A comparison of the diagnostic performance of the KGM, KSM, and KGM + KSM panels and AFP suggested that HCC-related key species (Odoribacter splanchnicus and Ruminococcus bicirculans) and key metabolites (ouabain, TCDCA, GCDCA, theophylline, and xanthine) may be potential markers for the diagnosis of hepatocellular carcinoma. The gene discussed is AFP; the disease is hepatocellular carcinoma.