Number of above-threshold ratios generated by partially DAP-modified and unmodified target samples. A negative control threshold was imposed to define the lower limit of detection and was calculated by taking the 80% trimmed mean (top 10% and bottom 10% of signals removed from the population) of 216 negative control probes and adding three standard deviations to the mean (99.7% confidence). Embryonic kidney and Burkitt's lymphoma samples were performed in duplicate and data were screened for probes that displayed above-threshold signal intensities. Kidney to lymphoma ratio calls were calculated using only above-threshold probe signals with a maximum of four ratios for each probe. The data represent the average of the number of calls for any two kidney and lymphoma slides +/- standard deviation error bars.