A randomized controlled trial, process and economic evaluation, comparing multimodal care intervention to standard care for older adults in Mecklenburg-Western Pomerania, Germany: study protocol of the intensified interprofessional outpatient therapy for geriatric patients (InATheGer) model

Background Geriatric patients with multimorbidity and functional impairments represent a rapidly growing population that requires coordinated outpatient care to maintain independence and quality of life. In Germany, particularly in rural regions, outpatient care is primarily delivered by family doctors and general practitioners within a fragmented system that often lacks sufficient interdisciplinary collaboration. This fragmentation limits access to comprehensive, continuous care. Multimodal, interprofessional interventions that integrate medical, therapeutic, and psychosocial support may improve functional outcomes and reduce hospitalizations in these populations. This study aims to evaluate the effectiveness and efficiency of a structured, multimodal, and interprofessional coordinated outpatient care model for geriatric patients. Methods This multicenter randomized controlled trial will enroll 540 geriatric patients aged 70 years and older across three regional outpatient centers (intervention centers) in Mecklenburg–Western Pomerania (MV), Germany. Participants will be randomized 1:1 to receive either standard care or the Intensified Interprofessional Outpatient Therapy for Geriatric Patients (InATheGer) intervention. The intervention group will participate in a 14-week interprofessional outpatient program, comprising 20 therapy days with multimodal therapy sessions coordinated by a trained care manager (“InA-Manager”). Assessments will be conducted at baseline (before randomization), 18 weeks, and 31 weeks post-baseline. The primary outcome measure is the improvement in mobility and functional independence 18 weeks post-baseline, measured by an adapted Functional Independence Measure (FIM). Secondary outcomes include change in quality of life (EQ-5D-5 L), medication use, healthcare utilization, and costs. A qualitative process evaluation will complement the trial to explore implementation and contextual factors. Discussion If the InATheGer model demonstrates clinical effectiveness and cost-effectiveness, it will provide policymakers and healthcare stakeholders with evidence to inform the development and scaling of coordinated, interprofessional outpatient care for geriatric patients. Broad implementation of this model within routine geriatric outpatient care could enhance functional independence and quality of life among ageing populations while improving healthcare system efficiency. Trial registration German Clinical Trials Register (DRKS) registration number DRKS00036229. Prospectively registered on 08 April 2025.