Table 3. Assessment of Methodological Quality of Included Observational Cohort Studies^a.

Studies Included	Selection				Comparability		Outcome			Scores
	1	2	3	4	5	6	7	8	9
Fang Li 2008 (21)	√	√	√	√	√	√	√	√	√	9
Liya Huo 2008 (10)	√	√	√	√	√	√	√	√	√	9
Qiheng Xu 2009 (22)	√	√	√	√			√	√	√	7
Cuijun Peng 2010 (23)	√	√	√	√	√	√	√	√	√	9
Yaoli Cui 2010 (24)	√	√	√	√	√	√	√	√	√	9
Hongbo Gao 2011 (25)	√	√	√	√			√	√		6
Tianyan Chen 2012 (26)	√	√	√	√	√	√	√	√	√	9
Jing Lai 2013 (12)		√	√	√	√	√	√	√	√	8
Junshuai Wang 2014 (27)	√	√	√	√	√	√	√	√	√	9

^a For cohort studies, 1 indicates exposed cohort truly representative; 2, non-exposed cohort drawn from the same community; 3, ascertainment of exposure; 4, outcome of interest not present at start; 5, cohorts comparable based on TBIL and PTA; 6, cohorts comparable on other factors; 7, quality of outcome assessment; 8, follow-up long enough for outcomes to occur; and 9, adequacy of follow-up of cohorts