Evaluation of a novel colorimetric assay for free oxygen radicals as marker of oxidative stress

Background: Free oxygen radicals play an important role in the pathogenesis of many diseases including cardiovascular disease, diabetes, hypertension, cancer and aging. Several methods were developed for the direct or indirect measurement of oxygen free radical and its byproducts. The free oxygen radicals monitor (FORM) is a novel point-of-care system for the rapid measurement of free oxygen radicals (FORT) in blood. We have carefully evaluated the use of this assay for batch analysis of plasma samples in a research environment with respect to factors affecting its performance, including storage temperature and duration. Methods: We determined the effect of storage, hemolysis, variability and reproducibility of the FORT in blood and plasma. Results: Plasma FORT correlated significantly with hsCRP (P<0.0001) and CHOL/HDL ratio (P<0.02). While hsCRP results have shown a greater range of assay variability (27.82%-53.92%), FORT measurements in the same samples have less assay variability (5.63%-9.61%). Collected whole blood can be kept on ice for up to 7 h prior to plasma isolation without affecting FORT values. Storage of plasma has no effect on FORT when stored at 4 degrees C for up to 3 weeks (R-2 = 0.685). Comparable values can be obtained in samples stored for up to 3 months at -80 degrees C (R-2 = 0.5888) but not at -20 degrees C. Conclusions: The day to day variability of FORT, as assessed by multiple measures in a group of controls over time, is minimal. FORT assay is stable when stored at -80 degrees C for a couple of months or at 4 degrees C for a few weeks. FORT correlation with hsCRP and other lipid markers provides an interesting insight and a novel link between oxidative stress, inflammation and lipid metabolism. (C) 2008 The Canadian Society of Clinical Chemists. Published by Elsevier lnc. All rights reserved.