Calculation of Biological Variation Components and Reference Change Value for Serum Copper and Zinc

Zinc and copper are among the most important trace elements. Deficiencies of these trace elements cause a wide variety of disorders. The present study aims to report the definitive assessment of biological variation (BV) parameters for these elements as within-subject BV (CVI), between subject BV (CVG), index of individuality (II), and reference change value (RCV) in a Turkish cohort study group.

Ten blood specimens were collected weekly from 20 healthy volunteers (13 women, 7 men) for 10 weeks. Collected sera were stored at -80°C until the time of analysis. Serum zinc and copper levels were analyzed with atomic absorption spectrometry and ANOVA test was used to calculate the variations.

The CVI and CVG for zinc were 6.26% and 23.27%, respectively. Analytical variation (CVA) was calculated as 4.24%. II and RCV for zinc were calculated as 0.26 and 21.51%, respectively. The CVI and CVG for copper were 6.05% and 19.64%, respectively. CVA was calculated as 4.24%. II and RCV for copper were calculated as 0.31 and 20.47%, respectively.

Since II values were less than 0.6 for both analytes, the reference values will be of little use. RCV might be preferred for better evaluation instead.