Process evaluation of a case management intervention for people at high risk of permanent work disability to improve rehabilitation coverage and work participation

German social law provides a broad range of services aimed at maintaining work ability, facilitating return-to-work, and preventing permanent work disability; however, individuals with health impairments often lack information about available options and access, leading to underutilization of these services. This study (trial registration: DRKS00024648) evaluates the implementation of a multicomponent strategy designed to improve access to rehabilitation services and promote sustained work participation among individuals at elevated risk of permanent work disability. The intervention consisted of screening, postal contact, telephone counseling, initial interview, and case management. High-risk individuals were identified through a risk score based on administrative data (≥60 points indicating an increased 5-year probability of disability pension) and were invited by postal mail to call their regional case manager if support was required. Within the process evaluation, we assessed reach, dose delivered, fidelity, dose received, and participant satisfaction using case manager documentation and participant surveys at baseline and follow-up. Of 5300 individuals contacted, 277 engaged in case management. At baseline, participants reported an average of 20 weeks of sickness absence, multiple health conditions, and 63.7% rated their work ability as poor. Implementation fidelity exceeded 80%, and satisfaction with the intervention was high. Following case management, knowledge of rehabilitation services increased significantly ( P  < 0.001), and 55.6% applied for rehabilitation. The findings demonstrate that the intervention successfully reached its target population with high fidelity and participant satisfaction. Observed improvements in knowledge and increased utilization of rehabilitation services suggest the intervention's potential to enhance access for those in need.