The importance of outcomes in research

‘Clinical trials are only as credible as their outcomes.’1

Clinical trials guide clinical practice. They do this by demonstrating beneficial or detrimental effects of an intervention on patients: the outcomes of the trial. The reliability of trial findings can be reduced by poor research practices such as inadequate allocation concealment or lack of blinding.2 The CONSORT standards were developed to alleviate the problems caused by poor trial reporting.3 Problems can also be caused by the selection, measurement and reporting of outcomes for clinical trials:

• Heterogeneity: When trials addressing similar clinical questions measure different outcomes, or the same outcome at different points or using different tools, it is difficult to combine results in systematic reviews or meta-analyses. A recent study of neonatal Cochrane reviews demonstrated that half were inconclusive, with heterogeneity of outcomes an important contributor.4

• Selective reporting: Selective reporting of outcomes on the basis of the results is widespread.5 This can introduce bias to such a degree that after selective reporting is addressed, the conclusions of Cochrane reviews have been shown to change from evidence of benefit to no evidence of benefit.6 Preregistration of trials, and of the outcomes to be reported, is increasingly practised to minimise this.7

• Relevance: When the outcomes of a trial are not relevant to research users (patients, parents and clinicians) statistically significant results may be …