Figure 4.

Funnel plots for studies included in the meta-analysis (a). Visual inspection suggested that publication could be ruled out, as otherwise confirmed by the results of Egger test (t = −0.01, df = 9, p-value = 0.990). (b) Similarly, in radial plots (b), the estimates for included studies were substantially scattered across the regression line, suggesting the ruling out of a potential small study effect.