Principle R2: Consistent and complete reporting

End of study reporting of participation changes should be done consistently within a study, showing any changes in level of participation, preferably split by treatment group.

This helps with the assessment of the quality of the study and of the reliability of the results. It can also inform the size, design and conduct of future studies.

Methods used to handle missing data should also be described, to allow interpretation and replication of results.

When reporting a study’s results, it is essential that researchers present the level of, and reasons for, missing data due to changes in participation. This helps the reader to assess the quality of the study and reliability of the results.

It should be clear what happened to all study participants, including whether they completed all aspects of the study or had to stop any of them early, including reasons why they stopped, where reasons are available.

The level of detail presented can depend on the nature and design of the study, as well as the format of the report, but should be enough to meet the aims described in this principle.

Adoption of this principle, in accordance with the Consolidated Standards of Reporting Trials (CONSORT) guidance, will help ensure consistency across studies.

If any participants stopped taking part in some or all aspects of the study before the end, this should be taken into account when analysing the study data. 

The analysis methods used should be reported, so that anyone reading the study results knows what has been done and why.

Complete reporting allows researchers planning future studies to learn how often and why participation changes during studies.

This means they can make evidence-based adjustments to sample size calculations and adjust their study design to improve participation.

Consistent and complete reporting allows other researchers to use the results for further research, for example in a ‘meta-analysis’, where results from several studies are combined to get an overall result.

See also:

Relevant PeRSEVERE resources:

Relevant PeRSEVERE principles:

  • Reporting of data on participation changes should be done in the knowledge that participation can stop, change or reduce. See principle O1 for more on this.
  • There should be separate data reported about participants who said they wanted to stop and those who lost contact with the research team. See principle O4 for more on this.
  • Clear reporting is reliant on good quality data collected during the study about participation changes. See principle M1 for more about this.
  • Treatment groups: many types of research study involve comparing groups of participants taking different treatments, to see which treatment which might be better.  
  • Missing data: data that was planned to be collected might not be included in a study analysis because researchers do not have access to it, or because it does not exist. All the planned data that is not included in study analysis is collectively called missing data.
  • Sample size: before a study starts, researchers need to work out the minimum number of participants they will need in order for the study to reach a clear conclusion. This number is called the sample size. The number should not be much more than this minimum number, because once there is a clear conclusion, people outside the study (that is, patients receiving routine healthcare) should benefit from the study results.