Footnotes

• We acknowledge the additional technical assistance with illustrations that was provided by Phillip Saunders, Unit Administrator, Department of Public Health (Health Services Research Unit), University of Oxford.

• Contributors: All the authors have considerable experience in developing, evaluating, and applying questionnaires for patients and are currently involved in long term multicentre trials where patient reported outcomes are the main end points. JD and AJC have chiefly worked in the area of patient reported outcomes in the context of orthopaedic surgery. HD is a senior statistician specialising in the development and application of patient reported outcome measures and on randomised controlled trials of complex interventions. RF has worked on both patient reported outcomes and patient experience of care relating to a wide range of conditions and interventions, both surgical and long term medical. CJ has worked on both patient reported outcomes and patient experience of care, the latter related to his work with the Picker Institute Europe, Oxford, UK. All authors contributed to the writing of this paper. JD is the guarantor.

• Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare (1) No financial support for the submitted work from anyone other than their employer; (2) No financial relationships with commercial entities that might have an interest in the submitted work; (3) No spouses, partners, or children with relationships with commercial entities that might have an interest in the submitted work; (4) No non-financial interests that may be relevant to the submitted work.

• Provenance and peer review: Commissioned, externally peer reviewed.