How to read a forest plot in a meta-analysis:

Researchers undertook a meta-analysis of the effect of treating Helicobacter pylori with eradication therapy on the subsequent occurrence of gastric cancer. Randomised controlled trials were included if the intervention consisted of seven days or more of eradication therapy, and if the control treatment was placebo or no treatment. Participants were adults who tested positive for H pylori . They were otherwise healthy and asymptomatic at baseline and were followed for two or more years. The primary outcome was the diagnosis of gastric cancer.1 Six randomised controlled trials were eligible for inclusion. The results of the meta-analysis comparing the intervention with control treatment in the occurrence of gastric cancer were presented in a forest plot (figure⇓). Fifty one (1.6%) gastric cancers occurred in 3294 participants who received eradication therapy compared with 76 (2.4%) in 3203 control subjects (relative risk 0.66, 95% confidence interval 0.46 to 0.95). Forest plot of randomised controlled trials of Helicobacter pylori eradication therapy: effect on subsequent occurrence of gastric cancer Which of the following statements, if any, are true? Statements b and d are true, whereas a , c, and e are false. The aim of the meta-analysis was to combine the results of trials that investigated the effectiveness …