Laboratory practice
Randomization and Blinding in Laboratory Assays
Randomization and blinding: At which decisions was the opportunity for bias reduced?
Source editorial review:
Before interpreting the result
At which decisions was the opportunity for bias reduced?
- Record the allocation rule and the unit receiving the intervention.
- Identify who knew the groups during preparation, measurement and analysis.
- Keep blocks, batches and processing order to reconstruct the design.
Randomization and blinding
Random allocation and blinding address different bias sources. Allocation organizes how conditions are distributed; blinding limits information that could affect execution or interpretation. Neither repairs an unsuitable method by itself. Appraisal requires knowing when they were applied, to which units, and whether allocation became known at later stages.
A reading case: what to check
If every sample from one condition is measured first and the others last, order can become confounded with system changes. Check how the design handled this and who knew labels during analysis. If undescribed, record missing information rather than assuming bias protections were either present or absent.
What to preserve in the record
Writing 'random' or 'blinded' does not document the entire process. Describing specific decisions and stages reveals where an opportunity for bias remained.
Questions and answers
At which decisions was the opportunity for bias reduced?
Random allocation and blinding address different bias sources. Allocation organizes how conditions are distributed; blinding limits information that could affect execution or interpretation. Neither repairs an unsuitable method by itself. Appraisal requires knowing when they were applied, to which units, and whether allocation became known at later stages.
What should the review record preserve?
Writing 'random' or 'blinded' does not document the entire process. Describing specific decisions and stages reveals where an opportunity for bias remained.