[Relationship between hospital volumes and health outcomes: epidemiological evidence supporting the revision process of the Ministry of Health Decree no. 70 of 2 April 2015.]

Since its enactment on 2 April 2015, the Decree of the Ministry of Health no.70 has provided a key framework for the reorganization of services to enhance the quality and safety of care. This decree presents the volume thresholds for a series of nosological areas and diagnostic-therapeutic procedures, aiming to improve healthcare outcomes. These thresholds are expected to be periodically updated based on the most recent scientific developments. In this perspective, this work intends to establish whether statistical correlations exist between volumes of activity and outcomes of hospital care. The scope is limited to several clinical conditions and therapeutic procedures for which specific indicators are provided by the National Healthcare Outcomes Programme (Programma Nazionale Esiti - PNE). For each condition or procedure, the analysis shows the volume-outcome relationship by hospital centre by means of the Levenberg-Marquardt algorithm (software: XLSTAT). The existence of breakpoints is assessed through the use of segmented models (software: "segmented" R-Package). The results show a statistical correlation for the following: acute myocardial infarction (breakpoint: 91 hospitalizations per year; 95% CI: 81-101; p<0.0001); repair of an unruptured abdominal aortic aneurysm (breakpoint: 69 procedures per year; 95% CI: 52-86; p=0.146); lung cancer (breakpoint: 96 procedures per year; 95% CI: 60-132; p<0.01); knee arthroplasty (breakpoint: 91 procedures per year; 95% CI: 51-131; p=0.484). Conversely, the statistical analysis did not allow to accurately highlight a breakpoint for the isolated aorto-coronary bypass, percutaneous transluminal coronary angioplasty and hip arthroplasty. These results represent a useful knowledge contribution to support the revision process of the above-mentioned Decree. As regards the procedures that may not be currently assessed through this statistical analysis method, literature data is referred to that confirm that the current regulatory thresholds are in the safe range.