Minimally invasive surgical treatment of intrahepatic cholangiocarcinoma: A systematic review

Table 1 Study characteristics and quality assessment

Ref.	Country	Type of study		LS	OS	NOS			Minors
						Selection	Comparability	Outcame/Exposure
Wu et al[28], 2020	China	RetS-SC	Case control study	18	25	***	*	***	17
Haber et al[27], 2020	Germany	RetS-SC	Case control study	27	31	***	*	**	16
Kang et al[26], 2020	Korea	RetS-SC	Propensity score matching	30	61	***	**	***	18
Kinoshita et al[24], 2020	Japan	RetS-SC	Case control study	15	21	***	**	***	18
Ratti et al[25], 2020	United Kingdom-Italy	RetS-TC	Propensity score matching	104	104	***	**	***	19
Martin et al[23], 2019	United States	RetS-DB	Database	312	1997	**	*	**	15
Zhu et al[22], 2019	China	RetS-SC	Propensity score matching	20	63	***	**	***	19
Wei et al[21], 2017	China	RetS-SC	Case control study	30	20	***	**	***	19
Lee et al[20], 2016	Korea	RetS-SC	Case control study	14	23	***	**	***	20

LS: Number of patients treated with laparoscopic surgery; OS: Number of patients treated with open surgery; NOS: Newcastle-Ottawa Scale for assessing the quality of nonrandomised studies.A study can be awarded a maximum of one star (*) for each numbered item within the selection and exposure categories. A maximum of two stars can be given for comparability. MINORS: Methodological index for non-randomized studies; RetS: Retrospective study; SC: Single center; TC: Two centres; DB: Data base.