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Background: The ability to accurately assess antioxidant activity would help monitor oxidation- reduction balance and the occurrence and progress of disease. Thus, the purpose of this study is to establish a combination serum assay for determination of total antioxidant capacity. It is important and also has potential clinical application. Methods: Exogenous oxidants such as iodine (I2), potassium permanganate (KMnO4) and hydrogen peroxide (H2O2) were evaluated in the assay of total antioxidant capacity of serum by employing various detection methods. These methods include electrode potential, microtitration method, and agar diffusion. Based on the evaluation of repeatability, linearity, relative resolution, and detection conditions from seven methods, we found that the combination of three assay methods were optimal to determine total antioxidant capacity of serum from diabetes patients and healthy participants. Results: Precision of the methods was acceptable and good linear relationships were observed between the measured values and the serum percent concentration. We conducted comparative analysis of assay results, i.e., calculation of relative resolution, and finally selected I2/KI and H2O2 electrode potential, and KMnO4 microtitration in combination as an optimized assay of total antioxidant capacity. Total antioxidant capacity of serum from 30 diabetes patients was lower than that of 30 age- and sex-matched healthy participants (P<0.001). Stratification analysis of assay results through the determination of antioxidant capacity allowed to distinguish diabetes patients from healthy participants. Conclusion: The combined use of three assay methods optimized the determination of total antioxidant capacity of serum. It is better to use a variety of methods in the clinical testing.

The purpose of this paper is to develop a new method for determining total antioxidants capacity (TAC) in urine. In our study, Na2S2O3 and mixed urine were used to evaluate the linearity and precision of the iodine starch agar method. The areas of urine diffusion in samples from 44 coronary heart disease patients and 44 healthy subjects were determined by the iodine starch agar method. The results have shown that the linearity and precision for iodine starch agar method were acceptable, because the R2s in linear experiment of Na2S2O3 and urine were 0.999 and 0.995, respectively; variation coefficients of urine diffusion area in high and low levels within-run, between-run, between-day were all less than 10%. The difference of TAC in urine between the coronary heart disease group (Median= 0.95) and healthy group (Median= 1.13) was statistically significant (p=0.001). The iodine starch agar method is a simple and convenient assay to determine total antioxidant capacity in urine.