THE ASSESSMENT OF BIOLOGICAL VARIATION COMPONENTS OF COPPER, ZINC, AND SELENIUM

Twelve healthy volunteers (4 women and 8 men aged 23 to 45 years) were assessed for biological variation in copper, zinc, and selenium indic es. Blood was drawn from these individuals once a week for 12 weeks an d then once a month for a further 3 months. Over 12 weeks the mean pla sma concentrations of copper, zinc, and selenium (measured by atomic a bsorption spectrometry), were 16 +/- 2.9, 14.1 +/- 1.5, and 1.28 +/- 0 .13 mu mol/L, respectively. The intraindividual and interindividual co efficients of variation (estimated using analysis of variance (ANOVA) techniques) were 11 and 14% (zinc), 8 and 19% (copper), and 12 and 14% (selenium), respectively. The analytical goal for imprecision was ach ieved for all three micronutrients, i.e., it was less than one-half of the measured intraindividual variation. The indices of individuality for all three elements indicated that an individual's results as refer ence values are more useful than population-based data. The critical d ifference for significance between serial results is relatively smalle r for copper (23%) and zinc (30%) than that for selenium (35%). The mo nthly mean concentrations of the three micronutrients over 6 months de monstrated no seasonal pattern.