRP when one truly exists."Based on this information, which of the following most likely represents the p-value and the power of the correlation test in the study?

Question 53

A physician is conducting a double-blind randomized controlled trial to determine the effect of a new cream in reducing the risk of relapse in chronic recurrent atopic dermatitis.  A total of 30 patients with moderate to severe atopic dermatitis who were experiencing a flare are randomly divided into 2 groups: 15 patients will receive the new cream, and 15 patients will receive emollient alone.  The rate of relapse after 2 weeks of treatment is 25% in the group who received the new cream and 50% in the group who received emollient alone.  However, the difference is found to be not statistically significant (p = 0.14).  The physician concludes that use of the new cream does not reduce the risk of relapse in chronic recurrent atopic dermatitis.  Which of the following is most likely to explain the results of the study?

A)Ascertainment bias
B)Confounding bias
C)Ecologic fallacy
D)Insufficient statistical power
E)Recall bias

Question 54

A study examined the effect of a low-carbohydrate diet compared to a low-fat diet on body weight.  A sample of 150 overweight but otherwise healthy adults from a large city was enrolled in the study and randomly assigned in a 1:1 ratio to either the low-carbohydrate (40 g/d) or the low-fat (<7% saturated fat) diet.  At 12 months, a greater body weight change was reported in the low-carbohydrate diet group compared to the low-fat diet group, with a mean difference in body weight change of −3.5 kg (p = 0.01, predetermined significance level = 0.05).  Which of the following is the most accurate interpretation of the results of this study?

A)The observed mean difference in body weight change of −3.5 kg is not statistically significant
B)The probability of observing a mean difference in body weight change of −3.5 kg is 0.01
C)There is a 1% chance of observing a mean difference in body weight change of at least −3.5 kg when no difference between groups is assumed
D)There is a 1% chance that an adult on a low-carbohydrate diet will have a body weight change of at least −3.5 kg at 12 months after starting the diet
E)There is a 1% chance that the mean difference in body weight change is biased in favor of the low-carbohydrate diet group

Question 55

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)Mean ± 1.96 × SD
B)Mean ± 1.96 × (SD/√n)
C)Mean ± 2.58 × SD
D)Mean ± 2.58 × (SD/√n)
E)Mean ± (SD/n)

Question 56

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)The country seems to have high birth rates; therefore, the population must be growing
B)The country seems to have a high death rate; therefore, the population must be shrinking
C)The country seems to have a low birth rate; therefore, the population must be old
D)The country seems to have a short life expectancy; therefore, the population must be young
E)The country seems to have a similar percentage of people in each age cohort; therefore, the population must be stable

Question 57

The population pyramid of all races and ethnicities for a certain state in the United States is shown below. Which of the following statements best describes the population of this specific state?

A)Life expectancy is low due to its high mortality rate
B)The high birth rate indicates the population is growing
C)The population is shrinking due to the migration of older people
D)The similar number of people in each age cohort indicates the population is stable
E)The state has a young population because of its high birth rate

Question 58

A study determines that the mean blood cholesterol level is 195 mg/dL in 200 non-diabetic hospitalized patients and 210 mg/dL in 180 diabetic hospitalized patients.  The probability that the observed difference is due to chance alone is reported to be 5%.  There is also a 20% probability of concluding that there is no difference in blood cholesterol level when there is one in reality.  What is the power of the study?

A)0)05
B)0)20
C)0)50
D)0)80
E)0)95

Question 59

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?

A)1,000 / 4,000,000
B)6,000 / 3,980,000
C)6,000 / 4,000,000
D)7,000 / 3,980,000
E)7,000 / 4,000,000
F)26,000 / 3,959,000
G)41,000 / 4,000,000

Question 60

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?

A)0)03
B)0)06
C)0)09
D)0)11
E)0)20

Question 61

A study is conducted to assess whether quantitative measurement of heat shock protein 90 alpha (Hsp90α) in plasma can improve diagnostic accuracy and help monitor treatment response in liver cancer patients.  A total of 300 individuals (100 liver cancer patients and 200 healthy controls) participate in the study.  Analyses reveal that 90 of the liver cancer patients have an abnormally high plasma Hsp90α level and that 12 of the healthy controls have an abnormally high plasma Hsp90α level.  An abnormally high plasma Hsp90α level indicates a positive test for liver cancer.  Which of the following values best represents the specificity of this test?

A)6%
B)10%
C)33%
D)90%
E)94%

Question 62

A randomized controlled trial is conducted to compare transcatheter aortic valve replacement (TAVR), using a self-expanding transcatheter aortic valve bioprosthesis, with surgical aortic valve replacement in patients with severe aortic stenosis.  The objective is to determine the difference in risk of death from any cause.  Seven hundred forty-seven patients with severe aortic stenosis who are at increased surgical risk are recruited and randomly assigned to groups for treatment with TAVR or surgical valve replacement.  Follow-up assessments are performed at discharge and at 1 month, 6 months, and 1 year.  The 1-year follow-up results are as follows: Which of the following best represents the absolute risk reduction for death from any cause in patients treated with TAVR compared to those treated with surgical replacement?

