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Ann Fam Med. 2018 Mar;16(2):132-138. doi: 10.1370/afm.2178.

A Core Outcome Set for Multimorbidity Research (COSmm).

Author information

HRB Centre for Primary Care Research, Department of General Practice, Royal College of Surgeons in Ireland (RCSI), Dublin, Ireland
HRB Centre for Primary Care Research, Department of General Practice, Royal College of Surgeons in Ireland (RCSI), Dublin, Ireland.
Centre for Academic Primary Care, NIHR School for Primary Care Research, School of Social and Community Medicine, University of Bristol, Bristol, United Kingdom.
Department of Health Sciences Research, Research Chair on Chronic Diseases in Primary Care, Chicoutimi (Quebec), Canada.
Institute for Health Research, Kaiser Permanente Colorado, University of Colorado School of Medicine, Denver, Colorado.
Département de médecine de famille, Université de Sherbrooke, Sherbrooke (Québec), Canada.



We aimed to develop a consensus-based set of core outcomes specifically for studies in multimorbidity.


We undertook a consensus study following the COS-STAR (Core Outcome Set-STAndards for Reporting) guidelines for the design and reporting of core outcome sets. A Delphi panel of experts completed a web-based survey with 2 rounds. Panelists were presented with a range of outcomes that had been identified in previous workshops and a related systematic review. They indicated their level of agreement on whether each outcome should be included in the core set using a 5-point Likert scale, and outcomes reaching a prespecified consensus level were included.


Of 30 individuals invited to be panelists, 26 from 13 countries agreed. All 26 completed both rounds of the survey. The Delphi panel reached consensus on 17 outcomes for inclusion in a core outcome set for multimorbidity (COSmm). The highest-ranked outcomes were health-related quality of life, mental health outcomes, and mortality. Other outcomes were grouped into overarching themes of patient-reported impacts and behaviors (treatment burden, self-rated health, self-management behavior, self-efficacy, adherence); physical activity and function (activities of daily living, physical function, physical activity); consultation related (communication, shared decision making, prioritization); and health systems (health care use, costs, quality of health care).


This consensus study involved a wide range of international experts who identified a large number of outcomes for multimorbidity intervention studies. Our results suggest that quality of life, mental health outcomes, and mortality should be regarded as essential core outcomes. Researchers should, however, also consider the full range of outcomes when designing studies to capture important domains in multimorbidity depending on individual study aims and interventions.


chronic disease; complexity; core outcome set; methodology; multimorbidity; primary care; research

[Indexed for MEDLINE]
Free PMC Article

Conflict of interest statement

Conflicts of interest: E.W. is Senior Research Fellow in the HRB Centre for Primary Care Research in Ireland (HRB grant HRC-2014-1); M.F. holds the Research Chair on Chronic Diseases in Primary Care, Université de Sherbrooke, Canada.

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