Article review: extended commentary on a trial

Title: The effectiveness of a hyper-oxygenated fatty acid compound in preventing pressure ulcers
Authors: Torra i Bou J-E, Segovia Gomez T, Verdu Soriano J, Nolasco Bonmati A, Rueda Lopez J, Arboix i Perejamo M.
Journal: Journal of Wound Care 2005; 14(3): 117-121.
Introduction: Establishing whether an intervention is effective is best done by conducting a randomised controlled trial as other ways of ‘evaluating’ interventions are prone to biases which can mean that the conclusion is unreliable. Non-comparative study designs, such as
before and after’ studies can mislead as they cannot disentangle those changes in outcome which would have occurred over time regardless of the intervention being used. Measuring the area of a wound, applying an intervention, and repeating the measurement after some weeks, is an example of this type of study. In addition, the before and after studies may mislead due to ‘regression to the mean’, which occurs when a variable is measured in a group of people more than once. The net effect of this is that if mean values were high on initial measurement, then they are likely to be lower on a second measurement, and vice versa, making it appear as if a true change has occurred even if there is no true change in the parameters being measured.