A subset of cytokines is differentially expressed in the sera of CLL patients compared with healthy age-matched subjects. (A) Levels of cytokines present at significantly higher levels in the sera of CLL patients compared with the sera of healthy subjects are presented as box plots with the bottom and top of the box indicating the 25th and 75th percentiles, respectively. The bar within the box indicates the median value and the ends of the whiskers represent the 10th and 90th percentiles. Outliers are represented by dots. (B) RFA. Cytokines are ranked by their relative importance in discriminating CLL from healthy subjects with CCL3 being the most important predictor of CLL. Only subjects with complete cytokine data (82 total; 31 healthy subjects and 51 CLL patients) were used. Statistical significance was defined as P < .05. For this dataset, the classification error for healthy subjects is 12.9% (4/31) and for CLL subjects 3.9% (2/51). The overall classification error is 7.3% (6/82) keeping the sample size bias or 8.4% [0.5(4/31) + 0.5(2/51)] if we average the 2 error rates. The horizontal axis represents the average decrease in classification accuracy and horizontal bars representing the relative importance of each individual cytokine are sorted by importance along the vertical axis. The horizontal dashed line divides cytokines at the mean value displayed on the horizontal axis and defines the minimum number of cytokines required for maximum classification accuracy.