As suggested by an African proverb from the Ashanti people in Ghana “You never test the depth of a river with both feet“, the main goal of pilot studies is to assess feasibility so as to avoid potentially disastrous consequences of embarking on a large study - which could potentially “drown” the whole research effort. (Thabane et al 2010)
Criteria for success need to be developed before the start of the pilot in order to determine whether it is feasible to continue into the main study. If modifications to the protocol are needed, make sure to note the necessary changes in your electronic logbook.
- Make sure each member of the project group considers the need of a pilot study;
- Clearly document decisions while undertaking the pilot study;
- Undertake a pilot study as you are performing the larger scale study.
- Consider the need of a pilot study;
- Support the executing researcher in undertaking the pilot study.
Research assistant: N.a.
In 2010, Thabane et al. published a tutorial on pilot studies. This handbook chapter was largely based on their work, please make sure to check the full article should you need additional information.
A pilot is usually conducted to test feasibility objectives, reasons for conducting a pilot study can be classified into 4 categories:
- Process: to test the feasibility of the separate steps of the study. For example; What are the anticipated number of participants? Are all medical files retrievable?
- Recourses: to test the time and budget problems that may occur. For example; Can all measurements be easily implemented? How long does it take to complete a questionnaire? Is the used software compatible with the data?
- Management: to test people and data management. For example; How long does a measurement take? How many measurements can be undertaken in one day? Are there any capacity issues?
- Scientific: to test the safety of treatments and the quality of the data. For example; Are all medical files retrievable? Have all the necessary details been registered in statuses? and is the quality of the data adequate?
Sample size of a pilot study
The sample size of a pilot study should be large enough to provide useful information about the aspects that are being assessed for feasibility (Thabane). Pilot studies may precede larger studies and may include a clear go/no go decision. The outcome of the pilot can be one of the following:
- Stop – target study not feasible
- Continue, but modify protocol – feasible with modifications
- Continue without modifications but monitor closely – feasible with close monitoring
- Continue without modifications – feasible as is
If the data are to be used for the target study, it is important that the population and in/exclusion criteria are the same. But beware that your decision to not change your protocol is not driven by your wish to include participants in the target study.