To determine whether genes differentially expressed in peripheral blood cells could be used for diagnostic screening, we selected 13 (EMR1, IFI27, PLCB2, RARA, SORL, STAT1, ABCG1, C15orf39, LYN, PLEKHG3, ATG2, MME, DEFA1), 15 (MME, FOXO3, DBI, IFI27, HSPE1, BOLA2, ABCG1, PLCB2, DYSF, CLC, PRSS33, RAP1, GAP, RNF182, RPS28), and 7 (OPLAH, ALPL, SLC26A8, PFKFB3, MMP25, TLR5, DYSF) genes with expression levels significantly altered in patients with PBC, PSC, and IBDs, respectively, compared with healthy controls. The gene discussed is ABCG1; the disease is primary biliary cholangitis.