The ideas for clinical studies are generally based on previous research work. However, established interventions often need to be investigated for a newer indication or newer methods/interventions for a clinical procedure/condition. In such cases, researchers often face the dilemma, “Can I do this study?” A pilot study would help researchers while designing the study. This editorial aims to highlight the importance of a pilot study and encourage its use in pain medicine research.
The pilot study is often synonymously used with a feasibility and exploratory study. However, epidemiologically, they are different. Pilot studies are small-scale tests of the methods and procedures to be used on a larger scale if the pilot study demonstrates that these methods and procedures can work. Exploratory studies are usually even more preliminary than pilot studies and target identifying preliminary facts/problems, often without clear hypotheses. On the other hand, feasibility studies are more related to the practicability of the tested health program/interventions/procedure so that it can be implemented at a larger scale.[1]
UTILITY OF PILOT STUDIES
A pilot study identifies protocol flaws and helps researchers and participants, thus avoiding wasting time, money, and effort. Pilot studies are not only limited to randomized controlled trials but are also applicable to other types of study designs, including observational or epidemiological studies.[2,3] A pilot study evaluates the process of screening, recruitment, randomization, retention of participants, blinding, and adherence/reliability to the treatment protocol. The recruitment rates and the time required for informed consent can be assessed and modified if not feasible.
The pilot study also helps us to assess the data management plan, including data collection tools, documentation, and reporting procedures. The data management plan is critical, especially when the planned research design is multicentric. The pilot study ensures the study team follows good clinical practice by acquiring experiences, competencies, and skills required for accuracy and precision.[3,4]
SAMPLE SIZE CALCULATION, EFFECT SIZES AND OUTCOMES IN PILOT STUDIES
The pilot study does not need formal sample size calculation. However, the size of the participants’ population is based on pragmatic considerations so that the results can guide the researcher for large-scale studies in the future. The methods may include but are not limited to participant flow, availability of budget, and the number of participants needed for the study.
The main aim of any pilot study should be to assess the methods/processes of the proposed study design. However, proposed pilot studies often focus on inappropriate outcomes, such as efficacy assessment and intervention safety/tolerability.[5] The estimated effect sizes from pilot studies are imprecise due to the lesser sample size, which is reflected in the confidence limits. Pilot studies are not powered enough to conclude the efficacy of intervention due to the smaller sample size. Hence, pilot studies should not be used to assess the efficacy of an intervention.
Pilot studies are often conducted to obtain the effect size for sample size calculation for the main study. However, due to the imprecise nature of the effect sizes of pilot studies, sample size estimation using estimates from pilot studies should be avoided. Estimates from already published literature should be utilized for sample size calculation. In case published studies are not available, sample size estimation should be done with caution.
Descriptive statistics with appropriate measures of dispersion (95% confidence intervals/medians/means, as applicable) should be reported in pilot studies. Inferential statistical tests should not be applied while analyzing the data of pilot studies. However, control groups should be included in the pilot study if future studies aim to test the hypothesis. It will ensure the acceptability of methods/processes related to sampling, selection, and recruitment of the control group.[4,5]
Since the main objective of pilot studies is to assess the methods/process on a smaller scale before large-scale studies, the direct outcome of pilot studies should be reported as follows: (1) Researchers cannot proceed with the main study; (2) Researchers can proceed with the main study after some modification; (3) Researchers can proceed with the main study. However, close monitoring is required throughout the study; and (4) Researchers can proceed with the main study without modification.[5,6]
ETHICAL ISSUES AND FUNDING RELATED TO PILOT STUDIES
The good clinical practice guideline does not mention specific ethical issues related to the pilot studies. However, all ethical principles involving human research must be considered in the pilot studies with human participants.
Recently, funding opportunities for pilot studies have also been increasing. Some funding agencies have specific call-for-proposals for pilot studies limited to a shorter period (1–3 years). It helps avoid large-scale and expensive studies/trials, thus reducing the budget and duration of studies.[6]
A pilot study provides essential information about methods/processes before a large-scale study, such as the recruitment process, consent procedure, randomization, allocation, feasibility, and adherence to treatment/intervention. It minimizes the unnecessary wastage of time, resources, and effort from the researchers and participants.
REFERENCES
1. Porta M A Dictionary of Epidemiology 6th ed New York Oxford University Press Publisher 2014 103–215.
2. Teresi JA, Yu X, Stewart AL, Hays RD. Guidelines for designing and evaluating feasibility pilot studies. Med Care 2022;60:95–103.
3. In J. Introduction of a pilot study. Korean J Anesthesiol 2017;70:601–5.
4. Leon AC, Davis LL, Kraemer HC. The role and interpretation of pilot studies in clinical research. J Psychiatr Res 2011;45:626–9.
5. Arain M, Campbell MJ, Cooper CL, Lancaster GA. What is a pilot or feasibility study?A review of current practice and editorial policy. BMC Med Res Methodol 2010;10:67.
6. Thabane L, Ma J, Chu R, Cheng J, Ismaila A, Rios LP, et al. Atutorial on pilot studies:The what, why and how. BMC Med Res Methodol 2010;10:1.
