Statistical analysis
The statistical analyses were performed using R version 2.14
[16-17]. The meta pack was used to calculate and generate the pooled
estimates and forest plots. Publication bias was also investigated
statistically using Egger and Begg tests [18-19]. Statistical
heterogeneity was assessed using the I2 test, with a
value ≥ 50% indicating a substantial level of heterogeneity. Random
effects models would be used when substantial statistical heterogeneity
was present. A p-value ≤ 0.05 was defined as statistically significant.