Assessment of Publication Bias
The presence of publication bias was evaluated using the Begg’s funnel
plot (4), which is a measure of the proportion (in the X-axis) against
the standard error of the proportion (in the Y-axis). Each open circle
represents an individual study in the meta-analysis. The line in the
centre indicates the pooled proportion and the other two lines indicate
the 95% CI. The proportion estimates from smaller studies are expected
to be scattered above and below the summary estimate, producing a
triangular or funnel shape, if there is no publication bias.