Table 5.

Risk of bias assessment of retrospective studies

	Adequacy of case definition	Case number	Representativeness of the cases	As of interventions	As of detection method	As of cutoff	As of outcome	Adequacy of follow up	NOS score
Huang, 2019 [23]	Low risk	High risk	High risk	Low risk	Low risk	Low risk	Low risk	Low risk	7
Jin, 2014 [21]	Low risk	High risk	High risk	Low risk	High risk	Low risk	Unclear risk	Low risk	5
Liu, 2016 [20]	Unclear risk	High risk	Low risk	Low risk	Low risk	Unclear risk	High risk	High risk	5
Liu, 2016 [18]	Low risk	Low risk	High risk	Low risk	Low risk	Low risk	Low risk	Low risk	8
Sun, 2016 [19]	Low risk	Low risk	Low risk	Low risk	Low risk	Low risk	Low risk	Low risk	8
Wang, 2018 [16]	Low risk	High risk	Low risk	Low risk	Low risk	Low risk	Low risk	Low risk	8
Wang, 2017 [13]	Low risk	High risk	Low risk	Unclear risk	Low risk	Low risk	Low risk	Low risk	7
Wang, 2019 [12]	Low risk	High risk	Low risk	Low risk	Low risk	Low risk	Low risk	Low risk	8
Wang, 2019 [11]	Low risk	Low risk	Unclear risk	Low risk	Unclear risk	Low risk	Low risk	Low risk	7
Xiao, 2019 [14]	Low risk	High risk	Low risk	High risk	Low risk	Unclear risk	High risk	Low risk	5
Ye, 2017 [17]	Unclear risk	Low risk	Low risk	Low risk	Low risk	Low risk	Low risk	Low risk	8
Qi, 2019 [22]	Low risk	Low risk	Low risk	Low risk	Low risk	Low risk	Low risk	Low risk	7

AS Ascertainment