The pooled analysis was conducted using the RevMan 5.1 software if a polymorphism was reported by two or more studies.



RevMan
A comprehensive literature search from PubMed, Web of Science, and Chinese National Knowledge Infrastructure was conducted for all potentially relevant studies published before January 2, 2017. 
PubMed
A comprehensive literature search from PubMed, Web of Science, and Chinese National Knowledge Infrastructure was conducted for all potentially relevant studies published before January 2, 2017. 
Web of Science
A comprehensive literature search from PubMed, Web of Science, and Chinese National Knowledge Infrastructure was conducted for all potentially relevant studies published before January 2, 2017. 
Chinese National Knowledge Infrastructure