Table 1

Assessment of bias among included studies—MINORS’ criteria.

Items	Peng et al, 200910	Jiang et al, 201111	Abdelaal et al, 202012	Nakamura et al, 201913	Zhou et al, 201714	Zheng et al, 202215	Zheng et al, 202216	Zhong et al, 201617
A clearly stated aim	2	2	2	2	2	2	2	2
Inclusion of consecutive patients	2	2	2	2	2	2	2	2
Prospective collection of data	2	2	2	2	2	2	2	2
Endpoints appropriate to the aim of the study	2	2	2	2	2	2	2	2
Unbiased assessment of the study endpoint	2	1	2	2	2	2	2	2
Follow-up period appropriate to the aim of the study	2	1	2	2	2	2	2	2
Loss of follow-up less than 5%	2	2	2	2	2	2	2	2
Prospective calculation of study size	0	0	0	0	0	0	0	0
An adequate control group	0	0	0	0	0	2	0	0
Contemporary groups	0	0	0	0	0	0	0	0
Baseline equivalence of groups	0	0	0	0	0	0	0	0
Adequate statistical analysis	1	1	1	1	1	2	2	1
Total	15	13	15	15	13	18	16	15
Risk	Low	Low	Low	Low	Low	Low	Low	Low

Abbreviation: MINORS, methodological index for non-randomized studies.
Note: 2 (green) is considered good, 1 (yellow) is considered moderate, and 0 (red) is no score.