C: alternative experimental designs
6 important questions on C: alternative experimental designs
What are pilot or feasibility trials
- Aim is to assess the feasibility of methods and procedures intended to be used in a larger scale study
- Feasibility
- Randomisation
- Assessment
- Acceptability and feasibility
- NOT used for hypothesis testing
- Could be used for sample size calculation
What is a cluster randomised trial
- Randomisation at level of cluster (e.g. Practice, hospital) and not at level of individual patient
- Outcome measurement at level of individual patient
- Advantages in case of:
- Intervention aimed at cluster level (e.g. Department)
- Difficult for HCP's to switch between treatment
- Conamination
- Risk of bias less straightforward
- RoB at cluster level (baseline imbalance, selective drop out)
- RoB at individual level (differential individual recruitment or differential consent procedures
What are some issues to take into consideration regarding cluster randomised trial
- Unit of randomisation may be (too?) small for true randomisation
- Patients are 'clustered' (e.g. In GP practice) the sample size calculation needs to take that into account
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Non-inferiority trial (NI)
- A NI trial seeks to determine whether a new treatment is not worse than a reference treatment by more than an acceptable amount
- Because proof of exact equivalence is impossible, a restated margin of NI (triangle) for the treatment effect in a primary patient outcome is defined
- Equivalence trials are very similar, except that equivalence is defined as the treatment effect being -(triangle) and +(triangle)
What are some issues w/ non-inferiority trial (NI)
- Is the gain (e.g. Less burden ) of the new treatment a real gain?
- Choice appropriate comparator (at least not placebo)...
- Current treatment is better then placebo
- Determining NI margin (triangle) is a challenge
- ITT vs per protocol analyses
- In sum: interpretation is not straightforward
Phase I to IV trials: how interventions develop into mature interventions
- Phase 1: After promising findings w/ animal experiments -> healthy volunteers
- Phase 2: For first time relevant patients are targeted -> assess safety and optimal dose -> focus on intermediate outcomes
- Phase 3: Focus on real life situations with real patients
- Phase 4: postmarketing (surveillance) mainly to detect rare side effects
The question on the page originate from the summary of the following study material:
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