Comparison of spectrophotometric and enhanced chemiluminescent assays of serum antioxidant capacity

Abstract

Background: Over recent years, interest in total antioxidant capacity measurement in biological fluids has increased. A number of assays are now available, and we wished to compare an enhanced chemiluminescence (ECL) method to a spectrophotometric method, the total antioxidant status (TAS) assay. Methods: Serum urate concentration, ECL and TAS were measured in 34 healthy subjects. Additionally, 10 subjects participated in a two-way, randomised crossover study, and received urate 1000 mg or vitamin C 1000 mg intravenously over 1 h. Serum ECL and TAS were measured at 0, 15, 30, 45, 60, 90 and 120 min after commencing infusion. Results: Baseline measurements were poorly correlated between ECL and TAS assays, and between serum urate concentration and each antioxidant assay. There was good correlation between the change in antioxidant capacity detected by both assays during urate infusion ( R=0.79, p<0.001, n=60), but not vitamin C infusion. Conclusions: ECL and TAS measures of serum antioxidant capacity correlate poorly in a healthy population, although both are sensitive to increases in circulating urate concentrations. Therefore, ECL and TAS appear sensitive to different factors. The comparative strengths and weaknesses of various antioxidant assays should be reviewed.