03 · What You Need to Know
Version Control Creates a Traceable History of the Study Plan
A version identifies which protocol you are talking about
A study can have several protocol documents over its lifetime. An initial draft may be revised after methodological review. Another version may incorporate ethics committee requirements. A later amendment may change recruitment, measurement, or another procedure.
A version identifier distinguishes these documents. A simple system might use labels such as Version 1.0, Version 1.1, and Version 2.0 together with dates. Another institution may prescribe a different convention.
There is no need to invent a complicated numbering system when the institution already has one. The essential requirement is that each controlled version can be identified unambiguously.
The version date and approval date are not necessarily the same thing
A protocol may be finalized by the research team on one date and approved by an ethics committee, sponsor, or other authority later. Those dates answer different questions.
The version date identifies the document itself. An approval date records an external decision about that document. If a study operates under formal oversight, retaining both can help establish which version was authorized for use and when.
Do not alter the version date merely to make it match an approval date unless the governing process explicitly requires that convention. Follow the documentation rules of the relevant institution.
Version control prevents different team members from following different plans
Version control has an immediate operational purpose. If researchers, data collectors, statisticians, collaborators, or multiple sites possess different protocol files, study procedures can diverge without anyone intending them to.
One site might use revised eligibility criteria while another continues using the earlier rules. One analyst may follow an updated outcome definition while another uses the original one. The resulting inconsistency can affect both study conduct and interpretation.
A controlled current version, together with clear communication of updates, helps ensure that everyone knows which protocol governs the study at a given time.
Change tracking preserves the distinction between the original plan and later decisions
This is where version control becomes methodologically important rather than merely administrative.
Suppose a protocol originally identifies academic writing self-efficacy as the primary outcome. After preliminary examination, researchers decide that another outcome produces a more interesting pattern and revise the protocol so that the new outcome appears to have been primary all along.
If the original protocol is overwritten, the history disappears. If versions are preserved, readers can distinguish what was planned before the relevant data were known from what changed later.
This distinction is one reason writing the study design down before data collection matters in the first place. The evidentiary value of prior documentation depends partly on preserving it.
An amendment is a change to the current protocol, not a replacement of history
Terminology varies across institutions and research settings, but a protocol amendment generally refers to a prospective change to the approved or current study plan. Depending on the context, an amendment might alter eligibility, recruitment, intervention procedures, outcomes, measurements, sample size, analysis, safety procedures, or other study elements.
For randomized trials, SPIRIT 2025 treats the protocol as a living document and recommends documenting how important protocol modifications will be communicated to relevant parties. Its explanation and elaboration further emphasizes maintaining a transparent audit trail across protocol versions.
The broader principle is useful beyond trials: when the plan changes, create a new identifiable state of the plan rather than editing the old record until the change becomes invisible.
Not every edit necessarily requires a major new protocol version
Correcting a spelling error is not methodologically equivalent to changing an eligibility criterion or primary outcome. Versioning systems often distinguish minor editorial revisions from substantive amendments, although the exact rules vary.
A practical internal convention might reserve a major version change for substantive methodological modifications and a minor version change for limited clarifications. But if an ethics committee, sponsor, regulator, journal, or institution defines versioning differently, its rules should govern.
| Type of change |
Example |
Why it matters |
| Editorial correction |
Correcting a typographical error without changing meaning |
Usually has little or no methodological consequence |
| Clarification |
Making an existing procedure more explicit without changing what is done |
May still require documentation so users know which text is current |
| Operational modification |
Adding a recruitment channel or changing a data collection procedure |
May affect implementation, participants, comparability, or approval requirements |
| Methodological amendment |
Changing eligibility, outcome definition, sample size, measurement, or primary analysis |
Can affect scientific validity and interpretation |
| Ethical or safety amendment |
Changing consent, risk mitigation, monitoring, or participant procedures |
Can affect participant protection and may require prior review or approval |
A useful change record explains more than what changed
Knowing that a sentence was modified is not always enough. For consequential changes, the record should make it possible to understand the methodological history.
Depending on the study and applicable requirements, useful information can include the old and new version identifiers, dates, description of the change, reason for the change, person or body authorizing it, relevant approval status, implementation date, and whether data collection or access to relevant results had already occurred.
What changed? Identify the affected protocol section, procedure, criterion, outcome, analysis, or other element.
Why did it change? Record the scientific, ethical, operational, regulatory, or other reason.
When was the decision made? Record the date and, where methodologically relevant, the stage of the study.
Who authorized or approved it? Identify the responsible investigator, committee, sponsor, institution, or other authority when applicable.
When did it take effect? Distinguish the decision or approval date from the date on which the revised procedure was implemented when necessary.
Timing is particularly important for data-dependent changes
A methodological change made before any relevant data exist has a different interpretive context from the same change made after researchers have examined outcome patterns.
That does not mean the later change is automatically invalid. Perhaps the original analysis is inappropriate, an assumption fails, or an unforeseen data-quality problem becomes apparent. The correct response may be to change the method.
The record should make the timing visible. This supports the distinction between decisions fixed before data collection, planned flexibility, and decisions introduced after new information became available.
Version control should extend to important associated documents
The protocol is rarely the only study document that changes. Participant information sheets, consent forms, questionnaires, interview guides, statistical analysis plans, data-management plans, recruitment materials, manuals, and case-report forms may also be revised.
If those documents affect study conduct, they should be identifiable and linked to the appropriate protocol or approval state. Otherwise, a protocol may specify one procedure while the questionnaire or consent form implements another.
WHO's protocol guidance treats instruments, informed-consent materials, data management, analysis, and other supporting information as integral parts of protocol documentation for research within its remit. Keeping these materials synchronized is therefore part of maintaining a coherent study record.
Do not confuse an amendment with a protocol deviation
The terms are sometimes used differently across regulatory and institutional settings, so local definitions should be checked. Conceptually, however, a useful distinction can be made.
Protocol amendment
A documented change to the study plan, ordinarily made prospectively through the applicable change-control and approval process.
Protocol deviation
A departure from the protocol that occurs during study conduct rather than a prospective revision of the plan.
Not every deviation should be solved by retrospectively editing the protocol. Doing so would erase the fact that actual conduct differed from the plan in force at the time.
Formal approval requirements depend on the study
Researchers should not assume that every protocol change can be implemented immediately after updating the file. Studies subject to ethics, regulatory, sponsor, or institutional oversight may require review or approval of substantive amendments before implementation, except where governing rules permit or require immediate action.
WHO requires research involving human participants that it supports to undergo ethics review and provides specific submission guidance for research protocols and associated documents. Other institutions and jurisdictions have their own processes.
Always verify the requirements governing the particular study rather than treating a generic version-control practice as authorization to change an approved protocol.
Watch Out
Never solve a protocol inconsistency by silently editing the old file until it matches what the study eventually did. That produces a cleaner document but a poorer research record. Preserve the earlier version and document the change.
