MCQ Quiz: Case-Control Studies & Self-Controlled Designs

Understanding different pharmacoepidemiologic study designs is a critical skill for the modern pharmacist. As outlined in the Patient Care and Pharmacoepidemiology and Drug Safety courses, the ability to critically appraise literature, including case-control and self-controlled studies, is essential for making evidence-based decisions to achieve positive patient outcomes. This quiz will test your knowledge of these important observational study designs, focusing on their structure, measures of association, biases, and the unique advantages of self-controlled methods, all key transcending concepts in your curriculum.

1. What is the fundamental design of a case-control study?

• A. A study that follows a group of exposed and unexposed individuals forward in time to see who develops a disease.
• B. A study that starts with individuals who have a disease (“cases”) and a comparable group without the disease (“controls”) and looks back retrospectively to compare past exposures.
• C. A study that randomly assigns individuals to an intervention or a placebo.
• D. A study that analyzes population-level data at a single point in time.

Answer: B. A study that starts with individuals who have a disease (“cases”) and a comparable group without the disease (“controls”) and looks back retrospectively to compare past exposures.

2. Case-control studies are particularly efficient and well-suited for studying which type of diseases?

• A. Diseases with a very high incidence.
• B. Diseases that take a short time to develop.
• C. Very common diseases.
• D. Diseases that are rare.

Answer: D. Diseases that are rare.

3. What is the primary measure of association calculated in a case-control study?

• A. Relative Risk (RR)
• B. Attributable Risk (AR)
• C. Odds Ratio (OR)
• D. Incidence Rate

Answer: C. Odds Ratio (OR)

4. In a self-controlled design, such as a self-controlled case series (SCCS), who serves as the control?

• A. A matched group of unexposed individuals from the same hospital.
• B. The cases themselves, during periods when they are not exposed (control periods).
• C. A randomly selected group from the general population.
• D. The cases’ siblings or other family members.

Answer: B. The cases themselves, during periods when they are not exposed (control periods).

5. A major advantage of a self-controlled design is that it automatically controls for:

• A. Time-varying confounders like age.
• B. Time-invariant confounders that are constant within an individual (e.g., genetics, socioeconomic status).
• C. All forms of bias.
• D. The placebo effect.

Answer: B. Time-invariant confounders that are constant within an individual (e.g., genetics, socioeconomic status).

6. Recall bias is a major concern in case-control studies. It occurs when:

• A. The investigator is aware of the patient’s disease status and asks questions differently.
• B. Cases (who have the disease) remember their past exposures differently than controls (who do not).
• C. The control group is not representative of the population that produced the cases.
• D. A third variable is associated with both the exposure and the outcome.

Answer: B. Cases (who have the disease) remember their past exposures differently than controls (who do not).

7. In a case-control study examining the link between an antidepressant and birth defects, the Odds Ratio is calculated to be 3.0. How is this interpreted?

• A. The risk of birth defects is three times higher in antidepressant users.
• B. The odds of having been exposed to the antidepressant were three times higher among cases (infants with birth defects) compared to controls.
• C. The antidepressant causes birth defects.
• D. The risk of birth defects is 3%.

Answer: B. The odds of having been exposed to the antidepressant were three times higher among cases (infants with birth defects) compared to controls.

8. Why can’t a case-control study directly calculate the incidence or relative risk of a disease?

• A. Because the study is always prospective.
• B. Because the study starts with diseased and non-diseased individuals, so the proportion of diseased individuals is fixed by the researcher, not the true population rate.
• C. Because the odds ratio is always equal to the relative risk.
• D. Because these studies are not subject to bias.

Answer: B. Because the study starts with diseased and non-diseased individuals, so the proportion of diseased individuals is fixed by the researcher, not the true population rate.

9. Self-controlled designs are most appropriate for studying the association between:

• A. A chronic exposure and a chronic disease.
• B. A transient, acute exposure and an acute event.
• C. A constant exposure (like genetics) and an outcome.
• D. A rare exposure and a common outcome.

Answer: B. A transient, acute exposure and an acute event.

10. The selection of an appropriate control group is the most critical and difficult part of designing a case-control study. The ideal control group should:

• A. Come from a population that is entirely different from the cases.
• B. Have a much higher prevalence of the exposure than the cases.
• C. Represent the baseline exposure distribution in the population from which the cases arose.
• D. Be composed entirely of hospital patients, regardless of the source of cases.

