Clinical Research & Study Design Flashcards

In a crossover trial, what is the primary purpose of the washout period?

Answer: To eliminate carryover effects from the first treatment

The washout period ensures the first treatment is cleared from participants before they receive the second, preventing carryover bias.

Which study design is most appropriate for evaluating a rare adverse event that occurs in 1 in 10,000 patients?

Answer: Case-control study

Case-control studies start with the outcome (rare event) and look backward, making them efficient for studying rare adverse events.

What does the term 'intention-to-treat' (ITT) analysis mean?

Answer: All randomized participants are analyzed in the group they were assigned to, regardless of adherence

ITT analysis preserves randomization integrity by including all participants in their assigned groups, even if they did not complete or adhere to the assigned treatment.

A study reports an odds ratio of 0.5 for a drug compared to placebo. How should this be interpreted?

Answer: The drug is associated with 50% lower odds of the outcome

An OR of 0.5 means the odds of the outcome in the drug group are half (50% lower) compared to the placebo group.

Which allocation concealment method best prevents selection bias in an RCT?

Answer: Centralized randomization via a telephone or web system

Centralized randomization systems are inaccessible to enrolling investigators, providing the strongest protection against selection bias.

In a clinical trial, a 'surrogate endpoint' is best described as:

Answer: A biomarker intended to predict a clinical outcome

Surrogate endpoints are biomarkers (e.g., HbA1c, tumor size) used as stand-ins for clinical outcomes, assumed to predict them.

What is the main limitation of an open-label extension (OLE) study?

Answer: Results are confounded because participants and investigators know the treatment

In an OLE, unblinding introduces performance and detection bias, making it difficult to attribute outcomes solely to the drug.