The accurate assessment of oxidative stress in biological systems is a problem for all investigators working on the role of free radical damage in disease. Numerous assays have been described to measure various free radical damage products or antioxidant status, and the plethora of available techniques attests to the fact that no ideal method is available. The concept of a single test that might reflect total antioxidant capacity (TAC) is an attractive one, and in this issue Koracevic et al describe one such test.¹ Low total antioxidant capacity could be indicative of oxidative stress or increased susceptibility to oxidative damage.

The idea of a single measurement of total antioxidant capacity is not a new one. Wayner et al in 1985 described the total radical trapping parameter (TRAP) assay, based on the generation of peroxyl radicals from 2,2`-azobis (2-amidinopropane) dihydrochloride (AAPH).² After adding AAPH to a …