40 Epidemiology Questions And Answers

QUESTION 1 1. In 2013, the number of new cases of influenza was 250 in Somerville and 1,075 in Boston. Which city had a higher cumulative incidence of influenza in 2013?

a. Somerville

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b. Boston

c. Can’t be determined based on the information given

 

QUESTION 2 1. In January, 2001 forty heterosexual hemophiliac patients (all males) were asked to participate in a 3 year prospective study . The men were to undergo an interview, physical examination, and blood testing for HIV status every 6 months for 3 years. Among the 40 subjects there were 30 who were seronegative and healthy for the entire duration of the study, and all of these were followed for the entire 3 years. During the initial screening, 2 of the men were found to already be HIV+, although none of them had clinical signs of AIDS. The table below describes the 10 subjects who either tested HIV positive, or became lost to follow-up, or already were HIV positive at the start of the study. Legend: HIV+ = found to be HIV+ at the very beginning of the interval observation period ? = lost to follow-up ************* Follow-up ********************** Subject # 1 2 3 4 5 6 7 8 9 10 Initial Screening HIV+ HIV+ Jan. 2001 ——— ——— ——— ——— ——— ——— ——— ——— ——— ——— June 2001 ——— ——— ——— ? ——— ——— HIV+– ——— ——— ——— Jan. 2002 ——— ——— HIV+– ——— ——— ——— ——— ——— ——— June 2002 ——— ——— ——— ? ——— ——— ——— ——— ——— Jan. 2003 ——— ——— ——— ——— ——— ——— ——— ——— June 2003 HIV+– ? ——— ? ——— ? ——— ? What was the cumulative incidence of seropositivity (HIV+) during the 3 year study? a. 5/40 b. 3/10 c. 5/35 d. 3/38

 

QUESTION 3 1. What is the main limitation of a case series?

a. It is difficult to find an adequate exposure group.

b. There is no explicit comparison group.

c. It measures effects at the population, not the individual, level.

d. It is difficult to obtain approval to conduct these studies.

 

QUESTION 4 1. Which of the following is an example of incidence rate? the number of newly diagnosed breast cancer cases diagnosed during 200 person-years of follow-up the number of men who were found to have high blood pressure at their yearly physical exam the percentage of infants born with spina bifida (a type of birth defect) among 1,000 liveborn infants

 

QUESTION 5 1. A cohort study of coffee drinking and anxiety was conducted at a university campus. There were a total of 30,000 freshmen who participated. 10,000 were coffee drinkers and 20,000 were not. Of the coffee drinkers, 500 developed anxiety during the 4 year follow-up period. Of the non-coffee drinkers, 200 developed anxiety during the same time period. Assume that no one in the population died or was lost during the follow-up period. Which of the following is the correct interpretation of the population risk difference calculated from this study?

a. Coffee drinkers are “x” times as likely to develop anxiety as compared to non-coffee drinkers.

b. The excess risk of anxiety among the coffee drinkers is “x”

c. The excess risk of anxiety among the entire freshmen population is “x”

d. None of the above

 

QUESTION 6 1. Which measure of disease frequency best describes the following: the number of healthy, at risk women in the Black Women’s Health Study who develop hypertension during 121,600 person-years of follow-up.

a. Prevalence

b. Cumulative incidence

c. Incidence rate

d. None of the above

 

QUESTION 7 1. Which of the following is an example of a “fixed” population?

a. The patient population of Boston Medical Center

b. Spring 2012 graduates of BUSPH

c. The residents of the City of Cambridge

d. The student body of BUSPH

 

QUESTION 9 1. What can randomization do that no other method to control confounding can do?

a. It can control for known confounders

b. It can assure there is no bias in the study results

c. It can automatically assess effect modification

d. It can prevent self-selection of subjects into the groups being compared

 

 

QUESTION 10 1. In January, 2001 forty heterosexual hemophiliac patients (all males) were asked to participate in a 3 year prospective study . The men were to undergo an interview, physical examination, and blood testing for HIV status every 6 months for 3 years. Among the 40 subjects there were 30 who were seronegative and healthy for the entire duration of the study, and all of these were followed for the entire 3 years. During the initial screening, 2 of the men were found to already be HIV+, although none of them had clinical signs of AIDS. The table below describes the 10 subjects who either tested HIV positive, or became lost to follow-up, or already were HIV positive at the start of the study. Legend: HIV+ = found to be HIV+ at the very beginning of the interval observation period ? = lost to follow-up Subject # Initial Screening 1 2 3 4 5 6 7 8 9 HIV+ 10 HIV+ ************* Follow-up ********************** Jan. 2001 ——— ——— ——— ——— ——— ——— ——— ——— ——— ——— June 2001 ——— ——— ——— ? ——— ——— HIV+– ——— ——— ——— Jan. 2002 ——— ——— HIV+– ——— ——— ——— ——— ——— ——— June 2002 ——— ——— ——— ? ——— ——— ——— ——— ——— Jan. 2003 ——— ——— ——— ——— ——— ——— ——— ——— June 2003 HIV+– ? ——— ? ——— ? ——— ? From the information above, what was the prevalence of seropositivity

a. 4/40

b. 5/10

c. 4/39

d. 2/40

 

