Funnel plots are thought to detect publication bias.
Heterogeneity is thought to detect fundamental differences between studies.
New evidence suggests that both of these common beliefs are badly flawed. Bandolier generally eschews heavy stuff on complex methodological issues in systematic reviews and meta-analysis. The reasons involve their complexity, and the fact that mostly the details interest only the anoraks among us. The trouble is that some folks seem to think that these methodological topics are cast in stone, and that any meta-analysis that had an asymmetric funnel plot or demonstrates statistical heterogeneity is so badly flawed that the treatment it reviews must be dismissed. What's worse is that these are often reasons used to advise against prescribing treatments that are effective.