Establishing reference values and evaluation of an in-house ferric reducing antioxidant power (FRAP) colorimetric assay in microplates

Objectives. The total antioxidant capacity (TAC) of a sample can be measured with a ferric reducing antioxidant power (FRAP) assay. There are commercially available kits for FRAP assays, however they are more expensive than in-house kits. We aimed to evaluate a FRAP direct measurement method under our laboratory conditions using a microplate reader and establish reference values to use in future research projects. Methods. An inhouse microplate adaptation of the FRAP method was evaluated. Reference values of FRAP were established for one hundred and twenty subjects aged between 25-55 years. FRAP levels were estimated in 30 serum samples with high glucose concentration, 44 hyperbiluribinemic neonatals and 16 patients receiving renal replacement therapy (RRT). Results. The mean FRAP level was 890±235 μmol/L. The median TAC level was 904 μmol/L. This method was found to be linear up to at least 2000 μmol/L. The intraand inter-assay coefficients of variation were 2.7-6.7% and 5.3-10.1%, respectively. The mean FRAP level was lower than normal in diabetes and RRT patients and higher in hyperbiluribinemic neonatals (687±209 μmol/L, 609±250 μmol/L and 945±187 μmol/L, respectively). Conclusions. Our reference values give comparable results with the literature. This method is simple, reliable, and inexpensive. It could be used for studies of oxidative stressrelated diseases. Eur Res J 2016;2(2):126-131