From comparison to integration in health system change: bridging methodological silos in implementation science, quality improvement, biodesign, and comparative effectiveness research

Background Health systems increasingly draw on implementation science(IS), quality improvement(QI), Biodesign, and comparative effectiveness research(CER) to develop, evaluate, implement, and sustain improvements in care. Although each offers distinct methodological strengths, they are often applied separately, creating discontinuities across the health system change trajectory. Existing work has clarified their similarities and differences but offers limited guidance on how to integrate their complementary contributions in practice. Approach In this Perspective, we propose a phase-sensitive framework that organises methodological contributions according to the functional tasks of health system change rather than disciplinary ownership. The framework organises contributions from all four traditions across four recurring phases: (1) problem framing and system understanding; (2) solution design and selection; (3) evaluation and adaptation; and (4) embedding, sustaining, and scaling. Rather than assigning individual traditions to specific phases, it shows how their contributions can be selectively combined to meet each phase's methodological requirements. We illustrate its application using remote monitoring after hospital discharge for heart failure. Discussion The framework offers a conceptual structure for considering when and how to integrate complementary methods while preserving their distinct purposes and methodological strengths. Its utility and impact require empirical evaluation across diverse health system contexts. Conclusion Phase-sensitive methodological integration may provide a more coherent pathway from unmet clinical need to effective, equitable, and sustainable health system change.