Patient and public involvement in clinical trials to improve outcomes for adults with multimorbidity in primary care and community settings: A systematic review protocol

Background Patient and public involvement (PPI) in clinical trials for adults with multimorbidity (multiple long-term conditions) in primary care is essential to ensure research is person-centred. However, PPI is often underreported, limiting understanding of its application and impact. This protocol describes a systematic review examining the uptake, impact and reporting quality of PPI in clinical trials of interventions to improve mental health, clinical or quality-of-life outcomes for adults with multimorbidity in primary care. Methods The review will be guided by the Cochrane Handbook and reported according to PRISMA-P guidelines. Eligible studies include completed and ongoing randomised and non-randomised controlled trials. Multimorbidity is defined as the co-existence of two or more long-term conditions. Electronic databases (MEDLINE, CINAHL, Embase, Cochrane) will be searched from 2019 to update Smith et al. (2021) without language restrictions. Trial registries and grey literature will identify protocols and supplementary data. Inclusion criteria - Population: adults with multimorbidity; Interventions: targeted at this population; Comparison: usual care; Outcomes: mental health, clinical or quality-of-life; Setting: primary or community care. Studies will be included irrespective of whether PPI was reported. Data extraction will capture PPI presence, characteristics, activities, training and acknowledgement. A narrative synthesis will describe reported PPI in clinical trials. Two PPI partners will contribute throughout the review. The protocol is registered with PROSPERO (CRD420251090082). Discussion/Conclusion This review will enhance understanding of PPI in trials aiming to improve outcomes for adults with multimorbidity in primary and community care, identify gaps in reporting, and inform future trials to support person-centred research.