To the Editor: Most textbooks and guidance documents on systematic reviews discuss the caveats and potential risks of heterogeneity in meta-analysis. It is not appreciated that extreme homogeneity in a meta-analysis can be a far stronger signal of major problems. The careful meta-analysis of hydroxyethyl starch for fluid resuscitation by Dr Zarych-anski and colleagues exemplifies this issue. The Cochrane review on this topic showed extreme be-tween-study homogeneity (left-sided P=.001). When my team screened the entire Cochrane database to identify metaanalyses in which the results across the included studies were too homogeneous, that meta-analysis stood out and we communicated with the principal investigator (Dr Boldt) to find out how he had found such identical results across 5 seemingly different randomized trials. The author indicated that these were not overlapping data sets but that they did represent independent trials performed at different periods at the same institution.
展开▼
