SNS Research Brief 62. The volume-outcome relationship in healthcare

Research has consistently found that hospitals with higher patient volumes have better patient outcomes than smaller hospitals, more or less regardless of the type of disease or treatment. The mechanism behind this association has often been explained from the perspective of “practice makes perfect.” In other words, healthcare professionals and provider organizations learn from experience, which in turn may enhance patient outcomes through, for example, a reduced risk of medical errors. Thus, low patient volumes in some areas of healthcare, such as surgical removal of cancer tumours, have prompted authorities in several countries, including the United Kingdom, the Netherlands, and Denmark, to undertake reorganizations of the healthcare system. Furthermore, in the United States, several professional organizations in the healthcare sector have advocated for establishing minimum volume standards for certain med-ical procedures as an indicator of high-quality care. However, it is crucial to distinguish be-tween patterns of correlation versus causation in this context. Whereas a correlation refers to an unspecified association between two variables, such as quality of care and patient volume, causation suggests a causal link from one variable to the other. Correlation does not imply causation per se. Therefore, it is crucial to understand the direction of the relationship before implementing any reforms.