As for STAT1 and GBP1, the validity of the rule ‘PSMB9 high in RA’ is emphasized by the fact that it appears in three different rule sets (rule set ‘Berlin’, position 13; rule set ‘Leipzig’, position 17; rule set ‘Total’, position 1; see Table 5 and Additional file 4). The gene discussed is STAT1; the disease is rheumatoid arthritis.