A core outcome set for trials evaluating self-management interventions in people with severe mental illness and coexisting type 2 diabetes.

Background: People with severe mental illness (SMI), such as schizophrenia, have higher rates of type 2 diabetes and worse outcomes, compared to those without SMI and it is not known whether diabetes self-management interventions are effective for people who have both conditions. Research in this area has been impeded by a lack of consensus on which outcomes to prioritise in people with co-existing SMI and diabetes.

Aims: To develop a core outcome set (COS) for use in effectiveness trials of diabetes self-management interventions in adults with both type 2 diabetes and SMI.

Methods: The COS was developed in three stages: (i) identification of outcomes from systematic literature review of intervention studies, followed by multi-stakeholder and service user workshops; (ii) rating of outcomes in a two-round online Delphi survey; (iii) agreement of final 'core' outcomes through a stakeholder consensus workshop.

Results: Seven outcomes were selected: glucose control, blood pressure, body composition (body weight, BMI, body fat), health-related quality of life, diabetes self-management, diabetes-related distress and medication adherence.

Conclusions: This COS is recommended for future trials of effectiveness of diabetes self-management interventions for people with SMI and type 2 diabetes. Its use will ensure trials capture important outcomes and reduce heterogeneity so findings can be readily synthesised to inform practice and policy.