Prospective vs retrospective study designs MCQs With Answer

Introduction

This quiz collection on Prospective vs Retrospective Study Designs is tailored for M.Pharm students studying Clinical Research (MPP 104T). It explains core concepts, strengths and limitations, typical biases, appropriate outcome and exposure measures, and analytical choices when comparing prospective and retrospective approaches. Questions target practical decision-making — when to choose a design, how to handle temporality, which measures (relative risk, odds ratio, hazard ratio) are appropriate, and how to reduce bias using data sources or nested designs. These MCQs emphasize deeper understanding needed for planning pharmacoepidemiology and clinical observational studies, helping students apply methodological principles to real research scenarios.

Q1. What best describes a prospective study design?

• Data on exposures and outcomes are collected at a single point in time
• Participants are identified after outcomes have occurred and past exposures are reconstructed
• Participants are enrolled and followed forward in time from exposure assessment to outcome occurrence
• Only cross-sectional associations without follow-up are measured

Correct Answer: Participants are enrolled and followed forward in time from exposure assessment to outcome occurrence

Q2. Which statement most accurately defines a retrospective study?

• It enrolls subjects and collects exposure data prospectively before outcomes occur
• It uses existing records or data to identify exposures and outcomes that have already occurred
• It randomizes participants to different exposures and follows them for outcome
• It measures current prevalence of disease without any temporal direction

Correct Answer: It uses existing records or data to identify exposures and outcomes that have already occurred

Q3. What is a primary advantage of prospective cohort studies over retrospective designs?

• Lower cost and shorter study duration
• Better ability to establish temporality and standardize exposure measurement before outcome occurs
• No risk of loss to follow-up
• Guaranteed absence of confounding

Correct Answer: Better ability to establish temporality and standardize exposure measurement before outcome occurs

Q4. Which is a major limitation of prospective cohort studies?

• They cannot estimate incidence or risk
• They are usually inexpensive and quick to complete
• They often require large sample sizes, long follow-up and substantial cost
• They always produce biased results due to recall error

Correct Answer: They often require large sample sizes, long follow-up and substantial cost

Q5. Which type of bias is particularly problematic in many retrospective studies relying on participant recall?

• Observer-expectancy bias
• Recall bias
• Lead-time bias
• Performance bias

Correct Answer: Recall bias

Q6. Which measure of association is most appropriate to estimate directly in a prospective cohort study?

• Odds ratio for prevalent disease
• Relative risk (risk ratio) for incident disease
• Attributable fraction in case series
• Prevalence ratio from cross-sectional data

Correct Answer: Relative risk (risk ratio) for incident disease

Q7. In a classic retrospective case-control study, which measure is used to estimate the association between exposure and outcome?

• Risk difference from cumulative incidence
• Relative risk from cohort follow-up
• Odds ratio comparing exposure odds in cases versus controls
• Hazard ratio from Cox regression

Correct Answer: Odds ratio comparing exposure odds in cases versus controls

Q8. What is a nested case-control study?

• A case-control study that recruits cases and controls from different populations
• A case-control study conducted entirely using retrospective phone interviews
• A case-control study sampled from a defined prospective cohort, using cohort baseline data for exposure assessment
• A randomized trial where cases and controls are matched by treatment

Correct Answer: A case-control study sampled from a defined prospective cohort, using cohort baseline data for exposure assessment

Q9. Which statistical model is most appropriate when analyzing time-to-event outcomes commonly collected in prospective studies?

• Linear regression predicting final outcome value
• Logistic regression for prevalent cases only
• Cox proportional hazards model for hazard ratios
• Chi-square test for independence without time dimension

Correct Answer: Cox proportional hazards model for hazard ratios

Q10. How does a retrospective cohort differ methodologically from a prospective cohort?

• Retrospective cohorts randomize exposure while prospective cohorts do not
• Retrospective cohorts identify exposure and outcome events from existing records when both have already occurred; prospective cohorts collect exposure before outcomes occur and follow forward
• Retrospective cohorts can measure incidence directly but prospective cohorts cannot
• There is no difference; they are the same design and data collection timing

Correct Answer: Retrospective cohorts identify exposure and outcome events from existing records when both have already occurred; prospective cohorts collect exposure before outcomes occur and follow forward

Q11. For studying a rare exposure (very few people exposed), which design is generally most efficient?

• Large prospective cohort specifically recruited for rare exposure
• Case series only
• Case-control design sampling many controls per case
• Cross-sectional survey of the general population

Correct Answer: Case-control design sampling many controls per case

Q12. Considering rare outcomes, which statement comparing prospective and retrospective designs is true?

• Prospective cohorts are always more efficient for rare outcomes
• Retrospective case-control studies are often more efficient and quicker for rare outcomes
• Cross-sectional studies are best for studying rare outcomes longitudinally
• Randomized trials should be used instead of observational approaches for rare outcomes

Correct Answer: Retrospective case-control studies are often more efficient and quicker for rare outcomes

Q13. Loss to follow-up in a prospective study can produce which specific bias?

• Sampling bias due to initial recruitment only
• Ascertainment bias in retrospective record review
• Attrition bias leading to differential missing outcome data
• Recall bias from participant memory errors

Correct Answer: Attrition bias leading to differential missing outcome data

Q14. Which data source is most commonly used in retrospective pharmacoepidemiologic studies?

• Prospectively collected trial biospecimens
• Real-time direct observation by study team
• Existing electronic health records, administrative claims, or disease registries
• Daily prospective patient diaries completed by participants

Correct Answer: Existing electronic health records, administrative claims, or disease registries

Q15. Which study design is required to directly calculate incidence rates and cumulative incidence?

• Cross-sectional study measuring prevalence
• Prospective cohort study tracking new events over time
• Retrospective case series without denominators
• Standard case-control study without cohort denominators

Correct Answer: Prospective cohort study tracking new events over time

Q16. One methodological advantage of conducting a nested case-control within a prospective cohort is:

• Complete elimination of confounding without adjustment
• Ability to measure exposure after the outcome has occurred
• Efficient use of stored baseline data or biospecimens while preserving temporal order
• Guaranteed representativeness of the general population

Correct Answer: Efficient use of stored baseline data or biospecimens while preserving temporal order

Q17. Regarding temporality (exposure preceding outcome), which is correct?

• Retrospective studies always prove exposure preceded outcome
• Prospective studies inherently provide stronger evidence that exposure preceded outcome
• Cross-sectional studies are ideal to determine temporality
• Temporality is irrelevant for causal inference

Correct Answer: Prospective studies inherently provide stronger evidence that exposure preceded outcome

Q18. Which study design best facilitates repeated biomarker measurements before outcome onset?

• Retrospective chart review relying on sporadic past tests
• Cross-sectional single-sample survey
• Prospective cohort with scheduled serial sampling
• Standard case-control with post-outcome sampling only

Correct Answer: Prospective cohort with scheduled serial sampling

Q19. What is an ethical advantage often associated with retrospective studies?

• They allow experimental manipulation of exposure without consent
• They always eliminate conflicts of interest
• They use existing data and typically do not expose participants to new potential harm from study interventions
• They require no data security or privacy protections

Correct Answer: They use existing data and typically do not expose participants to new potential harm from study interventions

Q20. To minimize recall bias when conducting a retrospective study based on patient histories, the best approach is:

• Rely solely on participant memory through long questionnaires
• Use objective data sources such as medical records, pharmacy dispensing data, or registries
• Exclude any participants with missing memories regardless of record availability
• Collect exposure information only after outcome confirmation via interviews

Correct Answer: Use objective data sources such as medical records, pharmacy dispensing data, or registries

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