MPO and chronic rhinosinusitis with nasal polyps: Rank and colleagues found that the levels of IL-6, eosinophil major basic protein (MBP), myeloperoxidase (MPO), eosinophil-derived neurotoxin, and uric acid in nasal secretion samples during CRSwNP exacerbation were significantly elevated when compared with the baseline measurements (Rank et al., 2013).