January 14, 2021


Regular readers of the blog will know that we like to summarise a randomised clinical trial, where possible. We do this because they are the most reliable method of comparing the effectiveness of interventions fairly.

This short step is about looking at the method section of randomised trials.

Research methodologists and statisticians have developed an accepted formula for presenting clinical trial methods.  They have outlined this in the  CONSORT statement.

We think that this is an excellent reporting guide, but it is also a great learning resource. We produced an orthodontic version of this several years ago to help with orthodontic aspects of trial reporting.   Authors must include all of these points in a trial report. It is therefore difficult (and possibly inappropriate to cherry-pick from this), but I have nonetheless selected several vital points below:


It is essential that the authors clearly describe the participants. Ultimately, we need to know whether the findings from the study are relevant to our practice. Studies carried out in university settings involving non-paying patients, treated by students may, for example, be less applicable to seasoned practitioners in private offices. Similarly, one would have to question the validity (and generalisability) of undertaking a clinical trial relating to growth modification in adults!


We must consider outcomes relevant to both practitioners and patients to maximise the yield from onerous and expensive research studies. However, I will stop there as I know Kevin will consider this in more detail in a forthcoming post.

Sample size calculation:

Often, this is seen as the preserve of statisticians with mathematical minds that intimidate us; however, no randomised controlled trial is complete without one. Calculations should be undertaken before commencement and based on realistic estimates of what we feel are clinically-important between-groups differences. Adequate numbers are essential both to ensure that the study has sufficient power to identify meaningful differences and ensure that the investigation is credible.

Randomisation procedures:

These include both the generation of an unpredictable sequence and its subsequent implementation. A fundamental advantage of a randomised trial over, for example, retrospective studies is our ability to eliminate selection bias (to avoid the cherry-picking that I am guilty of right now). It is, therefore, essential that the process is transparent and performed carefully.

Statistical methods:

I will post about this in more detail soon. However, key messages are that statistics should be focussed and finite. Specifically, we must design our statistical approach to answer our key question (e.g. ‘Does the use of bracket A result in more efficient alignment of the lower anteriors than Bracket B?’) rather than undertaking a battery or analyses.

This short post is merely a potted summary of clinical trial methodology. You can garner lots more depth and explanation by accessing the CONSORT statement.

Next week we are going to look at randomisation and concealment in more detail.  You need to have a full understanding of these concepts if you are going to appraise a clinical trial.

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Padhraig Fleming
Professor of Orthodontics, Trinity College Dublin, The University of Dublin, Ireland

Have your say!

  1. Dear Padraigh, I have enjoyed this series and this article, congratulations. Personally, I would prefer statistical analysing in a non-binary basis to yield richer and more interesting insights of the data. So rather than (e.g. ‘Does the use of bracket A result in more efficient alignment of the lower anteriors than Bracket B?’) the result could be bracket A aligns ‘X’ amount faster than bracket B.
    My next comment may be in the next section, but it may be within this. Publication of the experimental method, and statistical methods should be made prior to starting the experiment. The more research is tied to a manufacturer or vested interest the more this needs to occur. And, to be critical of publishers … who do have some difficult decisions, all results need to be published.
    We need to lift our game.
    I look forward to the remaining papers in this series.

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