Clinical Trials

Clinical Trials: A Practical Guide ■❚❙❘Figure 11. A spaghetti plot showing individual pharmacokinetic concentration profiles in a study.3,000Concentration (ng/mL)2,0001,00000 2 4 6 8 10 12 14 16 18 20 22 24Hours after dose administrationForest plotsA forest plot displays point estimates and the corresponding confidence intervals(CIs) for multiple groups. Forest plots are most commonly used to presentsubgroups within a trial or the results of multiple studies as part of a metaanalysis,which is a formal method of comparing the results of several trials usingthe same intervention (see Chapter 38). Point estimates are usually obtained fromsimple or extended regression models such as logistic regression. In a systematicreview of randomized controlled trials investigating the effects of corticosteroidson mortality in individuals with brain trauma, 13 trials were combined in a metaanalysisand the odds ratios of each study were presented using a forest plot(Figure 12) [5].In this graph, the size of the marker represents the size of the corresponding studyand the central vertical line represents no difference between the treatment andcontrol arms. In meta-analyses, forest plots typically include a diamond at the baseof the graph representing the combined estimate, or pooled intervention effect,from all of the studies. The center of the diamond corresponds to the pooledpoint estimate, and its horizontal tips represent the CIs based on the formalmeta-analysis. While it is common to use 95% CIs for each trial and for the overall421