A)(68/357) − (57/390) = 0.044
B)[(68/357) − (57/390)] / (68/357) = 0.233
C)(57/390) / (68/357) = 0.767
D)(68/357) / (57/390) = 1.303
E)1 / [(68/357) − (57/390)] = 22.562

Question 63

The graph below shows the yearly incidence of viral hepatitis per 100,000 population from 1982-2012 in the United States (US). During this period, the total population in the US continued to increase, as shown in the table below: At any given time point, the number of individuals at risk for hepatitis infection is assumed to be equal to the total US population.  Based on these data, which of the following is most likely to be true?

A)After 2006, hepatitis B prevalence surpassed hepatitis A and hepatitis C prevalence
B)In 1987, there were as many individuals with hepatitis A as with hepatitis B in the US
C)In 1989, there were more individuals with hepatitis A than with hepatitis B in the US
D)In 1997, there were more new cases of hepatitis A than of hepatitis B and C combined
E)The number of new cases of hepatitis A diagnosed in 1982 and 1998 were exactly the same

Question 64

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?

A)1
B)2
C)3
D)4
E)5

Question 65

A prospective study evaluates the relationship between regular antioxidant supplement use (vitamins C and E) and the risk of stroke in healthy and physically active men age 40-60.  The study compares the risk of stroke among men who consumed antioxidant supplements for ≥5 years and among men who consumed antioxidant supplements for <5 years, as compared to a reference group of men who never consumed antioxidant supplements.  According to the study results, men who consumed antioxidant supplements for <5 years and men who consumed antioxidant supplements for ≥5 years have stroke relative risks of 0.95 (p = 0.45) and 0.75 (p < 0.01), respectively, when compared to the reference group.  The results of the study were adjusted to account for baseline differences related to healthy behaviors and overall health.  Which of the following factors most likely explains why the relative risk of stroke is lower with longer antioxidant use?

A)Accumulation effect
B)Lead-time bias
C)Observer bias
D)Rare disease assumption
E)Selection bias

Question 66

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?

A)50
B)80
C)120
D)150
E)400

Question 67

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)2)8%
B)3)2%
C)3)6%
D)4)8%
E)5)2%

Question 68

Carbamoyl phosphate synthetase I deficiency is an inherited disorder characterized by accumulation of ammonia in the blood.  The most severe form occurs in the first 24-72 hours following birth, after feeding begins and milk proteins start to be broken down in the liver.  If left untreated, affected neonates often die due to severe metabolic derangements; survivors often develop permanent neurologic injury.  The estimated incidence of carbamoyl phosphate synthetase I deficiency is about 1 in 800,000 newborns.  If a decision is made to test all newborns for this disease, then this initial test should be designed to have a high:

A)Cutoff value
B)Number of true negatives
C)Positive predictive value
D)Sensitivity
E)Specificity

Question 69

An investigator is conducting a randomized, double-blind, placebo-controlled clinical trial of a new drug for the treatment of peripheral neuropathy in adults with multiple myeloma (MM).  One hundred fifty patients with MM are enrolled in the trial and randomized to receive either the new drug (n = 75) or placebo (n = 75).  Trial protocol requires that patients in both groups take 1 pill per day and keep a pain diary.  After 3 months of treatment, each patient is interviewed, and the pain diaries are reviewed; 9 patients taking the new drug and 3 patients taking placebo did not take the pills as instructed.  The investigator decides to conduct an intention-to-treat analysis of the study data.  Which of the following best describes how the data pertaining to all patients who did not adhere to protocol should be treated?

A)Conduct separate analyses of the 12 nonadherent patients and the 138 adherent patients
B)Exclude all 12 nonadherent patients from analysis
C)Exclude the 3 nonadherent patients in the group taking placebo from analysis
D)Exclude the 9 nonadherent patients in the group taking the new drug from analysis
E)Keep all 12 nonadherent patients in their respective groups for analysis

Question 70

The prevalence of a chronic disease that affects mostly older individuals has been constant in a population for the last 15 years.  As a result of worsening economic conditions that have no effect on the disease itself, many young healthy individuals emigrate from the population.  Which of the following is the most likely effect of the emigration on the estimate of disease prevalence over the next few years?

A)The prevalence would decrease
B)The prevalence would increase
C)The prevalence would remain the same
D)It is not possible to determine the effect on prevalence from the information given

Question 71

A research laboratory is evaluating a new dipstick test for diagnosing urinary tract infections (UTIs).  The new test is compared to urinalysis of a midstream urine specimen (considered the diagnostic gold standard) to establish diagnostic test parameters.  The study enrolls 300 patients, of which 100 have a UTI as determined by urinalysis.  The new dipstick test is determined to be 70% sensitive and 90% specific for the diagnosis of UTIs.  How many false positives are present in the study?

