Eligible studies were collected from nine databases (ie, PubMed, Medline, Embase, Cochrane Library, Ovid, Science Citation Index Expanded, China Biology Medicine, Chinese National Knowledge Infrastructure, and Wanfang). 
PubMed
Eligible studies were collected from nine databases (ie, PubMed, Medline, Embase, Cochrane Library, Ovid, Science Citation Index Expanded, China Biology Medicine, Chinese National Knowledge Infrastructure, and Wanfang). 
Medline
Eligible studies were collected from nine databases (ie, PubMed, Medline, Embase, Cochrane Library, Ovid, Science Citation Index Expanded, China Biology Medicine, Chinese National Knowledge Infrastructure, and Wanfang). 
Embase
Eligible studies were collected from nine databases (ie, PubMed, Medline, Embase, Cochrane Library, Ovid, Science Citation Index Expanded, China Biology Medicine, Chinese National Knowledge Infrastructure, and Wanfang). 
Cochrane Library
Eligible studies were collected from nine databases (ie, PubMed, Medline, Embase, Cochrane Library, Ovid, Science Citation Index Expanded, China Biology Medicine, Chinese National Knowledge Infrastructure, and Wanfang).  The analysis provided evidence suggesting a significant negative correlation between high CRNDE expression and the rate of overall survival [HR=1.92, 95% CI (1.40-2.64), p<0.001] in patients with malignancies of the digestive system. 
Ovid
Eligible studies were collected from nine databases (ie, PubMed, Medline, Embase, Cochrane Library, Ovid, Science Citation Index Expanded, China Biology Medicine, Chinese National Knowledge Infrastructure, and Wanfang). 
Science Citation Index Expanded
Eligible studies were collected from nine databases (ie, PubMed, Medline, Embase, Cochrane Library, Ovid, Science Citation Index Expanded, China Biology Medicine, Chinese National Knowledge Infrastructure, and Wanfang). 
China Biology Medicine
Eligible studies were collected from nine databases (ie, PubMed, Medline, Embase, Cochrane Library, Ovid, Science Citation Index Expanded, China Biology Medicine, Chinese National Knowledge Infrastructure, and Wanfang). 
Chinese National Knowledge Infrastructure
Eligible studies were collected from nine databases (ie, PubMed, Medline, Embase, Cochrane Library, Ovid, Science Citation Index Expanded, China Biology Medicine, Chinese National Knowledge Infrastructure, and Wanfang). 
Wanfang