3.6 Quality assessment and publication bias
Almost all studies in this meta-analysis were not of the same quality;
the lowest STROBE score was 17, and the highest was 20 for the articles
with full-text (Table 1). Potential sources of bias were not clear in
most of the articles. Moreover, the eligibility criteria of selection of
participants were not clear in the most of the articles. Figure 3
illustrates the relative symmetry of funnel plots of publications. At
the same time, there was no evidence of publication bias by the
calculation of the Egger test for small-study effects (P=0.160).
4. DISCUSSION