BIOLOGICAL VARIATION OF BETA-CAROTENE

The assessment of the normal variation of plasma levels of antioxidant s in healthy individuals is a necessary pre-requisite for accurate int erpretation of the changes that occur in disease states. In this study we determined the analytical (V-A), intra-individual (V-I) and interi ndividual (V-G) components of variation of beta-carotene in plasma, us ing analysis of variance techniques. We studied 12 healthy volunteers (4 women and 8 men) aged 23-45 years. Blood samples were collected bet ween 0800-1000 h every week for 12 weeks, and then monthly for another 3 months. Beta-carotene levels were determined using high performance liquid chromatography. Mean plasma concentrations of beta-carotene de monstrated seasonal variation with a twofold increase from July to Sep tember. Over 12 weeks the mean +/- SD for beta-carotene was 0.54 +/- 0 .15 mu mol/L. The calculated coefficients of variation (CVA, CVI, CVG) were 11, 36 and 39%, respectively. The critical difference (CD) and t he index of individuality (CVI/CVG) were 0.8 mu Mol/L and 0.92. The an alytical goal for beta-carotene was achieved i.e. CVA < 1/2 CVI. The i ndex of individuality was < 1.4 indicating that an individual's refere nce values are more useful than population-based data. The critical di fference for two serial results to be significantly different (p < 0.0 5), was such that at a level of 0.5 mu mol/L an increase of 0.8 mu mol (160%) is required.