While many cytokines in nasal secretion showed higher expression in refractory CRSwNP, including T2 inflammatory cytokines, IL-3, IL-5, IL-25, IgE, and GM-CSF (P = 0.020, 0.009, 0.004, <0.001, and 0.002, respectively), and neutrophilic inflammatory cytokines, IL-8, MPO, and G-CSF (P = 0.031, 0.010, and 0.038, respectively) (also as T3 inflammatory biomarkers), IL-2, and IFN-γ (all P < 0.001) (also as T1 inflammatory biomarkers), than those in control subjects. Here, MPO is linked to chronic rhinosinusitis with nasal polyps.