Variance estimates and individuality ratios of 25 serum constituents in beagles

Variance components and individuality ratios for each of 25 chemical constituents of serum were estimated in a population of beagles. Ten blood samples were obtained from each of 14 beagles, seven of each sex, approximately weekly during three months. Glucose and phospholipid displayed marked inter-dog variation, as compared with intra-dog variation (individuality ratio less than 1). Triglycerides and nonesterified fatty acids had large intra-dog variances relative to their inter-dog variances (individuality ratio greater than 1). Overall, the estimated individuality ratios exceeded 1 for 20 of the 25 constituents. We conclude that subtraction of pretreatment values in the statistical analysis of the data from assays with individuality ratios greater than 1 may mask small clinically or biologically important changes between treatment groups. When the individuality ratio is greater than 1, pretreatment values should only be used as a population screening tool before a study.