Items 1–12 represent the following: (1) a clearly stated aim; (2) inclusion criteria for consecutive patients; (3) prospective collection of data; (4) endpoints appropriate for the aim of this study; (5) unbiased assessment of the study endpoint; (6) follow-up period appropriate to the aim of the study; (7) loss to follow-up of less than 5%; (8) prospective calculation of study size; (9) adequate control group; (10) contemporary group; (11) baseline equivalence of groups; and (12) appropriate statistical analyses. A score of 0 means not mentioned, 1 means reported but inadequate, and 2 means reported and adequate. The total score is 24 for studies with control groups and 16 for studies without control groups. Quality is considered low (0–9 for studies with control groups, 0–7 for studies without control groups), moderate (10–20 for studies with control groups, 8–13 for studies without control groups), or high (20–24 for studies with control groups, 14–16 for studies without control groups) based on the total score.

MINORS, methodological index for non-randomized studies.