QUESTION 11 (HIV+) in Jan. 2002?\ 1. Three principles guide research that involves human participants. These are:

a) Respect for persons, beneficence, and justice

b) Confidentiality, compensation, and avoiding harm

c) Equitable access to benefits of research, moral rightness in action or attitude, minimizing risk

 

QUESTION 12 1. If an exposure has no association with an outcome, then the odds ratio will be 1. true or false

 

QUESTION 13 1. In January, 2001 forty heterosexual hemophiliac patients (all males) were asked to participate in a 3 year prospective study . The men were to undergo an interview, physical examination, and blood testing for HIV status every 6 months for 3 years. Among the 40 subjects there were 30 who were seronegative and healthy for the entire duration of the study, and all of these were followed for the entire 3 years. During the initial screening, 2 of the men were found to already be HIV+, although none of them had clinical signs of AIDS. The table below describes the 10 subjects who either tested HIV positive, or became lost to follow-up, or already were HIV positive at the start of the study. Legend: HIV+ = found to be HIV+ at the very beginning of the interval observation period ? = lost to follow-up Subject # Initial Screening 1 2 3 4 5 6 7 8 9 HIV+ 10 HIV+ ************* Follow-up ********************** Jan. 2001 ——— ——— ——— ——— ——— ——— ——— ——— ——— ——— June 2001 ——— ——— ——— ? ——— ——— HIV+– ——— ——— ——— Jan. 2002 ——— ——— HIV+– ——— ——— ——— ——— ——— ——— June 2002 ——— ——— ——— ? ——— ——— ——— ——— ——— Jan. 2003 ——— ——— ——— ——— ——— ——— ——— ——— June 2003 HIV+– ? ——— ? ——— ? ——— ? What were the total person-months at risk during the study?

a. 162

b. 1,242

c. 1,080

d. It is not possible to calculate total person-months with the information given.

 

QUESTION 14 1. Which measure of disease frequency best describes the following: the percentage of nursing home residents who have bed sores on July 1, 2012.

a. Prevalence

b. Cumulative incidence

c. Incidence rate

d. None of the above

 

QUESTION 15 1. Suppose that your company has just developed a new screening test for a disease and you are in charge of testing its validity and feasibility. You decide to evaluate the test on 1000 individuals and compare the results of the new test to the gold standard. You know the prevalence of disease in your population is 30%. The screening test gave a positive result for 292 individuals. 285 of these individuals actually had the disease on the basis of the gold standard determination. Calculate the specificity of the new screening test:

a. 95%

b. 97.6%

c. 93.7%

d. 99%

 

 

QUESTION 16 1. Differential misclassification can bias study results in which direction?

a. Towards the null

b. Away from the null

c. Either towards or away from the null

 

QUESTION 17 1. A study was conducted on the relationship between folic acid supplementation during pregnancy and the risk of having a child with a neural tube defect. The risk ratio comparing supplemented versus non-supplemented women was 0.33. This means that women who take folic acid were 67% less likely to have a child with a neural tube defect. true or false

 

QUESTION 18 1. The ideal comparison group in a cohort study…

a. Is as similar as possible to the exposed group with respect to other factors that could influence the development of disease.

b. Would, if possible, consist of exactly the same individuals in the exposed group had they not been exposed.

c. Both of the above

d. Neither of the above

 

QUESTION 19 1. What would happen to the predictive value positive if a screening test were administered in a population with a disease prevalence of 1% instead of 30%? (Assume that the sensitivity and specificity of the test remain the same.)

a. The predictive value positive would remain the same.

b. The predictive value positive would increase.

c. The predictive value positive would decrease.

d. It is impossible to tell from the information given.

