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.