Table 3.

Inclusion and exclusion criteria form

Criteria	Review result
Inclusion
Surgical hospital volume-outcome relationship	❒ Yes ❒ No
Methodology used precisely described (how the outcome was assessed, how the hospital volume was analysed and how the statistical analysis was performed).	❒ Yes ❒ No
Exclusion
Surgeon volume-outcome relationship only	❒ Yes ❒ No
Hospital volume used only as a covariate	❒ Yes ❒ No
Publication in the form of systematic reviews, qualitative studies, editorials, letters to the editor, comments or narrative reports	❒ Yes ❒ No