Multiple long-term conditions (MLTCs), commonly referred to as multimorbidity, are defined as the coexistence of two or more long-term conditions within an individual. The prevalence of MLTCs increases with age and is associated with polypharmacy, reduced quality of life, increased healthcare utilisation and costs, and poorer clinical outcomes. Research involving MLTCs is characterised by considerable heterogeneity in outcome selection and reporting, which limits the comparability, synthesis and interpretation of study findings. Core outcome sets (COS) provide an agreed minimum set of outcomes that should be measured and reported in all studies within a particular field and can improve the consistency, relevance and patient-centred focus of research.
This study aims to update and refine the existing Core Outcome Set for Multimorbidity (COSmm) through an international Delphi consensus process. Although COSmm represented an important step towards standardisation, its development was based on a relatively small sample (n=26), including limited patient and public representation (n=5). Furthermore, substantial work has subsequently been undertaken to improve the conceptualisation and operational definition of MLTCs, providing a stronger foundation for contemporary core outcome development.
Approximately 200 participants will be recruited, including researchers, healthcare professionals, people living with MLTCs and carers. Particular emphasis will be placed on ensuring meaningful representation from people living with MLTCs and carers, in response to priorities identified through our patient and public involvement and engagement activities. All outcomes included within COSmm will be retained within the initial outcome list and assessed alongside outcomes identified through subsequent research, evidence reviews and expert input. The study will additionally seek consensus regarding appropriate measurement instruments and assessment time points for outcomes included within the final COS, extending beyond the scope of previous multimorbidity COS studies.
The proposed work differs from existing multimorbidity-specific COS initiatives that focus on particular populations, settings or intervention types, as it seeks to establish an updated generic COS applicable across the broader MLTC research landscape. The study is being undertaken in collaboration with members of the original COSmm team. The resulting COS will support greater consistency, comparability and relevance in future MLTC research and facilitate the generation of evidence that is meaningful to patients, carers, clinicians and researchers.
Prof Kamlesh Khunti - University of Leicester
Dr Patrick Highton – University of Leicester
Dr Viet-Hai Phung – University of Leicester
Dr Ashkon Ardavani - University of Leicester
Dr Arron Peace - University of Leicester
Dr Mark Funnell - University of Leicester
Prof Laura Gray - University of Leicester
Professor Avan Sayer – Newcastle University
Disease Category: Other
Disease Name: Multimorbidity
Age Range: 18 - 120
Sex: Either
Nature of Intervention: Any
- Clinical experts
- Consumers (caregivers)
- Consumers (patients)
- Methodologists
- Patient/ support group representatives
- Researchers
- Service users
- Statisticians
- COS for clinical trials or clinical research
- Recommendations for outcome measures (measurement/how)
- Delphi process
This study will employ a modified Delphi methodology to update and refine the existing Core Outcome Set for Multimorbidity (COSmm) for use in research involving people living with multiple long-term conditions (MLTCs). The study has been designed to address limitations identified within COSmm, including its relatively small sample size and limited patient and public representation, while ensuring alignment with contemporary definitions and conceptualisations of MLTCs.
Approximately 200 participants will be recruited, comprising researchers, healthcare professionals, people living with MLTCs and carers. Recruitment will aim to achieve balanced representation across professional and lived-experience stakeholder groups, with approximately equal contributions from researchers and healthcare professionals and from people living with MLTCs and carers.
The initial outcome list will be developed from multiple sources, including the outcomes contained within COSmm, findings from subsequent relevant research, a review of the published literature and input from an expert steering group. Existing COSmm outcomes will be retained from the outset and evaluated alongside all other candidate outcomes to determine their continued relevance and importance within the contemporary MLTC research landscape.
Participants will score outcomes using a 9-point Likert scale across successive Delphi rounds. In Round 1, participants will rate the importance of each outcome and may suggest additional outcomes for consideration. In Round 2, participants will receive anonymised feedback on group responses and will be invited to re-score outcomes that have not reached consensus. A third Delphi round will be undertaken if further consensus is required.
Following agreement on the final core outcome set, expert recommendations regarding appropriate measurement instruments and assessment time points for each outcome will be developed. These recommendations will be subjected to an additional consensus exercise involving Delphi participants. This represents a substantive extension of previous multimorbidity COS studies, including COSmm, which did not formally establish consensus regarding outcome measurement or timing of assessment.
The study is being conducted in collaboration with members of the original COSmm development team to ensure continuity with previous work while addressing recognised methodological limitations and emerging developments within the field of MLTC research. This process will result in an updated and comprehensive COS intended for use across a broad range of MLTC research studies.