Relationship between Helicobacter pylori infection and programmed death-ligand 1 in gastric cancer: A meta-analysis

Table 2 The Newcastle-Ottawa scores of the included studies

Ref.	Adequate definition of cases	Representativeness of cases	Selection of controls	Definition of controls	Control for age and sex	Control for other confounders	Exposure ascertainment	Same methods for events ascertainment	Non-response rates	Total
Koizumi et al[27], 2022	1	1	1	1	0	0	1	1	1	7
Shen et al[28], 2019	1	1	1	1	0	0	1	1	1	7
Yoshida et al[29], 2022	1	1	1	1	0	0	1	1	0	6
Böger et al[30], 2016	1	1	1	1	0	0	1	1	1	7
Che et al[18], 2022	1	1	1	1	0	0	1	1	0	6
Magahis et al[31], 2023	1	1	1	1	0	0	1	1	0	6
Wu et al[32], 2017	1	1	1	1	0	0	1	1	0	6
Jia et al[17], 2024	1	1	1	1	0	0	1	1	1	7
Liu et al[33], 2020	1	1	1	1	0	0	1	1	0	6
Di Bartolomeo et al[34], 2015	1	1	1	1	0	0	1	1	1	7
Kuo et al[35], 2017	1	1	1	1	0	0	1	1	1	7
Sughayer et al[36], 2020	1	1	1	1	0	0	1	1	1	7
Tseng et al[37], 2020	1	1	1	1	0	0	1	1	1	7
Fang et al[38], 2020	1	1	1	1	0	0	1	1	1	7