Flowcharts demonstrate the sequence of activities, processes, events, operations, or organization of a complex procedure or an interrelated system of components. Flowcharts are useful to depict study protocol or interventions (Example F14), to demonstrate participant recruitment and follow-up such as in a randomized controlled trial (CONSORT)8 (Example F15, and Figure 1 in 20.0, Study Design and Statistics), or to show inclusions and exclusions of samples in other types of studies, such as in meta-analyses of observational studies (MOOSE),9 meta-analyses of randomized controlled trials (QUOROM),10 and studies of diagnostic accuracy (STARD).11
Decision trees are analytical tools used in cost-effectiveness and decision analyses.12 The decision tree displays the logical and temporal sequence in clinical decision making and usually progresses from left to right (Example F16). A decision node is a point in the decision tree at which several alternatives can be selected and, by convention, is designated by a square. A chance node (probability node) is a point in the decision tree at which several events, determined by chance, may occur and, by convention, is designated by a circle (see Figure 2 in 20.0, Study Design and Statistics).
Algorithms contain branched pathways to permit the application of carefully defined criteria in the task of identification or classification,13 such as to aid in clinical diagnosis or treatment decisions. Standard box shapes are used to indicate various steps in the algorithm. For example, an oval begins the algorithm with the question to be answered or topic to be addressed. A diamond or hexagon shape indicates a decision box, which has at least 2 arrows leading to different paths in the algorithm. A rectangle or square indicates an action or decision box. Algorithms use arrows to guide readers through the process, and yes and no are marked directly on the pathways (Example F17).
Pedigrees illustrate familial relationships and are often used in the study and description of inherited disorders. Standard symbols are used to indicate each person’s sex, vital status (living or dead), and whether he or she has the condition or genetic component in question, if known. Lines drawn horizontally and vertically between symbols convey relationships, with the earliest generation at the top of the figure (Example F18) (see also 15.6.6, Nomenclature, Genetics, Pedigrees). If the sex of each person is not relevant to the discussion and there may be a concern about identifiability/confidentiality, diamonds or another sex-neutral symbol can be substituted for the standard circles and squares (see also 5.8.3, Ethical and Legal Considerations, Protecting Research Participants' and Patients' Rights in Scientific Publications, Rights in Published Reports of Genetic Studies).