A)20
B)30
C)70
D)120
E)180

Question 72

A new tumor marker is being investigated for its usefulness in diagnosing ovarian cancer.  A sample of 400 women is stratified into 2 groups based on the presence or absence of BRCA mutations.  Serum levels of the new marker are obtained in the 2 groups; in addition, both groups of women undergo conventional screening to determine their disease status.  The curves on the top represent the distribution of the new serum marker in women with BRCA mutations, and the curves on the bottom represent the distribution of the new serum marker in women without the BRCA mutations. The proposed serum marker cutoff value for both populations is shown.  Use of the new serum marker in women with BRCA mutations, compared with those without BRCA mutations, is associated with which of the following?

A)Higher sensitivity and higher specificity
B)Higher sensitivity and lower specificity
C)Higher sensitivity and same specificity
D)Lower sensitivity and higher specificity
E)Lower sensitivity and lower specificity
F)Lower sensitivity and unchanged specificity
G)Unchanged sensitivity and unchanged specificity

Question 73

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?

A)0)19
B)0)23
C)0)27
D)0)30
E)0)40

Question 74

A study evaluated the role of angiotensin-converting enzyme (ACE) inhibitors in the prevention of coronary events in patients with diabetes.  During 5 years of follow-up, 120 out of 400 diabetic patients who had taken an ACE inhibitor developed an acute coronary event.  Over the same time, 100 out of 300 diabetic patients who had not taken an ACE inhibitor experienced coronary events.  What was the relative risk of developing a coronary event in diabetic patients who were taking ACE inhibitors compared to diabetic patients who were not taking ACE inhibitors?

A)(120x100)/(280x200)
B)(120x200)/(100x280)
C)(120x280)/(100x200)
D)(120/220)/(280/480)
E)(120/400)/(100/300)

Question 75

A study compared drug A versus standard therapy in preventing recurrent pulmonary embolism (PE).  The absolute risk reduction for drug A versus standard therapy was 4%.  The incidence of recurrent PE in the standard therapy group was 6%.  There were 24 patients who developed recurrent PE in the drug A group.  How many total subjects were there in the drug A group?

A)600
B)900
C)1200
D)1500
E)1800
F)2100

Question 76

An epidemiological study is initiated to assess the impact of type II diabetes mellitus in a large population with little migration.  Disease incidence and prevalence are monitored and recorded as the number of cases per 1,000 individuals over a 30-year period. Which of the following is the most likely explanation for the change in disease prevalence seen in the graph?

A)Decreased hospitalization rate
B)High mortality in diabetics
C)Improved quality of care
D)Increased accuracy of diagnostic testing
E)Increased exposure to risk factors
F)Increased number of new diabetes cases
G)Selective survival bias

Question 77

A 65-year-old man comes to the office because his family is concerned about his constant cough after smoking.  The patient asks about the risk of developing chronic obstructive pulmonary disease (COPD) in adult smokers.  A recent cohort study reported that compared to heavy smokers, the relative risk (RR) of COPD for nonsmokers is 0.10 and for moderate smokers is 0.40.  The patient is a moderate smoker.  Based on the study, which of the following is the RR of COPD for moderate smokers compared to nonsmokers?

A)0)10
B)0)25
C)0)40
D)2)5
E)4
F)10

Question 78

A 73-year-old man comes to the office for follow-up.  He was diagnosed with chronic lymphocytic leukemia (CLL) 3 years ago when routine laboratory testing revealed a markedly elevated leukocyte count.  He feels well.  On examination, he has stable lymphadenopathy.  He has been reading about management options should his CLL progress and inquires about an experimental drug that selectively binds malignant lymphocytes.  The drug has been shown to significantly prolong survival in patients with stage 3 and 4 CLL, without curing the malignancy.  If this new drug were widely used, what changes would be expected in the number of incident and prevalent cases of CLL?

A)The number of incident cases will decrease, the number of prevalent cases will decrease
B)The number of incident cases will increase, the number of prevalent cases will not change
C)The number of incident cases will decrease, the number of prevalent cases will increase
D)The number of incident cases will not change, the number of prevalent cases will increase
E)The number of incident cases will not change, the number of prevalent cases will not change

Question 79

A new study is conducted to investigate the efficacy of intravenous immunoglobulin versus analgesics on pain alleviation in patients with idiopathic small fiber neuropathy.  A total of 100 eligible patients who fulfilled the inclusion/exclusion criteria are assigned to one of two groups based on random selection by a computer.  The method of assigning patients to treatment groups in this study is most likely to produce which of the following?

A)One group in which participants are blinded to the intervention they receive and another in which participants are not
B)One group in which researchers but not participants are aware of the intervention received and another in which participants but not researchers are aware of the intervention received
C)Two groups of participants that will only be analyzed based on their initial treatment allocation
D)Two groups that have equal numbers of participants
E)Two groups in which participants are similar in underlying characteristics

Question 80

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?

A)25%
B)50%
C)70%
D)80%
E)90%