Article type
Year
Abstract
Background: although most Chinese-sponsored drug-related randomized controlled trials (CS-D-RCTs) are published in Chinese, researchers always fail to search Chinese bibliographic databases when conducting systematic reviews.
Objectives: our study aimed to evaluate language bias and location bias among CS-D-RCTs. We hypothesized:
1) CS-D-RCTs with positive results are more likely to be published in English journals than the ones with negative results;
2) CS-D-RCTs with positive results are more likely to be indexed in English bibliographic databases than the ones with negative results.
Methods: we conducted a retrospective cohort study among CS-D-RCTs registered in the primary registries of the International Clinical Trials Registry Platform of the World Health Organization.
We defined an eligible CS-D-RCT as an RCT where:
1) one of the experimental interventions was drug or biological;
2) at least one sponsor was located in mainland China;
3) at least one recruitment center was located in mainland China; and
4) it was conducted between 1 January 2008 and 31 December 2014.
We mapped eligible records to journal articles indexed in three English bibliographic databases and four Chinese bibliographic databases. The searching terms were developed with librarians according to the Cochrane Handbook for Systematic Reviews of Interventions. The data collection process was conducted by two authors independently and adjudicated with a third author.
A CS-D-RCT was considered positive if the primary outcome statistically supported the study hypothesis. Logistic regression models were used to adjust for covariates.
Results: we identified 1003 eligible CS-D-RCTs registered in four primary registries: 621 from the Chinese Clinical Trial Registry, 324 from ClinicalTrials.gov, 52 from the ISRCTN registry, and six from the Australian New Zealand Clinical Trials Registry. Among the 548 (55%) CS-D-RCTs that were published by March 2019, 422 (77%) were published in English, while 126 (23%) were published in Chinese. The 422 English articles were all indexed in English bibliographic databases, while 30 (24%) of the 126 Chinese articles were indexed in English bibliographic databases.
Adjusting for covariates, the risk of being published in English among CS-D-RCTs with positive results was 4.9 times (95% CI 3.7 to 6.1) the risk among CS-D-RCTs with negative results, while the risk of being indexed in English bibliographic databases among CS-D-RCTs with positive results was 4.7 times (95% CI 3.4 to 6.0) the risk among CS-D-RCTs with negative results.
Conclusions: our study supports the existence of language bias and location bias among CS-D-RCTs registered in trial registries. Reviewers should search Chinese bibliographic databases to reduce the effect of language bias and location bias on systematic reviews.
No patient or healthcare consumer was directly involved in this study.
Objectives: our study aimed to evaluate language bias and location bias among CS-D-RCTs. We hypothesized:
1) CS-D-RCTs with positive results are more likely to be published in English journals than the ones with negative results;
2) CS-D-RCTs with positive results are more likely to be indexed in English bibliographic databases than the ones with negative results.
Methods: we conducted a retrospective cohort study among CS-D-RCTs registered in the primary registries of the International Clinical Trials Registry Platform of the World Health Organization.
We defined an eligible CS-D-RCT as an RCT where:
1) one of the experimental interventions was drug or biological;
2) at least one sponsor was located in mainland China;
3) at least one recruitment center was located in mainland China; and
4) it was conducted between 1 January 2008 and 31 December 2014.
We mapped eligible records to journal articles indexed in three English bibliographic databases and four Chinese bibliographic databases. The searching terms were developed with librarians according to the Cochrane Handbook for Systematic Reviews of Interventions. The data collection process was conducted by two authors independently and adjudicated with a third author.
A CS-D-RCT was considered positive if the primary outcome statistically supported the study hypothesis. Logistic regression models were used to adjust for covariates.
Results: we identified 1003 eligible CS-D-RCTs registered in four primary registries: 621 from the Chinese Clinical Trial Registry, 324 from ClinicalTrials.gov, 52 from the ISRCTN registry, and six from the Australian New Zealand Clinical Trials Registry. Among the 548 (55%) CS-D-RCTs that were published by March 2019, 422 (77%) were published in English, while 126 (23%) were published in Chinese. The 422 English articles were all indexed in English bibliographic databases, while 30 (24%) of the 126 Chinese articles were indexed in English bibliographic databases.
Adjusting for covariates, the risk of being published in English among CS-D-RCTs with positive results was 4.9 times (95% CI 3.7 to 6.1) the risk among CS-D-RCTs with negative results, while the risk of being indexed in English bibliographic databases among CS-D-RCTs with positive results was 4.7 times (95% CI 3.4 to 6.0) the risk among CS-D-RCTs with negative results.
Conclusions: our study supports the existence of language bias and location bias among CS-D-RCTs registered in trial registries. Reviewers should search Chinese bibliographic databases to reduce the effect of language bias and location bias on systematic reviews.
No patient or healthcare consumer was directly involved in this study.