The asymmetrical funnel plot indicates bias, including:

Selective reporting – The studies with negative result will be ingnored for reporting in a funnel plot.
True heterogeneity – Heterogenieity in study characteristics and methodology can lead to assymetry.
Publication bias – Some studies with small size and non-significant result would be remain unpublished, can cause gap in the funnel plot.

An asymmetrical funnel plot indicates that the meta-analysis may exaggerate the intervention effect.

Q & A Forum

Meta Analysis

Q: What does an asymmetrical funnel plot propose?

The asymmetrical funnel plot indicates bias, including:

Selective reporting – The studies with negative result will be ingnored for reporting in a funnel plot.
True heterogeneity – Heterogenieity in study characteristics and methodology can lead to assymetry.
Publication bias – Some studies with small size and non-significant result would be remain unpublished, can cause gap in the funnel plot.

An asymmetrical funnel plot indicates that the meta-analysis may exaggerate the intervention effect.

Cochrane Handbook for Systematic Reviews of Interventions. (2011). 10.4.1 Funnel plots. The Cochrane Collaboration. Retrieved from