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A multiregional plan needs more than participant quotas assigned to countries. E17-focused preparation makes assumptions about treatment practice and measurement visible before recruitment, so the team can assess how regional differences could affect interpretation of the combined result.
Justify the regional grouping
ICH E17 addresses planning and design principles for multiregional clinical trials. Do not define regions solely by geographic proximity. Bring intrinsic and extrinsic factors affecting response, clinical practice and relevant regulatory needs into the design discussion before the proposed grouping becomes an operational commitment.
Record similarity assumptions
Use an assumption table to show differences in diagnosis, previous therapy, standard care, dose and endpoint assessment. Identify evidence supporting expected similarity. Do not base sample allocation or pooling decisions only on recruitment speed, as an operationally convenient distribution may leave important scientific questions inadequately addressed.
Check operational consistency
Seek consistency in training, language versions of measurement instruments and laboratory methods. A shared SOP does not establish that local practice is equivalent. Pilot records or example assessments can reveal that the same clinical concept is recorded differently across countries even when sites received identical central instructions.
- Support proposed pooling assumptions with relevant evidence.
- List differences in standard care and measurement.
- Document the scientific rationale for sample allocation.
Interpret regional results proportionately
Interpret regional treatment estimates alongside sampling uncertainty and the planned consistency assessment. Do not automatically expect independent statistical significance in every subgroup. Preserve the prespecified interpretive approach and have clinical, statistical and operational teams examine reasons for differences or departures together before drawing conclusions about regional acceptability.
Frequently asked questions
- Is a region simply a country or continent?
- Justify grouping using the design purpose and relevant factors; geography alone may be insufficient.
- Must every region show a significant result separately?
- There is no such general rule; assess the planned analysis and its uncertainty.