Pediatric within-day biological variation and quality specifications for 38 biochemical markers in the CALIPER cohort.

BACKGROUND Studies of biological variation provide insight into the physiological changes that occur within and between study participants. Values obtained from such investigations are important for patient monitoring and for establishing quality specifications. In this study we evaluated the short-term biological variation of 38 chemistry, lipid, enzyme, and protein analytes in a pediatric population, assessed the effect of age partitions on interindividual variation, and compared the findings to adult values. METHODS Four plasma samples each were obtained within 8 h from 29 healthy children (45% males), age 4-18 years. Samples were stored at -80 °C and analyzed in 3 batches, with samples from 9-10 study participants per batch. Within-person and between-person biological variation values were established using nested ANOVA after exclusion of outliers by use of the Tukey outlier test. Analytical quality specifications were established with the Fraser method. RESULTS Biological variation coefficients and analytical goals were established for 38 analytes. Age partitioning was required for 6 analytes. Biological variation characteristics of 14 assays (37%) were distinct from adult values found in the Westgard database on biological variation. Biological variation characteristics were established for 2 previously unreported analytes, unconjugated bilirubin and soluble transferrin receptor. CONCLUSIONS This study is the first to examine biological variation and to establish analytical quality specifications on the basis of biological variation for common assays in a pediatric population. These results provide insight into pediatric physiology, are of use for reference change value calculations, clarify the appropriateness of reference interval use, and aid in the development of quality management strategies specific to pediatric laboratories.