As 36 of the drug abuse cases were African-American (86%) and most were male (33/42, 79%), we examined the average statistical significance of differences (Group average p-value, GAP, two-tailed z-test) between drug abuse and control cases for the six drug abuse cases for which both drug abuse and all four control cases were male and of African-American origin (AAM). Even though this analysis employed only ∼1/6 of the 34 drug abuse cases analyzed ( Table 3 ), 37 of 39 transcripts analyzed remained significant at a similar level. For NCLN, the average p-value was 0.22, due to one outlier, but the median was 0.00 for the six AAM cases, indicating that this transcript was similarly changed for most of the cases. For PRKAB1, the average p-value decreased from p = 0.91 for all 34 cases to p = 0.30 for the six AAM drug abuse cases (median p = 0.03). Thus, 38 of 39 transcripts were similarly changed when comparing all cases to the six AAM drug abuse cases. Therefore, the ethnicity of the cases did not exert a major influence on the identification of significantly changed transcripts across drug abuse cases.
