Clustering of rheumatoid arthritis patients as responders versus non-responders. Transcripts in peripheral blood mononuclear cells from six responders (R) or seven non-responders (NR) who were included in two training subsets (subset 1 in text and Tables 2 and 3) were studied by microarray analysis. Informative transcripts as selected by a statistical analysis (t test, 25 transcripts; significance analysis of microarrays (SAM), 37 transcripts) were next used for an unsupervised hierarchical clustering of the same 13 patients, listed as columns. The gene names are listed as rows (expressed sequence tags are noted with a plain, five to six digit IMAGE clone number). The genes are underlined whenever they were selected by both SAM and t test. Transcript levels are expressed as ratios (level in sample/level in internal, arbitrary standard). Scale bar (log2 ratio): decreased (green), increased (red) or identical (black) ratio in sample versus standard (grey squares are missing values).