The effect of minimum volume standards in hospitals (MIVOS) — protocol of a systematic review

BACKGROUND: The volume-outcome relationship, i.e., higher hospital volume results in better health outcomes, has been established for different surgical procedures as well as for certain nonsurgical medical interventions. Accordingly, many countries such as Germany, the USA, Canada, the UK, and Switzerland have established minimum volume standards. To date, there is a lack of systematically summarized evidence regarding the effects of such regulations. METHODS: To be included in the review, studies must measure any effects connected to minimum volume standards. Outcomes of interest include the following: (1) patient-related outcomes, (2) process-related outcomes, and (3) health system-related outcomes. We will include (cluster) randomized controlled trials ([C]RCTs), non-randomized controlled trials (nRCTs), controlled before-after studies (CBAs), and interrupted time-series studies (ITSs). We will apply no restrictions regarding language, publication date, and publication status. We will search MEDLINE (via PubMed), Embase (via Embase), CENTRAL (via Cochrane Library), CINHAL (via EBSCO), EconLit (via EBSCO), PDQ evidence for informed health policymaking, health systems evidence, OpenGrey, and also trial registries for relevant studies. We will further search manually for additional studies by cross-checking the reference lists of all included primary studies as well as cross-checking the reference lists of relevant systematic reviews. To evaluate the risk of bias, we will use the ROBINS-I and RoB 2 risk-of-bias tools for the corresponding study designs. For data synthesis and statistical analyses, we will follow the guidance published by the EPOC Cochrane group (Cochrane Effective Practice and Organisation of Care (EPOC), EPOC Resources for review authors, 2019). DISCUSSION: This systematic review focuses on minimum volume standards and the outcomes used to measure their effects. It is designed to provide thorough and encompassing evidence-based information on this topic. Thus, it will inform decision-makers and policymakers with respect to the effects of minimum volume standards and inform further studies in regard to research gaps. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42022318883 SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13643-022-02160-7.