Comparison of predicted phenotype frequencies between the Serbian and European subpopulations from the 1000 Genomes Project (Central European–CEU, Finnish–FIN, Great Britain–GBR, Tuscans from Italy–TSI and Iberian Spanish–IBS) (Sherman, Claw, and Lee, 2024) was performed for 12 pharmacogenes (ABCG2, CYP2B6, CYP2C19, CYP2C9, CYP2D6, CYP3A5, DPYD, IFNL3, NUDT15, SLCO1B1, TPMT and UGT1A1) and for 10 pharmacogenes in the Croatian population (CYP2B6, CYP2C19, CYP2C9, CYP2D6, CYP3A5, DPYD, NUDT15, SLCO1B1, TPMT and UGT1A1) (Supplementary Data Sheet 9). The gene discussed is IFNL3; the disease is irritable bowel syndrome.