Protocol for the development of a core outcome set for studies on centralisation of healthcare services

Introduction Centralisation defined as the reorganisation of healthcare services into fewer specialised units serving a higher volume of patients is a potential measure for healthcare reforms aiming at reducing costs while improving quality. Research on centralisation of healthcare services is thus essential to inform decision-makers. However, so far studies on centralisation report a variability of outcomes, often neglecting outcomes at the health system level. Therefore, this study aims at developing a core outcome set (COS) for studies on centralisation of hospital procedures, which is intended for use in observational as well as in experimental studies. Methods and analysis We propose a five-stage study design: (1) systematic review, (2) focus group, (3) interview studies, (4) online survey, (5) Delphi survey. The study will be conducted from March 2022 to November 2023. First, an initial list of outcomes will be identified through a systematic review on reported outcomes in studies on minimum volume regulations. We will search MEDLINE, EMBASE, CENTRAL, CINHAL, EconLIT, PDQ-Evidence for Informed Health Policymaking, Health Systems Evidence, Open Grey and also trial registries. This will be supplemented with relevant outcomes from published studies on centralisation of hospital procedures. Second, we will conduct a focus group with representatives of patient advocacy groups for which minimum volume regulations are currently in effect in Germany or are likely to come into effect to identify outcomes important to patients. Furthermore, two interview studies, one with representatives of the German medical societies and one with representatives of statutory health insurance funds, as well as an online survey with health services researchers will be conducted. In our analyses of the suggested outcomes, we will largely follow the categorisation scheme developed by the Cochrane EPOC group. Finally, a two-round online Delphi survey with all stakeholder groups using predefined score criteria for consensus will be employed to first prioritise outcomes and then agree on the final COS. Ethics and dissemination This study has been approved by the Research Ethics Committee at the Brandenburg Medical School Theodor Fontane (MHB). The final COS will be disseminated to all stakeholders involved and through peer-reviewed publications and conferences.