Huang et al have performed a meta-analysis to determine the relationship between
cagA seropositivity (by serology and polymerase chain reaction) and the risk of gastric cancer. An extensive review of the literature identified no previous systematic overviews. The authors identified 16 studies involving 2284 cases and 2770 controls. The overall prevalence of Helicobacter pylori was 77.7% in cases and 63.1% in controls. Tests for cagA were positive in 62.8% of cases and 37.5% of controls. Thus, H pyloriand cagA seropositivity significantly increased the risk for gastric cancer, by 2.28 (95% CI 1.71 to 3.05) and 2.87 (95% CI 1.95 to 4.22), respectively. In patients with H pylori, those who were infected by a cagA-positive strain had a slightly higher risk of gastric cancer, with an odds ratio of 1.64 (95% CI 1.21 to 2.24). The authors also found that patients infected with H pyloriwith or without cagA seropositivity had an increased risk of noncardia gastric cancer, but not of cancer of the gastric cardia. They concluded that cagA-positive strains confer a greater risk of gastric cancer than does H pylori infection alone.