Background: Health care systems in Western countries are increasingly pressured by population changes and labor market shortages. In response, Dutch health authorities and interest groups agreed on a reform agenda in 2018. A key reform principle is 'the right care in the right place': the regional coordination of initiatives to prevent, substitute, or relocate health and support services across health and social care systems in order to better meet the needs of residents and to improve their functioning. However, diverging stakeholder perspectives on this reform challenges regional partnerships to select useful indicators to determine local needs and improvement areas. We therefore aimed to facilitate academic and field expert consensus, and propose useful indicator sets in supporting the regional discussion about delivering 'the right care in the right place'.
 Methods: Modified Delphi and nominal group techniques were used. Invited experts included representatives from interest groups (patients, vulnerable residents, and care professionals), knowledge institutes, regional partnerships, municipalities and private health insurers. First, from published international research about measures used in the context of population health management, researchers identified indicators, clustered them in themes, which they then pre-selected for potential relevance. Second, a web-survey and validated scoring methods were used to establish expert consensus about relevant themes. Third, experts voted on themes, discussed initial voting results, and – if desired – changed votes during online meetings. Fourth, for the 25 prioritized themes, researchers identified available indicators from data collections in the Netherlands. Fifth, another web-survey was used for expert voting on indicator usefulness per theme. Sixth, indicator sets were presented, and next steps were discussed with experts. During rounds 2-6, experts added indicators, shared arguments on their selections, or both. These qualitative data were thematically coded.
 Results: Contributions by 40 experts resulted in: 1) a base set with available indicators with the highest aggregated score for the 25 prioritized themes, 2) a ‘optional set’ with other ‘not-low-scoring’ indicators, and 3) an indicator development agenda. Amongst themes with the highest priority, those about structure (e.g., ‘collaboration across health and social care systems’) and processes (e.g., ‘inflow, throughflow and outflow within care chains’) generally received more votes than those about outcomes (e.g., ‘healthy weight’). Experts argued mostly against the usefulness of available indicators for the highest prioritized themes. Arguments raised were often about ability to influence the indicator or whether the indicator says something about multi-system developments, e.g., both in health and social care. For twelve themes, experts did not comment on the indicators chosen for the base- and optional-set.
 Learned lessons and next steps: Consensus techniques facilitated the establishment of common ground for selecting useful indicators about regional health and social care integration. Although available indicators appeared acceptable for almost half of the prioritized themes, open and routinely collected data provide limited opportunities to indicate integrative regional reform as stakeholders intend. Prioritized and accepted indicators will be made accessible in an existing online data tool. Execution of the development agenda starts with instrument development for indicating cross-system regional collaboration.