3.1 Eligible studies
The flowchart of the detailed search progress is illustrated in Figure 1. After removing the duplicated articles and browsing the abstracts, titles or full texts, consequently, seventeen studies15-31 with 4934 patients were enrolled in this meta-analysis. Among these studies, ten15,17-20,22,23,26-28 were retrospective cohort studies and seven 16,21,24,25,29-31 were prospective studies in which only one study 29 was a randomized controlled trial (RCT).