A Comparison Between Two Assays for the Redox Status in Plasma

The redox status is an important tool in determining the physiological state of the body, especially for the elderly and with hypertension and heart failure [1-4]. A reflection of the redox status in the circulation can be measured by the level of free thiol groups in proteins in serum or plasma samples. There are several assays described in the literature for the evaluation of the redox status in serum or plasma. In these simple assays, a reaction of thiol groups of proteins takes place with a chromogen. The most used assay is based on the reaction of 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB), with thiol groups which can be easily performed with home-made materials [5,6]. However, for quality control during large-scale studies, commercially available assays are preferred due to the long-term delivery and stability of the assay components and the availability of quality control materials. This test can be performed either by high performance liquid chromatographic methods [7-9] or in micro plate format [10] and was also programmed and applied to clinical analyzers [11-14]. The use of auto-analyzers allows measurement of large sets of samples in epidemiological studies under the required quality during longer periods. Another advantage is the possibility to combine the assay with the measurement of other biomarkers in the same small volume of sample [15].