Article type
Year
Abstract
Background: Language bias and indexing bias may exist among Chinese-Sponsored Randomized Controlled Trials (CS-RCTs). Such bias may threaten the validity of systematic reviews.
Objectives: To evaluate the existence of language bias and indexing bias among CS-RCTs on drug interventions.
Methods: In this retrospective cohort study we retrieved eligible CS-RCTs from trial registries and searched bibliographic databases to determine their publication status. The search and analysis were conducted from March to August 2019.
Trial registries included the primary trial registries recognized by the World Health Organization (WHO) and the Drug Clinical Trial Registry Platform (DCTRP) sponsored by the China Food and Drug Administration (China FDA). Eligible CS-RCTs were on drug interventions and conducted between January 2008 and December 2014.
Exposure was defined as individual CS-RCTs with positive (versus negative) results. For assessing language bias, the main outcome was the language of the journal where CS-RCTs were published (English versus Chinese). For indexing bias, the main outcome was the language of bibliographic database where the CS-RCTs were indexed (English versus Chinese).
Results: We identified 891 eligible CS-RCTs. Four hundred and seventy CS-RCTs were published by August 2019, of which 368 (78.3%) were published in English. Among CS-RCTs registered in the Chinese Clinical Trial Registry (ChiCTR), positive CS-RCTs were 3.92 (95%CI: 2.20-7.00) times more likely to be published in English than negative CS-RCTs; among CS-RCTs registered in English registries, positive CS-RCTs were 3.22 (95%CI: 1.34-7.78) times more likely to be published in English than negative CS-RCTs. These findings suggest the existence of language bias. Among CS-RCTs registered in ChiCTR, positive CS-RCTs were 2.89 (95%CI: 1.55-5.40) times more likely to be indexed in EBDs than negative CS-RCTs; among CS-RCTs registered in English registries, positive CS-RCTs were 2.19 (95%CI: 0.82-5.82) times more likely to be indexed in EBDs than negative CS-RCTs. These findings support the existence of indexing bias.
Conclusions: Our study indicates the existence of language bias and indexing bias among registered CS-RCTs on drug interventions. This may distort evidence-synthesis towards more positive results of drug interventions.
Patient or healthcare consumer involvement: None.
Objectives: To evaluate the existence of language bias and indexing bias among CS-RCTs on drug interventions.
Methods: In this retrospective cohort study we retrieved eligible CS-RCTs from trial registries and searched bibliographic databases to determine their publication status. The search and analysis were conducted from March to August 2019.
Trial registries included the primary trial registries recognized by the World Health Organization (WHO) and the Drug Clinical Trial Registry Platform (DCTRP) sponsored by the China Food and Drug Administration (China FDA). Eligible CS-RCTs were on drug interventions and conducted between January 2008 and December 2014.
Exposure was defined as individual CS-RCTs with positive (versus negative) results. For assessing language bias, the main outcome was the language of the journal where CS-RCTs were published (English versus Chinese). For indexing bias, the main outcome was the language of bibliographic database where the CS-RCTs were indexed (English versus Chinese).
Results: We identified 891 eligible CS-RCTs. Four hundred and seventy CS-RCTs were published by August 2019, of which 368 (78.3%) were published in English. Among CS-RCTs registered in the Chinese Clinical Trial Registry (ChiCTR), positive CS-RCTs were 3.92 (95%CI: 2.20-7.00) times more likely to be published in English than negative CS-RCTs; among CS-RCTs registered in English registries, positive CS-RCTs were 3.22 (95%CI: 1.34-7.78) times more likely to be published in English than negative CS-RCTs. These findings suggest the existence of language bias. Among CS-RCTs registered in ChiCTR, positive CS-RCTs were 2.89 (95%CI: 1.55-5.40) times more likely to be indexed in EBDs than negative CS-RCTs; among CS-RCTs registered in English registries, positive CS-RCTs were 2.19 (95%CI: 0.82-5.82) times more likely to be indexed in EBDs than negative CS-RCTs. These findings support the existence of indexing bias.
Conclusions: Our study indicates the existence of language bias and indexing bias among registered CS-RCTs on drug interventions. This may distort evidence-synthesis towards more positive results of drug interventions.
Patient or healthcare consumer involvement: None.