Table 1. ACP+ intervention components, intervention activities and materials (results of step 1, prior to evaluation of feasibility and acceptability).

Intervention component (n = 9)	Intervention activities (n = 16)	Intervention materials (n = 16)†
1 |ACP (external) Trainer	1. Selection and preparation of an (external) ACP Trainer, who provides adjusted support throughout stepwise implementation	1. Manual for ACP Trainer
2 | Engagement/ Buy-in of management	2. Meeting(s) between the ACP Trainer and the nursing home management, board of directors and coordinating advisory physician [46]*	2. ACP Information guide for nursing home management
3 | ACP Reference Persons	3. Selection of ACP Reference Persons 4. Two-day interactive training for the ACP Reference Persons, provided by the ACP Trainer	3. Training manual for two-day training
		4. ACP Manual for the ACP Reference Persons
4 | Information about ACP	5. Information (session(s)) for all care professionals, the coordinating advisory physician and the management 6. Information (session(s)) for all residents and their families about advance care planning and the policy/procedures in the nursing home	5. Invitation letter for staff, coordinating advisory physician and management for information sessions 6. Invitation letter for family physicians 7. ACP Information brochure for nursing home staff and family physicians 8. Invitation letter for residents and families 9. ACP information brochure for residents and family
	7. Information (session(s)) for all family physicians about advance care planning and the policy/procedures in the nursing home
5| Planned ACP conversations	8. Exploration of previously recorded wishes and family physician involvement 9. First advance care planning conversation according to the ACP Conversation Guide, with resident and family or family alone, if resident is not able to participate 10. Follow-up advance care planning conversations (yearly or after trigger moments such as admission to hospital or death of a relative) 11. Documentation of wishes and preferences on a standardized form (of which a copy is saved in the resident’s file), a summary sheet and ADs (if perceived necessary by the resident, or family if resident is not able to participate)	10. ACP Conversation Guide 11. ACP Document 12. Standardized Advance Directive documents
6 | In-house training	12. In-house training sessions (session 1 and session 2) to train nurses (and others such as clerical workers, moral consultants, social workers, etc.) who are willing to conduct advance care planning conversations (called ACP Conversation Facilitators) 13. In-house training session to train other staff (care workers, hairdressers, cleaning staff, administrative staff etc.) and volunteers to train them to recognize triggers in residents and family (called ACP Antennas)	13. Training manual for training other staff
7 | Multi-disciplinary meetings	14. Multidisciplinary meetings are held and the advance care planning process for each resident is discussed (the resident’s most important decisions, possible triggers for initiating advance care planning with residents and/or family and discussions still planned)	14. Summary sheet
8 | Reflection	15. Reflective (debriefing) sessions among all care professionals at the nursing home in which they discuss the death and advance care planning process of every resident who died during that month	15. Reflection instrument
9| Formal monitoring system	16. A formal monitoring system is put in place in which the nursing home evaluates advance care planning organization and procedures	16. Audit instrument

ACP advance care planning.

*Nursing homes are legally obliged to have at least one coordinating and advisory physician (remunerated according to the number of beds), who coordinates medical care in the facility, as well as reference nurses for palliative care (0.10 FTE per 30 residents).

†The source of and adaptations made to every intervention material is reported in the Supporting Information Materials (S1 Table).