 

QUESTION 20 1. A case-control study was conducted to evaluate the relationship between aspirin use and the risk of colon cancer. 2,000 cases and 2,000 controls were enrolled in the study. 1,800 of the cases reported using aspirin in the past while 1,200 of the controls reported using aspirin in the past. What measure of association should be calculated to determine the strength of the relationship between aspirin and colon cancer?

a. Rate ratio

b. Risk ratio

c. Odds ratio

d. Attributable risk

 

QUESTION 21 1. Suppose that we undertake a cohort study to examine the association of high salt intake and hypertension. Our study population consists of male and female Hispanics and Caucasians. No matching or restriction is performed. Let’s assume that the following facts are true: Men consume more salt than women. Irrespective of their salt consumption, men have a greater risk of developing hypertension than women. Smokers consume the same amount of salt as non- smokers. Smoking is an independent risk factor for hypertension. Hispanics consume more salt than Caucasians. Irrespective of their salt consumption , Hispanics have the same risk of hypertension as Caucasians. Based on the above information, which of the following are likely confounders in this study?

a. Gender

b. Smoking

c. Race/ethnicity

d. All of the above

 

QUESTION 23 1. A cohort study of coffee drinking and anxiety was conducted at a university campus. There were a total of 30,000 freshmen who participated. 10,000 were coffee drinkers and 20,000 were not. Of the coffee drinkers, 500 developed anxiety during the 4 year follow-up period. Of the non-coffee drinkers, 200 developed anxiety during the same time period. Assume that no one in the population died or was lost during the follow-up period. Calculate the risk ratio (a.k.a. relative risk) using the given data. The numeric value of the risk ratio is…

a. 1.0

b. 0.2

c. 5.0

d. None of the above

 

QUESTION 24 1. A cohort study of coffee drinking and anxiety was conducted at a university campus. There were a total of 30,000 freshmen who participated. 10,000 were coffee drinkers and 20,000 were not. Of the coffee drinkers, 500 developed anxiety during the 4 year follow-up period. Of the non-coffee drinkers, 200 developed anxiety during the same time period. Assume that no one in the population died or was lost during the follow-up period. Calculate the population risk difference using the given data. The numeric value of the population risk difference is…

a. 1.3 (per 100)

b. 2.7 (per 100)

c. 3.3 (per 100)

d. None of the above

 

QUESTION 25 1. What type of observational study design is best suited to study a disease that has a long latent and induction period? (CHOOSE ALL THAT APPLY)

a. Case-control study

b. Retrospective cohort study

c. Cross-sectional study

d. Prospective cohort study

 

QUESTION 26 1. A population of 1,000 healthy, at risk people is monitored for one year starting on January 1st and the development of chicken pox cases is noted. No one has chicken pox at the start of the investigation. Twenty people develop chicken pox on June 30th and forty people develop chicken pox on September 30th. Twenty-four people were lost to follow-up on March 31st and twenty-four people were lost to follow-up on November 30th. None of those lost to follow-up had developed chicken pox prior to becoming lost. Assume that you can get chicken pox only once. What is the incidence rate of chicken pox in this population during the one-year period from January 1st through December 31st?

a. 60/1,000 person-years

b. 60/892 person-years

c. 60/992 person-years

d. 60/960 person-years

 

QUESTION 27 1. A cohort study of coffee drinking and anxiety was conducted at a university campus. There were a total of 30,000 freshmen who participated. 10,000 were coffee drinkers and 20,000 were not. Of the coffee drinkers, 500 developed anxiety during the 4 year follow-up period. Of the non-coffee drinkers, 200 developed anxiety during the same time period. Assume that no one in the population died or was lost during the follow-up period. What was the cumulative incidence of anxiety among coffee drinkers?

a. 2.0 % over a four year period.

b. 5.0 % over a four year period.

c. 1.0 % over a four year period.

d. None of the above

 

QUESTION 28 1. A population of 1,000 healthy, at risk people is monitored for one year starting on January 1st and the development of cases of chicken pox is noted. No one has chicken pox at the start of the investigation. Twenty people develop chicken pox on June 30th and forty people develop chicken pox on September 30th. Twenty-four people were lost to follow-up on March 31st and twenty-four people were lost to follow-up on November 30th. None of those lost to follow-up had developed chicken pox prior to becoming lost. Assume that you can get chicken pox only once. What is the cumulative incidence of chicken pox in this population during the one-year period from January 1st through December 31st?

a. 20/1,000

b. 40/1,000

c. 60/1,000

d. 60/108

 

QUESTION 29 1. A cohort study of coffee drinking and anxiety was conducted at a university campus. There were a total of 30,000 freshmen who participated. 10,000 were coffee drinkers and 20,000 were not. Of the coffee drinkers, 500 developed anxiety during the 4 year follow-up period. Of the non-coffee drinkers, 200 developed anxiety during the same time period. Assume that no one in the population died or was lost during the follow-up period. Which of the following is the correct interpretation of a risk ratio calculated from this study?

