Reproducibility of Blood Markers of Oxidative Status and Endothelial Function in Healthy Individuals (Technical Briefs‪)‬

Oxidative processes and endothelial cell dysfunction play an important role in the etiology of atherosclerosis. Oxidative modification of LDL in the subendothelial space of the vessel wall is thought to be important in the initiation of atherosclerosis. Oxidized LDL (OxLDL) may not only contribute to foam cell generation, but also stimulate the synthesis of adhesion molecules by endothelial cells. Expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) promotes the adherence and migration of new monocytes through the endothelial barrier to the subendothelial space (1, 2). Finally, some OxLDL will diffuse back from the atherosclerotic arterial wall to the blood, in which it can be measured. Coronary atherosclerosis is associated with increased amounts of circulating OxLDL (3). Circulating ICAM-1, VCAM-1, and von Willebrand factor (vWF) may be regarded as markers of endothelial function, and high concentrations of these markers are predictive of the risk, presence, and severity of vascular disease (4-6). Interest is growing in the measurement of markers of atherosclerosis to predict disease risk and to investigate effects of different interventions. Data on the within-subject variation of these markers are necessary to adequately estimate the required sample sizes for intervention trials and/or the number of blood samples needed to obtain a stable estimate of typical concentrations. However, data on the reproducibility (i.e., within-subject and analytical variation) of oxidative and endothelial markers are still sparse. We therefore investigated the reproducibility of several diagnostic markers of oxidative processes (OxLDL, the endogenous antioxidants bilirubin and uric acid, and ferritin) and endothelial function (sICAM-1, VVCAM-1, and vWF) in healthy individuals. The markers were measured in samples taken on three different occasions within 1 week, and in men and women of different ages.