Answer: C. Represent the baseline exposure distribution in the population from which the cases arose.

11. An Odds Ratio of 1.0 implies that the exposure:

• A. Is a strong risk factor for the disease.
• B. Is protective against the disease.
• C. Is not associated with the odds of having the disease.
• D. Could not be measured.

Answer: C. Is not associated with the odds of having the disease.

12. A key difference between a case-control study and a retrospective cohort study is:

• A. Case-control studies are experimental, while cohort studies are observational.
• B. Case-control studies start by identifying subjects based on their outcome (disease) status, while cohort studies start by identifying subjects based on their exposure status.
• C. Case-control studies are always larger than cohort studies.
• D. Case-control studies can calculate relative risk, while cohort studies cannot.

Answer: B. Case-control studies start by identifying subjects based on their outcome (disease) status, while cohort studies start by identifying subjects based on their exposure status.

13. Which of the following is a significant strength of a case-control study design?

• A. It is immune to recall bias.
• B. It is good for studying multiple outcomes from a single exposure.
• C. It is relatively quick to conduct and less expensive than a cohort study.
• D. It provides definitive proof of causation.

Answer: C. It is relatively quick to conduct and less expensive than a cohort study.

14. A “transcending concept” in the Patient Care curriculum is the evaluation of different study designs to inform clinical practice. Appraising a case-control study requires careful assessment of potential:

• A. Randomization methods.
• B. Blinding procedures.
• C. Selection bias and recall bias.
• D. Non-inferiority margins.

Answer: C. Selection bias and recall bias.

15. In a self-controlled case series studying the risk of seizures after a vaccine, the “risk period” would be:

• A. The time period immediately before vaccination.
• B. The entire lifetime of the participant.
• C. A defined time window immediately following vaccination (e.g., days 1-14).
• D. The time period several years after vaccination.

Answer: C. A defined time window immediately following vaccination (e.g., days 1-14).

16. An Odds Ratio of 0.5 suggests that the exposure:

• A. Doubles the odds of the disease.
• B. Has no association with the disease.
• C. Is associated with a 50% reduction in the odds of the disease (i.e., it is protective).
• D. Is a very strong risk factor for the disease.

Answer: C. Is associated with a 50% reduction in the odds of the disease (i.e., it is protective).

17. What is the primary directionality of inquiry in a case-control study?

• A. Forward, from exposure to outcome.
• B. Backward, from outcome to exposure.
• C. It has no directionality.
• D. It is both forward and backward simultaneously.

Answer: B. Backward, from outcome to exposure.

18. A major limitation of the case-control design is that it:

• A. Cannot be used for rare diseases.
• B. Can be very expensive and time-consuming.
• C. Is generally considered to provide weaker evidence than a well-designed cohort study.
• D. Is immune to confounding.

Answer: C. Is generally considered to provide weaker evidence than a well-designed cohort study.

19. How does a self-controlled design minimize confounding by indication?

• A. By randomly assigning patients to the exposure.
• B. By blinding the investigator to the patient’s exposure status.
• C. By comparing risk within the same person, the underlying reasons for needing the exposure (the indication) are likely constant across risk and control periods.
• D. By only including healthy patients in the study.

Answer: C. By comparing risk within the same person, the underlying reasons for needing the exposure (the indication) are likely constant across risk and control periods.

20. In a case-control study, if the controls are not properly selected and have a much lower prevalence of the exposure than the source population, what type of bias might occur?

• A. Recall bias
• B. Selection bias
• C. Observer bias
• D. Confounding

Answer: B. Selection bias

21. When can the Odds Ratio from a case-control study provide a good approximation of the Relative Risk?

• A. When the disease is very common.
• B. When the exposure is very common.
• C. When the disease being studied is rare in the population.
• D. The OR never approximates the RR.

Answer: C. When the disease being studied is rare in the population.

22. A key assumption of the self-controlled case series (SCCS) design is that:

• A. The occurrence of the event (e.g., a seizure) does not influence subsequent exposure (e.g., getting another vaccine).
• B. All participants must have the same genetics.
• C. The exposure must be chronic and lifelong.
• D. The risk period must last for several years.

Answer: A. The occurrence of the event (e.g., a seizure) does not influence subsequent exposure (e.g., getting another vaccine).

