Making sense of trial results: outcomes and estimation

The format in which the results of randomised controlled trials (RCTs) are presented can have a major impact on how they are interpreted, and the extent to which they will be adopted into clinical practice. A key element in the reporting of RCTs is the measurement scale on which outcomes are assessed. Scales which are presented as large whole numbers tend to attract the interest of clinicians and patients, independent of the reliability of the estimates.1,2 Enough information needs to be presented to allow clinicians to convert the size of the reported benefit into a format which allows easy comparison with other relevant trial results, including the range of certainty of the benefit (Box 1).3 As outcomes may be measured and collected in a variety of ways, it is essential that there is prior agreement on how any benefit or detriment of the intervention will be reported.