Improving the quality of healthcare in Japan: a systematic review of procedural volume and outcome literature.

Though some policies have been implemented based on volume-outcome relationships in Japan, no studies systematically reviewed volume-outcome research conducted in Japan. Original data used in this study were obtained from MEDLINE searches using PubMed or from searches of the Ichushi database and complemented with manual searches. Two investigators reviewed and scored 13 articles, using a standard form to extract information regarding key study characteristics and results.