Exploring Stakeholder Involvement in Intervention Implementation Studies: Systematic Evidence Synthesis With an Evidence Gap Map Approach.

Stakeholder involvement (SI) is essential for effective and sustainable intervention implementation, yet practical guidance is lacking. This study mapped SI use in implementation science studies, identified gaps, and proposed a practical framework for improved SI planning. Using an evidence gap map approach, this study built on Mielke et al.'s (2022) methodology, which identified implementation studies from 2015-2020. The search was updated to include studies from 2021-2023 from PubMed, using the same search strategy and inclusion criteria. Data extraction followed the Guidance for Reporting on Involvement of Patients and the Public reporting checklist. From 10,184 studies, a random sample of 2,005 was screened, adding 162 implementation science studies to Mielke et al.'s 110, totaling 272 studies for SI analysis. SI was reported in 89% of studies, but often lacked depth and strategic planning. Stakeholders were mainly engaged during the preparatory phase. Most studies involved micro- and meso-level stakeholders, rarely including macro-level stakeholders. Few described stakeholder selection or preparation. SI was mostly consultative, via interviews, surveys, and focus groups, with limited active collaboration. SI processes and costs were rarely evaluated. Our findings underscore the need for structured, comprehensive SI planning and offer practical recommendations to strengthen SI efforts in implementation research.