MPO and rheumatoid arthritis: In particular, DAS-28 score of RA patients has been correlated with the levels of lipid peroxidation products (Kundu et al., 2012; Datta et al., 2014; Quiñonez-Flores et al., 2016), with the formation of oxidizing species such as O2•, H2O2, •OH and NO (Kundu et al., 2012; Veselinovic et al., 2014; Quiñonez-Flores et al., 2016), as well as the MPO-derived hypochlorous acid [33].