Erythrocyte microRNA expression identifies SCD subtypes. (A) The separation of all HbSS patients into 2 groups (HbSS group I, brown, and HbSS group II, red) based on unsupervised analysis of the erythrocyte microRNA expression pattern. (B) The mean expression values of the 83 reticulocyte microRNAs were not significantly different between the 2 HbSS groups (P = .87). (C) The average reticulocyte percentages for group I were significantly higher than group II HbSS patients (P = .001). (D) HbSS subtype classification: training errors are shown as a function of the threshold parameter δ. The value δ = 4.34 is chosen and yields a subset of 6 selected genes and leads to zero error rate. (E) The heat map showing the expression values for the 6 top selected genes in the HbSS groups I and II.