Continuous outcome measures: conundrums and conversions contributing to clinical application

Many patient-relevant outcomes, particularly quality of life measures such as pain or function, are routinely measured on a continuous scale. However, the interpretation of continuous outcomes is difficult, particularly when considering application to clinical practice and shared decision-making. Making matters worse is the frequent existence of multiple scales for any given construct. Therefore, quantitative syntheses of literature must find a way to combine different scales into a 'common language', and the most frequently used and longest-standing method to do so is the standardised mean difference. Unfortunately, the standardised mean difference is even more difficult to interpret clinically. However, there are validated methods to make these measures easier to understand and apply clinically. This analysis explores these issues and offers a resource to help make these continuous measures more clinically useful.