Data Extraction from Graphs Using Adobe Photoshop: Applications for Meta-Analyses

Graphs, an effective form of data presentation, are used for summarizing complex information and making them easier to understand. Extracting numerical data from graphs, which is commonly required in systematic reviews and meta-analyses, is however a challenging issue. Since this kind of results presentation is common, ignorance of such data may result in publication bias when conducting meta-analyses. On the other hand, contacting the authors of a particular publication in order to retrieve the data may take a long time and is often not very fruitful. In this case, there are a few software and methods that may be used for data extraction; however, using these software is costly and not simple as well as different types of graphs need different extraction methods. Here, we have described a simple reproducible method for extracting data from graphs using Adobe Photoshop.