Module Epidemiologic Study Designs Worksheet

Name: _______________________________________

Instructions: To complete the assignment, review the modules Learning Resources, read the details for each section carefully, and provide brief answers to the questions below.

Part 1: Study Designs and Measures of Association (32 pts)

Read the following research scenarios. Identify the study design and justify your choice. Then determine the appropriate measure of association related to it.

An online survey was emailed to every 10th student in a university directory. Each student was asked about their age, sex, race/ethnicity, and alcohol consumption during the preceding 7 days. Over 50% of the students completed the survey and 71% reported drinking at least once.

1. Identify the study design (2 pts)

Cross-sectional

2. Justify your choice (4 pts)

Takes data from a single point in time from a large population, looking at numerous characteristics all at once

3. Determine the appropriate measure of association (2 pts)

Prevalence ratio

Using electronic medical records at a large research hospital, 500 patients diagnosed with sepsis are matched to 500 patients who do not have sepsis based on sex, age, and reason for admission. Researchers assess length of stay in the hospital and intensive care unit (ICU) admission for possible association to sepsis.

4. Identify the study design (2 pts)

Matched-case control

5. Justify your choice (4 pts)

Allows for comparison of patients with sepsis to patients without sepsis who match on other variables; it is also retrospective in that it looks at outcomes after exposure

6. Determine the appropriate measure of association (2 pts)

Odds ratio

A random sample of men from four hospital systems were given a colonoscopy. Half of the men diagnosed with colorectal cancer were assigned to a novel drug treatment and the other half were assigned to the gold standard treatment (surgery and radiation). Both groups were followed for 5 years to monitor recurrent cancer and survival.

7. Identify the study design (2 pts)

Randomized controlled trial

8. Justify your choice (4 pts)

Participants are randomly assigned to a new intervention or to the control (standard intervention) as a way to test efficacy of new intervention compared to standard over 5 years

9. Determine the appropriate measure of association (2 pts)

Risk ratio

Data and biologic materials have been collected from 5,000 participants coming from 250 families in Jackson, Mississippi since 2000....

Annual follow-up interviews and surveillance monitor incidence of heart failure, stroke, and coronary heart disease.

10. Identify the study design (2 pts)

Prospective cohort

11. Justify your choice (4 pts)

Follows over time a single group of participants; obtains baseline data and then later at two follow-ups; has the goal of observing heart issues over a defined period of time

12. Determine the appropriate measure of association (2...

…received the vaccine and who received the placebo, which can be achieved by making sure vaccine and placebo have the same appearance at delivery

17.What ethical considerations should be taken into account for this RCT? (4 pts)

Make sure to get informed consent from participants; make sure care is available for anyone who has adverse reactions; make sure confidentiality is preserved; make sure protocols are followed to protect the validity of the study

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Part 5: Pros and Cons of Case-Control and Cohort Studies (8 pts)

Different study designs have particular advantages and disadvantages. Contrast the case-control and cohort study designs (assuming primary data collection) with respect to the following factors. Answers can be short statements.

Factor

Case-Control

Cohort

18. Cost (2 pts)

Less expensive (shorter duration, smaller sample)

More expensive (longer follow-up periods, larger samples)

19. Time required for completion of study (2 pts)

Shorter (retrospective)

Longer (prospective and needs follow-up data)

20. Design issues (recruitment and selection of participants) (2 pts)

Easier to recruit cases and controls retrospectively although there is potential risk of selection bias

Recruitment can be a challenge due to need for large sample and long-term follow-up

21. Difficulties in obtaining information (measurement and follow-up) (2 pts)

Relies on historical data, which might not be complete or might depend on recall bias

Requires consistent follow-up and data collection over a long period of time and so there is potential for loss if follow-ups fail

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