23. A case-crossover study is a type of case-control design where:

• A. Cases are matched with controls from a different country.
• B. The exposure status of cases is compared across different time periods.
• C. Cases serve as their own controls, comparing exposure status in a time window just before the event to a control time window earlier.
• D. The study is prospective.

Answer: C. Cases serve as their own controls, comparing exposure status in a time window just before the event to a control time window earlier.

24. Which of the following is a disadvantage of a case-control study?

• A. It requires a very large number of subjects.
• B. It is not suitable for studying exposures with long latency periods.
• C. It can be difficult to establish a clear temporal relationship between the exposure and the outcome.
• D. It can study many different diseases at once.

Answer: C. It can be difficult to establish a clear temporal relationship between the exposure and the outcome.

25. A case-control study is classified as what type of study design?

• A. Experimental
• B. Observational
• C. Quasi-experimental
• D. A meta-analysis

Answer: B. Observational

26. The “ORs vs RRs” distinction is listed as a topic in

PHA5789C Unit 5.7. A Relative Risk (RR) is calculated in which type of study?

• A. Case report
• B. Case-control study
• C. Cohort study
• D. Cross-sectional study

Answer: C. Cohort study

27. To reduce recall bias in a case-control study, a researcher might:

• A. Use pre-existing records (e.g., pharmacy dispensing data) to ascertain exposure instead of relying on patient memory.
• B. Only include cases in the study.
• C. Ask cases more detailed questions than controls.
• D. Use a placebo.

Answer: A. Use pre-existing records (e.g., pharmacy dispensing data) to ascertain exposure instead of relying on patient memory.

28. What is the main research question a case-control study aims to answer?

• A. “What is the incidence of the disease in the exposed group?”
• B. “Are the odds of past exposure different between those who have the disease and those who do not?”
• C. “What is the effect of the intervention on the outcome?”
• D. “What is the prevalence of the disease at this point in time?”

Answer: B. “Are the odds of past exposure different between those who have the disease and those who do not?”

29. The concept of “confounding” is a central challenge in observational studies. It is described in the

PHA5244 curriculum. A variable is a confounder if it is associated with both the exposure and the:

• A. Investigator.
• B. Control group only.
• C. Outcome, and is not on the causal pathway.
• D. Study funding source.

Answer: C. Outcome, and is not on the causal pathway.

30. Self-controlled designs are part of the broader category of pharmacoepidemiology studies that evaluate:

• A. Only the intended benefits of drugs.
• B. The use and effects of drugs in large numbers of people.
• C. The chemical structure of new drugs.
• D. The cost-effectiveness of medications.

Answer: B. The use and effects of drugs in large numbers of people.

31. In a case-control study, “matching” is a technique sometimes used during subject selection to:

• A. Introduce bias into the study.
• B. Control for the effects of specific confounding variables (e.g., age, sex).
• C. Ensure that cases and controls have different exposures.
• D. Make the study more expensive.

Answer: B. Control for the effects of specific confounding variables (e.g., age, sex).

32. The “cases” in a case-control study are selected based on:

• A. Their exposure history.
• B. The presence of the disease or outcome of interest.
• C. Their willingness to participate.
• D. A random number generator.

Answer: B. The presence of the disease or outcome of interest.

33. Which of the following questions is best answered with a case-control study?

• A. What is the overall incidence of lung cancer in the U.S.?
• B. Does a new drug lower blood pressure better than a placebo?
• C. Is a history of exposure to a rare chemical associated with the development of a specific rare cancer?
• D. How many people in this room have brown hair?

Answer: C. Is a history of exposure to a rare chemical associated with the development of a specific rare cancer?

34. A major benefit of self-controlled designs is the elimination of between-person confounding. This is because:

• A. They use very large sample sizes.
• B. They only study healthy people.
• C. Comparisons are made within each person, so stable characteristics like genetics are inherently controlled for.
• D. They are a type of randomized controlled trial.

Answer: C. Comparisons are made within each person, so stable characteristics like genetics are inherently controlled for.

35. A “nested” case-control study is one where:

• A. The cases and controls are selected from within a previously defined cohort study.
• B. The study is conducted entirely online.
• C. The investigators and participants are both blinded.
• D. The outcome of interest is very common.

Answer: A. The cases and controls are selected from within a previously defined cohort study.

