Managing Incomplete Pilot Studies: Implications and Reporting Considerations
When subjects do not complete a pilot study, researchers must document these dropouts, analyze their impact on feasibility assessment, and include this information in their reporting to ensure valid conclusions about the main study's viability.
Understanding the Impact of Subject Non-Completion
Pilot studies serve a specific purpose - to assess feasibility rather than test hypotheses or determine efficacy. When participants don't complete a pilot study, this becomes critical information about the feasibility of the proposed research approach.
Documentation Requirements
According to CONSORT guidelines and best practices, researchers must:
- Document the number of participants who did not complete the study by group 1
- Record specific reasons for non-completion 1
- Calculate and report completion rates as part of feasibility assessment 1
- Include this information in the participant flow diagram 1
Impact on Feasibility Assessment
Non-completion in a pilot study provides crucial information about:
- Recruitment and retention feasibility - High dropout rates signal potential problems with the main study design 2
- Protocol acceptability - Participants may find interventions too burdensome or unacceptable 1
- Sample size calculations - Dropout rates must be factored into sample size estimates for the main study 3
- Resource requirements - Higher than expected attrition may indicate need for additional resources 1
Analyzing Patterns of Non-Completion
The SISAQOL consortium recommendations emphasize the importance of:
- Standardizing the definition of missing data 1
- Developing a standardized case report form to identify reasons for non-completion 1
- Comparing characteristics of completers versus non-completers 1
Key Analyses to Perform
When participants don't complete a pilot study:
- Compare baseline characteristics between completers and non-completers 1
- Identify potential predictors of dropout 1
- Assess whether dropout was related to the intervention itself 1
- Evaluate whether missing data was related to participants' health status 1
Implications for the Main Study
Non-completion in a pilot study should directly inform modifications to the main study:
- Protocol adjustments - May need to modify intervention intensity, duration, or delivery method 2
- Sample size recalculation - Must account for expected attrition rates 3
- Recruitment strategy changes - May need broader inclusion criteria or different recruitment approaches 4
- Data collection modifications - Consider less burdensome assessment methods 1
Common Pitfalls to Avoid
When interpreting pilot study results with non-completers:
- Don't ignore dropouts - They provide crucial feasibility information 1
- Don't treat pilot studies as hypothesis-testing - They are not designed to evaluate efficacy 5
- Don't generalize beyond inclusion/exclusion criteria - Feasibility results are context-specific 5
- Don't use pilot data for precise effect size estimation - Small samples produce imprecise estimates 5
Reporting Recommendations
The CONSORT guidelines specify that researchers should:
- Include a table documenting flow of participants through each stage 1
- Report numbers and reasons for non-completion by study group 1
- Discuss implications of dropout rates for main study feasibility 1
- Avoid making claims about efficacy or effectiveness 5
By properly documenting, analyzing, and reporting non-completion in pilot studies, researchers can make informed decisions about whether and how to proceed with the main study, potentially saving significant resources by identifying and addressing problems before full-scale implementation.