More medical journals should inform their contributors about three key principles of graph construction

To identify key principles of graph construction and to review guidance on graph construction provided by medical journals.

Review of a prevailing model of graph comprehension and survey of authors' instructions for all 120 core medical journals as indexed by PubMed.

Graph construction should meet three requirements for optimal graph comprehension: Data symbols should be clearly distinguishable to enable their visual detection. Second, the data should be arranged in such a way that estimation of values and important relationships in the data is facilitated, and third, there should be a full explanation of all graph elements and of how the data were obtained. Seven journals (5.8%) provided recommendations on graph construction. Six journals put emphasis primarily on the explanation of graph elements and, to a lesser extent, on the visual detection of data symbols. Recommendations of the seventh journal focused mostly on how to enhance estimation of important relationships. All journals presented single recommendations whose selection seemed unstructured and not based on key principles of graph construction.

Medical journals should order their instructions according to the three key aspects of graph construction.