The grey literature search: a comparative analysis of meta analysis of interventions published in Chinese academic journals and Cochrane Library

Tags: Poster
Chen YL1, Yuan B1, Sun LN1, Li X1, Yang SF1, Sun R1, Yao L1, Li J1, Wang Q1, Zhang PZ1, Yang KH1
1Evidence-Based Medicine Center of Lanzhou University, China

Background: Grey literature must coincide with published material when conducting research, particularly systematic reviews. Reviewers will learn more when they search for grey literature.

Objectives: To investigate the Grey Literature search of systematic reviews between Chinese academic journals and Cochrane library.

Methods: We searched Chinese Biomedical Literature database (CBM) which is considered Chinese MEDLINE from January 2009 to December 2011 and all meta-analysis of interventions were included. We also searched Cochrane Database of Systematic Reviews (Issued 1, 2012) and 10% random samples of meta-analysis of interventions were included from 2009 to 2011. Each meta-analysis was independently identified and evaluated by two reviewers.

Results: We included 967 Chinese meta-analysises (CM) and 137 Cochrane meta-analysises (EM). Only 38 (6%) of CM reported they searched grey literature database, compared with 91 (66%) of EM. Twelve (1%) of CM reported they finally included grey references, compared with nine (7%) of EM. Three hundred and sixty seven (38%) of CM reported they searched other unpublished studies by Google and personal communications, compared with 89 (65%) of EM. 329 (34%) of CM reported they checked reference lists, compared with 119 (87%) of EM.

Conclusions: The systematic review should include any relevant type studies whether they were published or not. The Cochrane Handbook recommends search grey literatures. The rate of grey literatures searching of CM was very low compared with EM (1/10). Compared to EM, the rate of reference lists checking of CM was only half. Chinese systematic reviewers must comprehensive literature search if they wish to conduct high quality systematic reviews.