Table 2. Quality assessment for non-randomized trials.

Quality assessment for non-randomized trials	Acar et al.[14]	Klauser[11]	Wendelstein et al.[16]
A clearly stated aim	2	2	2
Inclusion of consecutive patients	1	2	2
Prospective data collection	0	0	0
Endpoints appropriate to the aim of the study	2	2	2
Unbiased assessment of the study endpoint	2	2	2
A follow-up period appropriate to the aims of study	2	2	2
Less than 5% loss to follow-up	0	2	2
Prospective calculation of the sample size	0	0	0
An adequate control group	2	2	2
Contemporary groups	2	2	2
Baseline equivalence of groups	2	2	2
Adequate statistical analyses	2	2	2
Total score	17	20	20