a. Coffee drinkers are “x” times as likely to develop anxiety as compared to non-coffee drinkers.

b. The excess risk of anxiety among coffee drinkers is “x” as compared to non-coffee drinkers.

c. The excess risk of anxiety among the entire freshmen population is “x”

d. None of the above

 

QUESTION 30 1. Which of the following methods can be used to minimize recall bias in a case-control study? (CHOOSE ALL THAT APPLY)

a. blind subjects to the study hypothesis

b. blind interviewers to the study hypothesis

c. avoid open-ended interview questions

d. use a control group comprised of diseased individuals

 

QUESTION 31 1. In an experimental study design, when the study participants do not know if they are in the treatment or comparison group but the investigators do, this is called a:

a. Double-blinded study

b. Single-blinded study

c. Equipoise study

d. Intent-to-treat study

 

QUESTION 32 1. Suppose that your company has just developed a new screening test for a disease and you are in charge of testing its validity and feasibility. You decide to evaluate the test on 1000 individuals and compare the results of the new test to the gold standard. You know the prevalence of disease in your population is 30%. The screening test gave a positive result for 292 individuals. 285 of these individuals actually had the disease on the basis of the gold standard determination. Calculate the predictive value of a positive test:

a. 93.7%

b. 97.6%

c. 99%

d. 95%

 

QUESTION 33 1. Suppose that your company has just developed a new screening test for a disease and you are in charge of testing its validity and feasibility. You decide to evaluate the test on 1000 individuals and compare the results of the new test to the gold standard. You know the prevalence of disease in your population is 30%. The screening test gave a positive result for 292 individuals. 285 of these individuals actually had the disease on the basis of the gold standard determination. Calculate the sensitivity of the new screening test:

a. 97.6%

b. 95%

c. 99%

d. 93.7%

 

QUESTION 34 1. Which type of measure of disease frequency best describes the following: the percentage of healthy, at-risk children in a daycare who develop impetigo (a skin disease) during March 2012.

a. Prevalence

b. Incidence rate

c. Cumulative incidence

d. None of the above

 

QUESTION 36 1. Consider the situation in a cohort study where the crude risk ratio is 2.5. The data are then divided into two groups. In the first group the group-specific risk ratio is 1.0, and the second group’s risk ratio is 4.0. Which of the following is present?

a. Positive confounding

b. Negative confounding

c. No effect modification or confounding

d. Effect modification, confounding irrelevant

 

QUESTION 37 1. Investigators began a study in 1995 to evaluate the association between infertility treatment and ovarian cancer occurrence among 3,000 Rhode Island women treated for infertility between 1984 and 1994. Cancer incidence was determined by matching the women to information in the Rhode Island Cancer Registry. The cancer rates in this sample were compared with cancer rates among the population of Rhode Island women. What kind of cohort study is this?

a. Retrospective

b. Prospective

c. Ambidirectional

 

QUESTION 38 1. Consider the situation in a case-control study where the crude odds ratio is 4.6. The data are then divided into two groups. In the first group the group-specific odds ratio is 1.0, and the second group’s odds ratio is 3.0. Which of the following is present?

a. Positive confounding

b. Negative confounding

c. Positive confounding and effect modification

d. Negative confounding and effect modification

 

QUESTION 39 1. A cohort study of coffee drinking and anxiety was conducted at a university campus. There were a total of 30,000 freshmen who participated. 10,000 were coffee drinkers and 20,000 were not. Of the coffee drinkers, 500 developed anxiety during the 4 year follow-up period. Of the non-coffee drinkers, 200 developed anxiety during the same time period. Assume that no one in the population died or was lost during the follow-up period. Calculate the risk difference using the given data. The numeric value of the risk difference is…

a. 6.0 %

b. 4.0 %

c. 5.0 %

d. None of the above

 

QUESTION 40 1. Suppose that you began a one-year study of tuberculosis (TB) on January 1st, 2013. You enrolled 500 residents in your study and checked on their TB status on a monthly basis. At the start of your study on January 1st, you screened all 500 residents. 30 residents already had existing cases of TB on January 1st. On February 1st, 5 residents developed TB. On April 1st, 5 more residents developed TB. On July 1st, 10 of the residents who had existing TB on January 1st died from their disease. The study ended on December 31, 2010. Assume that once a person gets TB, they have it for the duration of the study, and assume that all remaining residents stayed healthy and were not lost to follow-up. What was the case-fatality rate among residents with TB over the course of the year?

a. 0%

b. 25%

c. 50%

d. 100%

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