Figure 7.

A graphical representation of the discriminatory potential of discriminant function analysis (DFA). DFA was used to identify, in a cohort of treated patients with juvenile rheumatoid arthritis (JRA) and healthy controls, a subset of genes whose expression values can be linearly combined in an equation, denoted a root, whose overall value is distinct for a given characterized group. The expression values of the individuals in the cohort were plotted in three dimensions to visually represent the relative differences in gene expression among the distinct populations. Gene expression values were plotted on this graph for nine untreated patients with active disease. Five of these nine patients were followed up prospectively during treatment. Four patients responded to treatment and one patient was nonresponsive. The values obtained for the four responsive patients at the time of partial response (after 2–4 weeks of treatment) and full response (6–8 weeks) are shown, as are four independent values obtained from a nonresponsive patient (taken during an 8-week interval). Values for healthy controls are also represented. Values obtained for individuals from each of these groups tended to cluster. Response to therapy was reflected in the spatial relationships among groups.