Endoscopy vs surgery in the treatment of early gastric cancer: Systematic review

Table 2 Quality measures of the analyzed studies: Newcastle-Ottawa Scale - Bias measures

Ref.	Representativeness of exposed cohort and selection of the non exposed cohort (max. 2 points)	Ascertainment of exposure (max. 1 point)	Demonstration that outcome of interest was not present at start of study (max. 1 point)	Comparability of cohorts on the basis of the design or analysis (max. 2 points)	Assessment of outcome (max. 1 point)	Length and adequacy of follow up (max. 2 points)	Score and levels of evidence
Nishida et al[16]	2	1	1	1	1	1	7 - 2b - acceptable (+)
Fukase et al[14]	2	1	1	1	1	1	7 - 2b - acceptable (+)
Kim et al[17]	2	1	1	2	1	2	9 - 2b - acceptable (+)
Etoh et al[15]	2	1	1	2	1	2	9 - 2b - acceptable (+)
Choi et al[18]	2	1	1	2	1	2	9 - 2b - acceptable (+)
Chiu et al[19]	2	1	1	1	1	2	8 - 2b - acceptable (+)
Fukunaga et al[20]	2	1	1	1	1	2	8 - 2b - acceptable (+)
Park et al[21]	2	1	1	2	1	2	9 - 2b - acceptable (+)
Kim et al[22]	2	1	1	2	1	2	9 - 2b - acceptable (+)
Choi et al[23]	2	1	1	2	1	2	9 - 2b - acceptable (+)
Kim et al[24]	2	1	1	2	1	2	9 - 2b - acceptable (+)