Is Volume Related to Outcome in Health Care? A Systematic Review and Methodologic Critique of the Literature

PURPOSE: To systematically review the methodologic rigor of the research on volume and outcomes and to summarize the magnitude and significance of the association between them. DATA SOURCES: The authors searched MEDLINE from January 1980 to December 2000 for English-language, population-based studies examining the independent relationship between hospital or physician volume and clinical outcomes. Bibliographies were reviewed to identify other articles of interest, and experts were contacted about missing or unpublished studies. STUDY SELECTION: Of 272 studies reviewed, 135 met inclusion criteria and covered 27 procedures and clinical conditions. DATA EXTRACTION: Two investigators independently reviewed each…