Neighborhood analysis of normal CD34⁺ cells versus early MDS CD34⁺ cells of the initial data set of 14 low-risk MDS and 9 healthy controls. The plot shows the number of probe sets predictive of MDS (black diamonds) versus normal together with curves showing the 50% (thick solid line), 5% (thin solid line), and 1% (dashed line) significance levels representing randomly permuted class distinctions. There is a less than 1 in 100 chance of probe sets to the left of the dashed line falsely predicting MDS. Eighty-nine underexpressed probe sets distinguish MDS from normal (A), whereas no overexpressed probe set in MDS can make the distinction between MDS and normal (B).