The significance and methods of assessment of blood parameter variability in veterinary medicine

Abstract

Changes within an individual during re-evaluation within a certain period are referred to as intraindividual variations, and they are determined by the intraindividual coefficient of variation (CVi), which indicates the degree of variability of the sample results in comparison to the population's arithmetic mean. A higher CVi denotes less stability of the investigated parameter and greater variability within the individual. By calculating CVi from repeated measurements, one can estimate how much the measured parameters fluctuate in an individual over time. The ratio of individual and group biological variation represents the index of individuality (IoI) for the examined analyte. This index determines whether it is more appropriate to use population-based reference intervals or subject-based reference intervals for a particular analyte, i.e. predicts the utility of the reference intervals. It also suggests that if intraindividual biological variation is greater than interindividual variation, (individuality index is ≥ 1.4), population-based reference intervals will be most useful for all individuals. If intraindividual biological variation is less than the interindividual variation (individuality index is ≤ 0.6), then the RCV value (reference change value, or RCV) should be used. Calculating the RCV value is a method used to determine whether the difference in two consecutive analyses is significant and biologically relevant, taking into account factors related to laboratory activity (preanalytical and analytical error), as well as factors related to normal intraindividual biological variation. Finally, determining the number of samples required for assessing the homeostatic setting point is another method used to evaluate intraindividual variability. In veterinary medicine, it is essential to understand the intraindividual variability of blood parameters to accurately diagnose patients and monitor their health. Subtle changes over time that may suggest a progression or regression of the disease can be detected by the use of intraindividual variability methods. Additionally, the response to treatment can be monitored and, if necessary, adjusted.