United Kingdom back pain exercise and manipulation (UK BEAM) trial: what happened to participants who were not included in analysis?

Editor—The UK BEAM Trial Team has produced a broad piece of research that has attempted to answer many questions about managing chronic back pain all at the same time.1 However, I find it difficult to understand how any conclusions can be drawn from the published results if 25% of the study population were not included in the analysis (23% at three months and 26% at 12 months). Knowing what happened to these participants would be helpful because any conclusions drawn from the remaining data without an intention to treat analysis severely weaken what is a brave piece of research.