Impact of chronic proliferative cholangitis on stone recurrence and biliary strictures after intrahepatic stone treatment: A meta-analysis

Table 5 Newcastle-Ottawa Scale quality assessment of included observational studies

Ref.	Selection (Max 4)	Comparability (Max 2)	Outcome (Max 3)	Total NOS Score (Max 9)	Quality interpretation	Comments
Jin et al[12], 2016	4	1	2	7	Moderate quality	Retrospective surgical cohort; good case selection; limited adjustment for confounders
Tsutsumi et al[13], 2017	3	1	3	7	Moderate quality	Clear outcome assessment and follow-up; limited comparability between treatment approaches
Ishihara et al[14], 2021	3	2	3	8	High quality	Adequate follow-up; multivariable analysis used to assess recurrence risk
Torres et al[15], 2021	4	1	2	7	Moderate quality	Multicenter cohort; good selection; limited control for confounding
Yan et al[16], 2024	3	1	2	6	Moderate quality	Small sample size; high-risk population; outcome reporting adequate
Hakuta et al[17], 2024	4	2	3	9	High quality	Large cohort; clear outcome definitions; long-term follow-up and risk factor analysis

Max: Maximum score; NOS: Newcastle-Ottawa Scale.