CCDM Clinical Trial Design 2 — Questions and Answers
Question 1: In a crossover trial design, what is the primary purpose of a 'washout period'?
- To recruit additional participants
- To eliminate carryover effects from the previous treatment (Correct answer)
- To collect baseline laboratory data
- To train site staff on new procedures
Correct answer: To eliminate carryover effects from the previous treatment
A washout period allows the effects of the first treatment to dissipate before participants receive the next treatment, preventing carryover bias.
Question 2: Which allocation concealment method is considered the gold standard in randomized controlled trials?
- Sealed opaque envelopes
- Alternating assignment by enrollment order
- Centralized randomization via IVRS/IWRS (Correct answer)
- Assignment based on birth date
Correct answer: Centralized randomization via IVRS/IWRS
Centralized randomization via Interactive Voice/Web Response Systems (IVRS/IWRS) provides the most robust allocation concealment because the randomization sequence is controlled remotely.
Question 3: A Phase II dose-finding trial using a '3+3 design' is primarily used to determine which of the following?
- Efficacy compared to placebo
- Maximum tolerated dose (MTD) (Correct answer)
- Long-term safety profile
- Pharmacokinetic bioavailability
Correct answer: Maximum tolerated dose (MTD)
The 3+3 design is a traditional dose-escalation method used in oncology Phase I/II trials to identify the maximum tolerated dose based on dose-limiting toxicities.
Question 4: What distinguishes an 'adaptive trial design' from a conventional fixed design?
- It uses a larger control group throughout
- It allows pre-specified modifications based on interim data (Correct answer)
- It eliminates the need for a statistical analysis plan
- It requires no IRB oversight for modifications
Correct answer: It allows pre-specified modifications based on interim data
Adaptive designs permit pre-specified modifications to trial parameters (e.g., sample size, dose, population) based on accumulating interim data without compromising validity.
Question 5: In a factorial trial design, two experimental treatments A and B are tested simultaneously. What is the main statistical advantage?
- It requires twice as many participants
- It can evaluate both treatments and their interaction in a single trial (Correct answer)
- It eliminates the need for randomization
- It is only suitable for Phase I trials
Correct answer: It can evaluate both treatments and their interaction in a single trial
Factorial designs allow evaluation of the individual and combined effects of two or more interventions within a single study, improving efficiency.
Question 6: Which trial design is most appropriate when blinding participants and investigators is impossible due to the nature of the intervention?
- Double-blind randomized controlled trial
- Open-label trial (Correct answer)
- Triple-blind trial
- Placebo-controlled crossover trial
Correct answer: Open-label trial
Open-label trials are used when blinding is not feasible, such as with surgical interventions or behavioral therapies, though they carry a higher risk of performance bias.
Question 7: A non-inferiority trial is designed to show that a new treatment is:
- Superior to the active comparator in efficacy
- Not worse than the active comparator by more than a pre-specified margin (Correct answer)
- Equivalent to placebo in safety
- Different from the control with no defined boundary
Correct answer: Not worse than the active comparator by more than a pre-specified margin
Non-inferiority trials aim to demonstrate that a new treatment's efficacy is not worse than a reference treatment by more than a clinically acceptable margin (delta).
CCDM Clinical Trial Design 2
In a crossover trial design, what is the primary purpose of a 'washout period'?