One of the most common oxidation which may be found in nature is the formation of rust from iron. In this process the iron passes from its original metallic state to that of ferrous oxide, or even ferric. In technical terms we say that the iron is transformed from its elemental state (Fe⁰) to that of ferrous ion (Fe²⁺) or ferric (Fe³⁺), typical of their "oxides." This happens every time the iron is in direct contact with an oxidizing agent that is able to snatch two or three electrons respectively. It is evident that any agent capable of bringing iron from its ferric to the ferrous state can be regarded as a reducing agent and, in this context, an antioxidant.

On this basis, the BAP Test tests for the determination of biological antioxidant potential (Biological Antioxidant Potential) is a photometric test, which allows to determine the blood concentration of antioxidants in their sense of agents capable of reducing the iron from ferric to the ferrous form. So conceived, the BAP Test provides an overall measure of many antioxidants such as bilirubin, uric acid, vitamins C and E and proteins.

In healthy subjects the BAP Test assumes a value higher than 2200 micromol/L is considered as the optimum value. In normal practice in 1 mL of plasma has an antioxidant potential to reduce 2.2 micromoles of iron per liter. Values less than 2200 micromoles/L are indicative of a condition of oxidative stress by lowering of antioxidant defenses. In this case, will the physician should determine, through the inclusion of test results in the clinical picture of each specific patient, what strategy should be put in place in order to bring back to normal any outliers.

In principle, values lower than optimum can be observed in case of unbalanced diet or under conditions of excess free radicals. Compared to OXY-Adsorbent Test, the BAP measures the "dynamic" or "biologically active" component of the antioxidant plasma barrier. For this reason, it has a good application in evaluating the effectiveness of the antioxidant activity of substances lower molecular weight, or at least a more rapid turnover, such as ascorbic acid, uric acid, bilirubin, etc.. The OXY-Adsorbent Test, however, provides information on the “structural" component of the antioxidant barrier (proteins and other compounds with high molecular weight) of which the period of "recovery" is relatively slow.