Abstract
Systematic reviews and/or meta-analyses generally provide the best evidence for medical research. Authors are recommended to use flow diagrams to present the review process, allowing for better understanding among readers. However, no studies as of yet have assessed the quality of flow diagrams in systematic review/meta-analyses. Our study aims to evaluate the quality of systematic review/meta-analyses over a period of ten years, by assessing the quality of the flow diagrams, and the correlation to the methodological quality. Two hundred articles of “systematic review” and/or “meta-analysis” from January 2004 to August 2015 were randomly retrieved in Pubmed to be assessed for the flow diagram and methodological qualities. The flow diagrams were evaluated using a 16-grade scale corresponding to the four stages of PRISMA flow diagram. It composes four parts: Identification, Screening, Eligibility and Inclusion. Of the 200 articles screened, 154 articles were included and were assessed with AMSTAR checklist. Among them, 78 articles (50.6%) had the flow diagram. Over ten years, the proportion of papers with flow diagram available had been increasing significantly with regression coefficient beta = 5.649 (p = 0.002). However, the improvement in quality of the flow diagram increased slightly but not significantly (regression coefficient beta = 0.177, p = 0.133). Our analysis showed high variation in the proportion of articles that reported flow diagram components. The lowest proportions were 1% for reporting methods of duplicates removal in screening phase, followed by 6% for manual search in identification phase, 22% for number of studies for each specific/subgroup analysis, 27% for number of articles retrieved from each database, and 31% for number of studies included in qualitative analysis. The flow diagram quality was correlated with the methodological quality with the Pearson’s coefficient r = 0.32 (p = 0.0039). Therefore, this review suggests that the reporting quality of flow diagram is less satisfactory, hence not maximizing the potential benefit of the flow diagrams. A guideline with standardized flow diagram is recommended to improve the quality of systematic reviews, and to enable better reader comprehension of the review process.
Highlights
Systematic review is a form of literature review that assembles and analyzes several studies related to a specific question, with the aim of synthesizing the respective findings of the studies, basing on the methods framed at the beginning of the procedure [1,2,3,4]
Of all 78 available flow diagrams, the reporting of items in flow diagram was considerably different: 12% of flow diagrams missed the total number of articles identified, 62% of flow diagrams did not describe the name of databases or search engines used, 73% of flow diagrams ignored the number of papers from each database or search engine (Fig 3)
While only one out of two flow diagrams demonstrated the number of records after duplicates removed, 69%, 36% and 78% of papers missed the number of studies included in qualitative synthesis, quantitative synthesis and subgroup analysis, respectively
Summary
Systematic review is a form of literature review that assembles and analyzes several studies related to a specific question, with the aim of synthesizing the respective findings of the studies, basing on the methods framed at the beginning of the procedure [1,2,3,4] It may include a meta-analysis (a quantitative synthesis) depending on the available data [5,6], and provides one of the best evidence of medical research, providing useful clinical data for decision making in actual practice [7,8,9,10]. The adherence to PRISMA checklist should be evaluated for all included systematic reviews and/or metaanalysis [14,15]
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