Examples of 2 hypothetical meta-analyses with high statistical heterogeneity but with differing interpretations of overall direction of effect estimates.

(a) High statistical heterogeneity with inconsistency in direction of effects (uncertain benefit or harm). (b) High statistical heterogeneity with consistency in direction of effects (benefit). Blue boxes represent effect estimates from individual studies; red diamonds represent pooled effect estimates. Risk ratio greater than 1 represents benefit, less than 1 represents harm [37–40].