Methodological quality assessment of network meta-analysis of drug interventions: implications from a systematic review

Background: We aimed to determine the methodological quality of network meta-analyses (NMAs) and their compliance with reporting guidelines. Methods: A systematic review of NMAs comparing any pharmacological interventions was performed (searches in Medline and Scopus). The characteristics of NMAs were collected by two independent reviewers. We applied R-AMSTAR to all NMAs, generating a methodological quality score that could range from 11 to 44 points. PRISMA and PRISMA-NMA reporting checklists were converted into quantitative scores (maximum values of 27 and 32 points). To normalize the values between these two checklists, a third score (PRISMA-SCORE) of 0-1 was created. The correlation of the scores with NMA publication year, journal impact factor and most productive countries were calculated using non-parametric tests. Results: We identified 477 NMAs. Only 36.1% of studies reported having followed PRISMA statements. The medians of R-AMSTAR, PRISMA and PRISMA-NMA scores were 28 (IQR 25-31), 21 (IQR 19-23) and 23 (IQR 19-26), respectively. Several problems were noted in NMAs (e.g. lack of study protocol, issues in literature searches, lack of raw data). NMAs from the most productive countries (USA and China) have similar methodological quality. Correlation analyses between R-AMSTAR and normalized PRISMA-SCORE revealed a strong positive correlation (Spearman's rho = 0.776; P<0.001). A weak but positive correlation was found for PRISMA-SCORE and journal impact factor (0.193; P<0.001). Conclusions: The important growth of NMA publication rate during the past 5 years is not associated with better methodological and reporting quality. Editors, peer reviewers, researchers and funding agencies should ensure that methodological and reporting standards are met before publication.