Independent confirmation and validation across microarray platforms. (A) A new set of data obtained from patients with acute influenza (n = 10) and bacterial infection (S aureus: n = 6; S pneumoniae: n = 6) was analyzed using Affymetrix U133 plus 2.0 GeneChips. The original classifier genes found to discriminate influenza A from bacterial infections (35 genes, Venn diagram, right; Figure 1; Table S3) were used to cluster this new set of samples. (B) A subset of 14 samples from patients with acute respiratory infection included in panel A were clustered using the list of 137 transcripts from Figure 5. (C) Another independent set of samples was obtained from a new set of patients with acute influenza (n = 8) or bacterial infection (S aureus: n = 13; S pneumoniae: n = 3) analyzed using Illumina Sentrix Hu6 whole genome BeadChips. Classifier genes used to discriminate influenza A from bacterial infections (35 genes, Venn diagram, right; Figure 1; Table S3) were used to cluster this new set of samples. Transformed expression levels are indicated by color scale, with red representing relative high expression and blue indicating relative low expression compared to the median expression for each gene across all donors.