All items are scored 0 (not reported), 1 (reported but inadequate) and 2 (reported and adequate). The maximum score for non-comparative studies is 16 and the maximum score for comparative studies is 24. 1, a clearly stated aim; 2, inclusion of consecutive patients; 3, prospective collection of data; 4, endpoints appropriate to the aim of the study; 5, unbiased assessment of the study endpoint; 6, follow-up period appropriate to the aim of the study; 7, loss to follow-up less than 5%; 8, prospective calculation of the study size; 9, an adequate control group; 10, contemporary groups; 11, baseline equivalence of groups; 12, adequate statistical analyses.

NA, not applicable.