Clinical Trials

❘❙❚■ Chapter 36 | Use of FiguresTable 1. Number of patients (%) with protocol-defined virological failure in both treatment arms of theMaxCmin 1study.Reason failed Indinavir/r Saquinavir/rn = 158 n = 148Virologically 33 (20.9) 25 (16.9)Lost to follow-up 8 (5.1) 8 (5.4)Withdrew consent 1 (0.6) 3 (2.0)Died 1 (0.6) 1 (0.7)Total 43 (27.2) 37 (25.0)r = ritonavir.Commonly used graphs in clinical researchThe choice of graph that will best fit the data depends on the distribution of the data(categorical or continuous) and the number of variables under consideration. Sincecategorical data consist of unique categories (eg, male/female) where each categoryis usually observed more than once, and continuous data contain distinct values(eg, height in cm) where each specific value appears infrequently, we use differentmethods for displaying each type of data. The most commonly used graphs todisplay single discrete numeric variables or categorical data are bar charts, piecharts, dot plots, and stem-and-leaf plots. Continuous data are usually displayedusing histograms, dot plots, box plots, scatter plots, and line graphs, althoughcontinuous data are sometimes grouped in order to use graphical methods forcategorical data. These graphs are described in detail in the following sections.Bar chartsBar charts can only be produced when the variable of interest is categorical ordiscrete numeric. They frequently occur in publications because they are visuallyvery strong, useful for comparing more than one group, and easy to produce andinterpret. Bar charts are produced by calculating the number of observations ineach category; these observations are then translated into frequencies (orpercentages), where the length of each bar is proportional to the frequency ofobservations in that category. Labels can be added to each bar to show the totalnumber of patients contributing to that category. The bars on the bar chart aretypically separated by gaps to indicate that the data are discreet.In the MaxCmin 1study, protocol-defined virological failure was broken down intotrue virological failures, patients who were lost to follow-up, patients whowithdrew consent, and those who died (Table 1). These data can be presented intwo ways using a bar chart:410