Evaluation of oxidative status in human serum: comparison of different methodological approaches

Different biomarker assays have been developed for assessing oxidative stress in human serum. In this retrospective study the analytical performance of two different methodological approaches was evaluated in subjects with known increased oxidative stress to measure serum peroxidation indices: mild (n=35) and heavy (n=61) smokers, chronic renal failure (n=19) and kidney transplanted patients (n=59) compared to healthy controls (n=56). Serum oxidative stress, assessing Reactive Oxygen Metabolite derivatives (d-ROMs, Diacron International, Italy) levels and Total Antioxidant Capacity (TAC, Diacron International, Italy) by commercial spectrophotometric assays, was compared with malondialdehyde (MDA) concentrations, quantified both in free (FMDA) and total (T-MDA) forms, by isotope-dilution gas chromatography-mass spectrometry (GC-MS) technique (“gold standard” reference method), generally unsuitable for routine use. Sensitivity, specificity and cut-off points of T-MDA and F-MDA, d-ROMs, TAC assays were evaluated by receiver-operator characteristic (ROC) analyses together with the area under ROC curve (AUC). ROC analyses accuracy: the best for T-MDA (AUC: 1; sensitivity and specificity: 100%), good for d-ROMs (AUC: 0.87; sensitivity 72.8%, specificity: 100%) and F-MDA (AUC: 0.82; sensitivity 74.7%, specificity: 100%), and not as good as the previous for TAC (AUC: 0.66; sensitivity: 52% and specificity: 92.9%). The increased peroxidative damage was best proved only by T-MDA levels. The assessment of d-ROMS concentrations and TAC by reliable assays is useful for routine clinical purposes; even if less sensitive, it determines the balance of oxidative status. The comparison between “gold standard” and routine methods allows biochemists and clinicians to evaluate data more thorough.