Introduction The PRIME-UK randomised controlled trial (RCT) aims to establish whether a model of care that seeks to be proactive, integrated and empower participants, caregivers and healthcare professionals can improve outcomes in people with parkinsonism. Given that this intervention is novel and complex, understanding whether and how the intervention will be acceptable, implementable, cost effective and scalable across contexts are key questions beyond that of whether ″ it works ″. We describe an embedded process evaluation to answer these questions, which aims to support interpretation of the trial results, refinement of the intervention and support future scaling of the PRIME-Parkinson model of care. Methods and analysis A mixed methods approach will be used to collect data across four process evaluation domains: implementation, mechanism of change, acceptability and context. Quantitative data will be collected prospectively from all participants and analysed descriptively with exploratory tests of relationships as power allows. Qualitative data will be collected through semi-structured interviews with a purposively sampled sub-population of participants, caregivers and staff members as well as case studies where relevant. Interview transcripts will be analysed thematically using interpretive qualitative analysis. Synthesis of quantitative and qualitative data will also be performed to draw conclusions. Ethics and dissemination The quantitative data will be collected as part of the main PRIME-UK RCT which was been granted NHS REC approval (21/LO/0387) on 27th July 2021. The qualitative data will be collected as part of a sub-study, ′ PRIME-Qual ′, which was granted NHS REC approval (21/LO/0388) on 14th July 2021. The mixed methods process evaluation will be published after the conclusion of the trial in addition to the main trial findings.

KL is in receipt of PhD fellowship funding from The Gatsby Foundation and funding from Parkinson ′s UK. ET is funded by a National Institute for Health and Care Research Academic Clinical Lectureship and has received a speaker honorarium from the Neurology Academy. HB and SR are partly funded by National Institute for Health and Care Research Applied Research Collaboration West (NIHR ARC West) and The Gatsby Foundation. EJH is HEFCE funded by University of Bristol for her academic work and has received research funding from the National Institute of Health Research (NIHR), The British Geriatrics Society, The Gatsby Foundation, The Alzheimer ′ s Society, Royal Osteoporosis Society, The Dunhill Society, Parkinson ′ s UK. She has received travel support, honoraria and / or sat on advisory boards for Kyowa Kirin; Abbvie; Luye; the CME institute, Ever, Simbec Orion, the Neurology Academy and Bial. YBS is partly funded by National Institute for Health and Care Research Applied Research Collaboration West (NIHR ARC West) and University of Bristol, and has received funding from Parkinson ′ s UK, Royal Osteoporosis Society , MRC, HQIP, Templeton Foundation, Versus Arthritis, Wellcome Trust, National Institute of Health Research, Gatsby Foundation. JK and SS have no conflicts of interest FL is funded by the High Value Nutrition National Science Challenge, New Zealand, Health Research Council, New Zealand and the University of Auckland, New Zealand. This research was supported by the National Institute for Health and Care Research Applied Research Collaboration West (NIHR ARC West). The views expressed in this article are those of the author(s) and not necessarily those of the NIHR or the Department of Health and Social Care.

NCT05127057

This work was supported by The Gatsby Foundation grant number [GAT3676]

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The quantitative data will be collected as part of the main PRIME-UK RCT which was been granted NHS REC approval (21/LO/0387) on 27th July 2021. The qualitative data will be collected as part of a sub-study, ′ PRIME-Qual ′, which was granted NHS REC approval (21/LO/0388) on 14th July 2021. The mixed methods process evaluation will be published after the conclusion of the trial in addition to the main trial findings.

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Access to the data will be available through application to the Chief Investigator. Pseudo-anonymised data may be shared with other researchers to enable knowledge synthesis.