36. A pharmacist critically appraising a case-control study should pay close attention to the methods section to understand:

• A. How the drug was manufactured.
• B. The statistical power calculation.
• C. The definition of cases and the source and selection criteria for controls.
• D. The informed consent process.

Answer: C. The definition of cases and the source and selection criteria for controls.

37. An Odds Ratio of 2.5 has a 95% Confidence Interval of (1.5 – 4.1). What can be concluded?

• A. The result is not statistically significant.
• B. The exposure is protective.
• C. The result is statistically significant because the interval does not include 1.0.
• D. The study was biased.

Answer: C. The result is statistically significant because the interval does not include 1.0.

38. Self-controlled designs cannot be used to study:

• A. The acute effects of vaccines.
• B. The effects of exposures that are constant or do not change over time (e.g., genetics).
• C. The side effects of intermittent medications.
• D. The risk of heart attack after starting a new drug.

Answer: B. The effects of exposures that are constant or do not change over time (e.g., genetics).

39. In pharmacoepidemiology, a case-control study would be a good design to investigate:

• A. The overall effectiveness of a new cholesterol medication.
• B. A potential link between a widely used drug and a very rare adverse event.
• C. The incidence of the common cold in a population.
• D. The prevalence of hypertension in a community.

Answer: B. A potential link between a widely used drug and a very rare adverse event.

40. A key weakness of the case-control design is the difficulty in assembling a control group that is free from:

• A. Any prior medical history.
• B. Selection bias.
• C. Exposure to the drug of interest.
• D. The ability to recall past events.

Answer: B. Selection bias.

41. The first step in conducting a case-control study is always to:

• A. Identify the exposure of interest.
• B. Define and identify the cases.
• C. Select the control group.
• D. Perform the statistical analysis.

Answer: B. Define and identify the cases.

42. Which design inherently ensures that cases and controls have the same fixed characteristics like sex and ethnicity?

• A. A traditional case-control study.
• B. A randomized controlled trial.
• C. A self-controlled design.
• D. A cross-sectional study.

Answer: C. A self-controlled design.

43. A case-control study is often described as being “retrospective” because it:

• A. Looks forward in time.
• B. Involves random assignment.
• C. Looks backward in time from outcome to exposure.
• D. Is conducted in a laboratory.

Answer: C. Looks backward in time from outcome to exposure.

44. A patient with a disease may be more likely to remember using a certain medication than a healthy person. This is the classic definition of:

• A. Selection bias.
• B. Confounding.
• C. Recall bias.
• D. Observer bias.

Answer: C. Recall bias.

45. If a case-control study finds an association, it is important for the pharmacist to remember that:

• A. It proves causation definitively.
• B. It suggests an association that may need to be confirmed by stronger study designs, like a cohort study.
• C. The study is flawed and should be ignored.
• D. The drug should be immediately removed from the market.

Answer: B. It suggests an association that may need to be confirmed by stronger study designs, like a cohort study.

46. A primary limitation of a self-controlled design is that it is not suitable for outcomes that:

• A. Are very rare.
• B. Are acute and occur shortly after exposure.
• C. Alter the probability of future exposure.
• D. Are easily measured in health records.

Answer: C. Alter the probability of future exposure.

47. When reading a case-control study, the “Methods” section should be scrutinized to understand how:

• A. The results were marketed to the public.
• B. The cases and controls were selected and how exposure was ascertained.
• C. The authors decided on the topic.
• D. The journal was chosen for publication.

Answer: B. The cases and controls were selected and how exposure was ascertained.

48. A case-control study is a powerful tool in drug safety to:

• A. Determine the incidence of an adverse event.
• B. Generate hypotheses about potential rare adverse drug reactions.
• C. Prove that a drug is 100% safe.
• D. Establish the cost-effectiveness of a medication.

Answer: B. Generate hypotheses about potential rare adverse drug reactions.

49. An odds ratio is a ratio of two odds. In a case-control study, it is the odds of _________ among cases divided by the odds of _________ among controls.

• A. Disease; disease
• B. Exposure; exposure
• C. Disease; exposure
• D. Exposure; disease

Answer: B. Exposure; exposure

50. The ability to critically evaluate different study designs, including case-control studies, is a foundational skill for which pharmacy practice concept?

• A. Sterile compounding
• B. Evidence-Based Practice
• C. Pharmacy Law
• D. Inventory Management

Answer: B. Evidence-Based Practice