Volume and health outcomes: evidence from systematic reviews and from evaluation of Italian hospital data.

BACKGROUND Improving quality and effectiveness of healthcare is one of the priorities of health policies. Hospital or physician volume represents a measurable variable with an impact on effectiveness of healthcare. An Italian law calls for the definition of «qualitative, structural, technological, and quantitative standards of hospital care». There is a need for an evaluation of the available scientific evidence in order to identify qualitative, structural, technological, and quantitative standards of hospital care, including the volume of care above or below which the public and private hospitals may be accredited (or not) to provide specific healthcare interventions. OBJECTIVES To identify conditions/interventions for which an association between volume and outcome has been investigated. To identify conditions/interventions for which an association between volume and outcome has been proved. To analyze the distribution of Italian health providers by volume of activity. To measure the association between volume of care and outcomes of the health providers of the Italian National Health Service (NHS). METHODS Systematic review An overview of systematic reviews was performed searching PubMed, EMBASE, and The Cochrane Library up to November 2016. Studies were evaluated by 2 researchers independently; quality assessment was performed using the AMSTAR checklist. For each health condition and outcome, if available, total number of studies, participants, high volume cut-off values, and metanalysis have been reported. According to the considered outcomes, health topics were classified into 3 groups: positive association: a positive association was demonstrated in the majority of studies/participants and/or a pooled measure (metanalysis) with positive results was reported; lack of association: both studies and/or metanalysis showed no association; no sufficient evidence of association: both results of single studies and metanalysis do not allow to draw firm conclusions on the association between volume and outcome. Analysis of the distribution of Italian hospitals by volume of activity and the association between volume of activity and outcomes: the Italian National Outcome evaluation Programme 2016 The analyses were performed using the Hospital Information System and the National Tax Register (year 2015). For each condition, the number of hospitals by volume of activity was calculated. Hospitals with a volume lower than 3-5 cases/year were excluded. For conditions with more than 1,500 cases/year and frequency of outcome ≥1%, the association between volume of care and outcome was analyzed estimating risk-adjusted outcomes. RESULTS Bibliographic searches identified 80 reviews, evaluating 48 different clinical areas. The main outcome considered was intrahospital/30-day mortality. The other outcomes vary depending on the type of condition or intervention in study. The relationship between hospital volume and outcomes was considered in 47 out of 48 conditions: 34 conditions showed evidence of a positive association; • 14 conditions consider cancer surgery for bladder, breast, colon, rectum, colon rectum, oesophagus, kidney, liver, lung, ovaries, pancreas, prostate, stomach, head and neck; • 11 conditions consider cardiocerebrovascular area: nonruptured and ruptured abdominal aortic aneurysm, acute myocardial infarction, brain aneurysm, carotid endarterectomy, coronary angioplasty, coronary artery bypass, paediatric heart surgery, revascularization of lower limbs, stroke, subarachnoid haemorrhage; • 2 conditions consider orthopaedic area: knee arthroplasty, hip fracture; • 7 conditions consider other areas: AIDS, bariatric surgery, cholecystectomy, intensive care unit, neonatal intensive care unit, sepsis, and traumas; for 3 conditions, no association was demonstrated: hip arthroplasty, dialysis, and thyroidectomy. for the remaining 10 conditions, the available evidence does not allow to draw firm conclusions about the association between hospital volume and considered outcomes: surgery for testicular cancer and intracranial tumours, paediatric oncology, aortofemoral bypass, cardiac catheterization, appendectomy, colectomy, inguinal hernia, respiratory failure, and hysterectomy. The relationship between volume of clinician/surgeon and outcomes was assessed only through the literature re view; to date, it is not possible to analyze this association for Italian health provider hospitals, since information on the clinician/surgeon on the hospital discharge chart is missing. The literature found a positive association for 21 conditions: 9 consider surgery for cancer: bladder, breast, colon, colon rectum, pancreas, prostate, rectum, stomach, and head and neck; 5 consider the cardiocerebrovascular area: ruptured and nonruptured abdominal aortic aneurysm, carotid endarterectomy, paediatric heart surgery, and revascularization of the lower limbs; 2 consider the orthopaedic area: knee and hip arthroplasty; 5 consider other areas: AIDS, bariatric surgery, hysterectomy, intensive care unit, and thyroidectomy. The analysis of the distribution of Italian hospitals concerned the 34 conditions for which the systematic review has shown a positive volume-outcome association. For the following, it was possible to conduct the analysis of the association using national data: unruptured abdominal aortic aneurysm, coronary angioplasty, hip arthroplasty, knee arthroplasty, coronary artery bypass, cancer surgery (colon, liver, breast, pancreas, lung, prostate, kidney, and stomach), laparoscopic cholecystectomy, hip fracture, stroke, acute myocardial infarction. For these conditions, the association between volume and outcome of care was observed. For laparoscopic cholecystectomy and surgery of the breast and stomach cancer, the association between the volume of the discharge (o dismissal) operating unit and the outcome was analyzed. The outcomes differ depending on the condition studied. The shape of the relationship is variable among different conditions, with heterogeneous slope of the curves. DISCUSSION For many conditions, the overview of systematic reviews has shown a strong evidence of association between higher volumes and better outcomes. The quality of the available reviews can be considered good for the consistency of the results between the studies and for the strength of the association; however, this does not mean that the included studies are of good quality. Analyzing national data, potential confounders, including age and comorbidities, have been considered. The systematic review of the literature does not permit to identify predefined volume thresholds. The analysis of national data shows a strong improvement in outcomes in the first part of the curve (from very low to higher volumes) for most conditions. In some cases, the improvement in outcomes remains gradual or constant with the increasing volume of care; in other, the analysis could allow the identification of threshold values beyond which the outcome does not further improve. However, a good knowledge of the relationship between effectiveness of treatments and costs, the geographical distribution and the accessibility to healthcare services are necessary to choose the minimum volumes of care, under which specific health procedures could not been provided in the NHS. Some potential biases due to the use of information systems data should also be considered. The different way of coding among hospitals could lead to a different selection of cases for some conditions. Regarding the definition of the exposure (volume of care), a possible bias could result from misclassification of health providers with high volume of activity. Performing the intervention in different departments/ units of the same hospital would result in an overestimation of the volume of care measured for hospital rather than for department/unit. For the conditions with a further fragmentation within the same structure, the association between volumes of discharge department and outcomes has also been evaluated. In this case, the two curves were different. The limit is to attribute the outcome to the discharge unit, which in case of surgery may not be the intervention unit. A similar bias could occur if the main determinant of the outcome of treatment was the caseload of each surgeon. The results of the analysis may be biased when different operators in the same hospital/unit carried out the same procedure. In any case, the observed association between volumes and outcome is very strong, and it is unlikely to be attributable to biases of the study design. Another aspect on which there is still little evidence is the interaction between volume of the hospital and of the surgeon. A MEDICARE study suggests that in some conditions, especially for specialized surgery, the effect of the surgeon's volume of activity is different depending on the structure volume, whereas it would not differ for some less specialized surgery conditions. The data here presented still show extremely fragmented volumes of both clinical and surgical areas, with a predominance of very low volume structures. Health systems operate, by definition, in a context of limited resources, especially when the amount of resources to allocate to the health system is reduced. In such conditions, the rationalization of the organization of health services based on the volume of care may make resources available to improve the effectiveness of interventions. The identification and certification of services and providers with high volume of activity can help to reduce differences in the access to non-effective procedures. To produce additional evidence to guide the reorganization of the national healthcare system, it will be necessary to design further primary studies to evaluate the effectiveness and safety of policies aimed at concentrating interventions in structures with high volumes of activity.