The critical role of mixed methods research in developing valid and reliable patient-reported outcome measures.

Randomised controlled clinical trials provide the gold standard for evidence underpinning clinical guidelines and patient centred care. However, this is only true when they are robustly designed, conducted and reported and then only if they include outcomes that are important to patients and clinicians. Important outcomes include those that measure impact on patient experience, quality of life, overall well-being, and physical, social, cognitive and emotional functioning, all of which require patient reported outcome measures (PROMs). Patient centred care must be underpinned by objective evidence of the effect of interventions on outcomes that are important to patients. Evidence for patient reported outcomes must be supported by valid and reliable PROMs. Importantly the PROM must reflect patient experience of the impact of the intervention on the outcome and enable quantitative evaluation of that impact. The purpose of this paper is to highlight the critical role of mixed methods research in developing PROMs that are valid (measure what they purport to measure), acceptable to those reporting the outcome and able to reliably detect meaningful differences between individuals with different conditions or severity and with time. This can only be achieved through a structured mixed methods program combining qualitative and quantitative research techniques.