CC BY 4.0 Attribution 4.0 InternationalTeeling, Sean PaulBaldie, DeborahDaly, AilishPierce, AnthonyWolfe, NicolaFagan, GillianGarry, Catherine2025-09-122025-09-04Teeling, S.P., Baldie, D., Daly, A., Pierce, A., Wolfe, N., Fagan, G. and Garry, C. (2025) ‘Testing realist programme theories on the contribution of lean six sigma to person-centred cultures: a comparative study in public and private acute hospitals’, Hospitals, 2(3), p. 23. Available at: https://doi.org/10.3390/hospitals2030023.2813-4524https://eresearch.qmu.ac.uk/handle/20.500.12289/14402https://doi.org/10.3390/hospitals2030023Person-centred cultures are increasingly recognised as essential to the delivery of compassionate, safe, and effective healthcare. While Lean Six Sigma (LSS) is widely adopted as a process improvement methodology, its application is often critiqued for lacking alignment with relational or values-based care. This study aimed to test the transferability of three previously developed Programme Theories (PTs), generated through realist inquiry in a public hospital setting, within a large private acute hospital. Realist-informed adjudication workshops were conducted with interdisciplinary staff who had completed university-accredited training in LSS. Structured workbooks, visual artefacts, and thematic synthesis were used to identify how context–mechanism–outcome configurations (CMOCs) held, shifted, or evolved in the new setting. All three PTs were confirmed, with six CMOCs refined, and eight new configurations generated. Key refinements included the role of strategic intent, informal improvement communities, and intrinsic motivation. These findings suggest that values-based mechanisms underpinning person-centred LSS are not confined to public systems and may be equally active in private settings. The study confirms the explanatory strength of the original PTs while contributing new insights into their adaptability. It offers practical guidance for healthcare leaders seeking to embed person-centred improvement approaches across diverse systems, regardless of sectoral funding or governance structures.23en© 2025 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).http://creativecommons.org/licenses/by/4.0/Lean Six SigmaPerson-centred CulturesRealist EvaluationProgramme TheoryHealthcare ImprovementPrivate and Public HospitalsArticle