Abstract
BACKGROUND: The cluster randomized controlled trial interprof ACT evaluated the effects of a complex intervention designed to improve collaboration between general practitioners (GPs) and registered nurses (RNs) in nursing homes (NHs). The intervention includes six components (“Name badges”, “Mandatory availability rules”, “Designated contact persons”, “Standardized GPs’ home visits”, “Pro re nata medication”, “Shared goal setting”). The findings showed a nonsignificant reduction in hospital admissions in the intervention group (IG) compared to the control group (CG) within twelve months. The aims of this process evaluation were to describe (1) the dose, reach and fidelity of implementation (“implementation performance”), (2) the effects on the quality of RN-GP collaboration, and (3) potential moderating factors. METHODS: Process evaluation with a mixed-methods triangulation design involving all clusters (17 NHs per IG and CG) and 323 nursing home residents (NHRs) (n = 166 IG, n = 157 CG): We collected quantitative and qualitative data from multiple perspectives (e.g., RNs, GPs, NHRs) at several measurement points. We quantitatively compared groups by means of medians, interquartile ranges, proportions (all outcome domains) or Mann‒Whitney U tests (implementation performance) and analyzed qualitative data inductively via content analysis. The key findings were triangulated narratively and via a joint display. RESULTS: Compared to those in the CG, we noted relevant improvements in the implementation of “Name badges”, “Mandatory availability rules”, “Designated contact persons” and “Pro re nata medication” in ≥50% of the IG clusters, of which the group difference for “Mandatory availability rules” reached statistical significance. The implementation performance of IG clusters was moderated by resource-related and other organizational attributes of NHs and GP offices and attributes of involved professionals, especially their attitudes and awareness. Implementation of the components induced greater standardization of care processes together with positive changes in interprofessional communication and coordination among GPs and RNs. CONCLUSIONS: Implementation of the interprof ACT components varied between components and NHs but showed potential for improving RN-GP collaboration. The standardization of shared care procedures emerged as a key mediator for improvement. For larger and more sustainable implementation we recommend a stronger focus on locally available resources and communication of potential benefits for all involved parties. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03426475; registered 07 February 2018, https://www.clinicaltrials.gov/study/NCT03426475?lead=NCT03426475%26;rank=1. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12913-026-14270-2.