Consumption of coffee associated with reduced risk of liver cancer: a meta-analysis

BMC Gastroenterology

Table 1 Quality assessment of case–control studies included in this meta-analysis ¹

Study	Adequate definition of cases	Representativeness of cases	Selection of control	Definition of control	Control for important factor or additional factor²	Exposure assessment	Same method of ascertainment for cases and controls	Nonresponse rate³	Total quality scores
Kuper et al. [11], 2000	★	★	-	★	★	-	★	-	5
Gallus et al. [12], 2002	★	★	-	★	★	-	★	-	6
Gelatti et al. [13], 2005	★	★	-	★	★★	★	★	-	7
Ohfuji et al. [14], 2006	★	★	-	★	★★	-	★	-	6
Tanaka et al. [15], 2007	★	★	★	★	★	-	★	-	6
Montella et al. [16], 2007	★	★	-	★	★★	-	★	-	6
Wakai et al. [17], 2007	★	★	★	★	★	-	★	-	6
Ohish et al. [18], 2008	★	★	★	★	★★	-	★	-	7
Leung et al. [19], 2011	★	★	-	★	-	★	★	-	5

¹A study can be awarded a maximum of one star for each numbered item except for the item Control for most important factor or second important factor.
² A maximum of two stars can be awarded for Control for most important factor or second important factor. Studies that controlled for hepatitis B virus (HBV) or HCV infection received one star, whereas studies that controlled for alcohol drinking received one additional star.
³ One star was awarded if there was no significant difference in the response rate between control subjects and cases in the chi-square test (P > 0.05).

ISSN: 1471-230X