Abstract
BackgroundThe data from individual observational studies included in meta-analyses of drug effects are collected either from ad hoc methods (i.e. “primary data”) or databases that were established for non-research purposes (i.e. “secondary data”). The use of secondary sources may be prone to measurement bias and confounding due to over-the-counter and out-of-pocket drug consumption, or non-adherence to treatment. In fact, it has been noted that failing to consider the origin of the data as a potential cause of heterogeneity may change the conclusions of a meta-analysis. We aimed to assess to what extent the origin of data is explored as a source of heterogeneity in meta-analyses of observational studies.MethodsWe searched for meta-analyses of drugs effects published between 2012 and 2018 in general and internal medicine journals with an impact factor > 15. We evaluated, when reported, the type of data source (primary vs secondary) used in the individual observational studies included in each meta-analysis, and the exposure- and outcome-related variables included in sensitivity, subgroup or meta-regression analyses.ResultsWe found 217 articles, 23 of which fulfilled our eligibility criteria. Eight meta-analyses (8/23, 34.8%) reported the source of data. Three meta-analyses (3/23, 13.0%) included the method of outcome assessment as a variable in the analysis of heterogeneity, and only one compared and discussed the results considering the different sources of data (primary vs secondary).ConclusionsIn meta-analyses of drug effects published in seven high impact general medicine journals, the origin of the data, either primary or secondary, is underexplored as a source of heterogeneity.
Highlights
The data from individual observational studies included in meta-analyses of drug effects are collected either from ad hoc methods (i.e. “primary data”) or databases that were established for non-research purposes (i.e. “secondary data”)
Articles were excluded if they met any of the following conditions: (1) were not a meta-analysis of published studies, (2) no drug effects were evaluated, (3) only randomized clinical trials were included in the meta-analysis, (4) less than two observational studies were included in the meta-analysis
The findings of this research suggest that the origin of the data, either primary or secondary, is underexplored as a source of heterogeneity and an effect modifier in meta-analyses of drug effects published in general medicine journals with high impact
Summary
The data from individual observational studies included in meta-analyses of drug effects are collected either from ad hoc methods (i.e. “primary data”) or databases that were established for non-research purposes (i.e. “secondary data”). We aimed to assess to what extent the origin of data is explored as a source of heterogeneity in meta-analyses of observational studies. Existence of heterogeneity in a given meta-analysis is a feature that needs to be carefully described by analyzing the possible factors responsible for generating it [7]. In this regard, the results of a recent study [8] show that whether the origin of the data (primary vs secondary) is explored as a potential cause of heterogeneity may change the conclusions of a meta-analysis due to an effect modification [9]. Considering the source of data as a variable in sensitivity and subgroup analyses, or meta-regression analyses, seems crucial to avoid misleading conclusions in meta-analyses of drug effects
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
