Table 2. Methodological assessment by Newcastle-Ottawa scale.

Study	Selection	Comparability	Outcome	Total
Behrem	2	2	2	6
Beketic	2	2	2	6
Chen	1	2	3	6
Chuang	2	2	2	6
Dales	3	2	3	8
Dassoulas	3	1	3	7
El-Gohary	2	2	3	7
Erdem	4	1	3	8
Huang	3	1	2	6
Koyama	4	1	2	7
Kyzas	2	2	3	7
Li	3	2	3	8
Lin	2	2	3	7
Lovato	3	1	2	6
Marioni	3	1	2	6
Martinovic	3	2	2	7
Martone	3	2	3	8
Mineo	2	1	3	6
Miyata	2	2	3	7
Nikiteas	2	2	3	7
Randall	3	2	3	8
Rau	3	2	1	6
Saad	3	2	2	7
Sakurai	2	2	3	7
Saroufim	3	2	3	8
Taskiran	3	2	2	7
Vayrynen	3	2	4	9
Yoshitomi	2	2	3	7
Zhou	2	2	2	6
Zvrko	3	2	2	7

Number indicates a quality score assessed from published articles.