EDITOR,--In their response1 to our editorial on misleading meta-analysis2 A Perry and R Persaud state that we ignored the degree of heterogeneity among different studies. We examined the case of intravenous magnesium in acute myocardial infarction, a treatment recently shown to be of no benefit in a trial.3 We argued that the asymmetrical funnel plot (a plot of the estimates of effect sizes against the sample size) should have alerted meta-analysts to the possible presence of bias. The erroneous conclusion …