Tornado diagram

In economic evaluations, tornado diagrams are used to present the result of multiple univariate sensitivity analyses on a single graph. Each analysis is summarised using a horizontal bar which represents the variation in the model output (usually an incremental cost-effectiveness ratio) around a central value (corresponding to the base case analysis) as the relevant parameter is varied between two plausible but extreme values. Typically, the horizontal bars are ordered so that those with the greatest spread (i.e. parameters to which the model output is most sensitive) come at the top of the diagram, and those with the lowest spread come at the bottom. The resulting diagram of stacked horizontal bars has a distinctive tornado shape. Tornado diagrams are used to help the reviewer assess which of the model’s parameters have the greatest influence on its results.