BMJ 2000;320:1208 ( 29 April )

Letters

Will eradication of Helicobacter pylori improve symptoms of non-ulcer dyspepsia?

    Studies included in meta-analysis had heterogenous, not homogenous, results
    This meta-analysis is potentially misleading
    Meta-analysis included unreliable studies
    More studies should have been included in meta-analysis
    Authors' reply

Studies included in meta-analysis had heterogenous, not homogenous, results

The first 150 words of the full text of this article appear below.

EDITOR---Jaakkimainen et al's meta-analysis concludes that an improvement in dyspeptic symptoms occurred among patients with non-ulcer dyspepsia in whom Helicobacter pylori was eradicated.1 Unfortunately, there is a small but crucial problem at the heart of the analysis. The authors report that the summary estimates are statistically homogenous, but this is incorrect. In the observational studies the P value of <0.001 indicates massive heterogeneity between the results of the studies included. In the therapeutic trials the P value of 0.046 also indicates heterogeneity.

Meta-analysts faced with such heterogeneity have three choices: they may ignore the heterogeneity and pool the results with a fixed effects model; they may use a random effects model, which takes the heterogeneity into account; or they may decide not to pool the results. In this instance the authors chose to use a fixed effects model despite the heterogeneity. In consequence the confidence intervals of the pooled . . . [Full text of this article]
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