PNPLA3 polymorphism increases risk for and severity of chronic hepatitis C liver disease

Table 2 Newcastle - Ottawa Scale on quality score of the included studies

Ref.	Selection				Comparability	Exposure			Total
	Independent validation	Case representation	Controls selection	Controls definition	Case and control design/analysis	Ascertainment of exposure	Same method of ascertainment	Same response rate
Cai et al[39] (2011)	1	1			2	1	1	1	7
Valenti et al[40] (2011)	1	1	1	1	2	1	1	1	9
Trépo et al[41] (2011)	1	1			2	1			5
Corradini et al[42] (2011)	1	1			2	1			5
Nischalke et al[13] (2011)	1	1	1	1	2	1	1	1	9
Valenti et al[43] (2012)	1	1			2	1	1		6
Valenti et al[15] (2012)	1	1			2	1	1		6
Guyot et al[12] (2013)	1	1			2	1			5
Ezzikouri et al[44] (2013)	1	1	1	1	2	1	1	1	9
Stättermayer et al[45] (2014)	1	1			2	1			5
Ampuero et al[46] (2014)	1	1			2	1	1	1	7
Sato et al[47] (2014)	1	1			2	1			5
Yasui et al[48] (2014)	1	1			2	1			5
Petta et al[14] (2015)	1	1			2	1			5
Nakaoka et al[49] (2015 )	1	1			2	1			5
Tamaki et al[50] (2015)	1	1			2	1	1	1	7
Huang et al[51] (2015)	1	1			2	1	1	1	7
Petta et al[52] (2016)	1	1			2	1	1	1	7
Ali et al[53] (2016)	1	1			2	1	1	1	7