Sirs We read with interest the article by BanW et al. (2005) suggesting that measuring a number of biomarkers in sport medicine may be useful to a clinician to better assess and evaluate the beneWts of training and/or supplementation programs. Unfortunately, the basic principle and the calculation of the calibration of the commercially available test for reactive oxidative metabolites (ROMs) (d-ROMs test; Diacron; Grosseto, Italy) they used are invalid. In this method, the alchilamine used as a chromogen is also a substrate for ceruloplasmin (ferroxidase) enzyme, which is abundantly present in serum, and the type of the buVer used and its pH are more appropriate for ferroxidase activity. This is borne out by the fact that a signiWcant positive correlation between the assay results and ferroxidase activity has been found (r = 0.911, P < 0.001, n = 100) (Table 1, Fig. 6) (Erel 2005). Also, this assay is inhibited by sodium azide (Fig. 3); no response is observed during copperinduced lipoprotein autoxidation (Fig. 8); and there are no linear appropriate responses for H2O2, t-butyl hydroperoxide or cumene hydroperoxide solutions (Erel 2005). From these data, it is clear that most of the measured absorbance pertains to the activity of ferroxidase, a known antioxidant enzyme, rather than to free oxygen radicals (Erel 2005). Additionally, a clear calibration mistake exists, in that the reported mean serum value for the method is about 300 U Carr/l in healthy subjects (Lindschinger et al. 2004). This value is equal to 7054 mol H2O2/l, a concentration which is about 350 times higher than actual values. Many studies have found that levels of H2O2 above about 50 M are cytotoxic to a wide range of animal, plant and bacterial cells (Halliwell et al. 2000). BanW et al. (2005) state that plasma ROMs, mainly hydroperoxides, were evaluated by performing the dROMs test. However, Erel (2005) has shown that there is a lack of response during copper-induced lipoprotein autoxidation (Fig. 8). Clearly, a more reliable, speciWc and sensitive method is necessary to detect the oxidative status.