Indirect estimation of pediatric between-individual biological variation data for 22 common serum biochemistries.

OBJECTIVES Derivation of between-individual biological variation (CVg) data requires repeat sampling of the same subject, which is undesirable and challenging in children. We describe an indirect sampling (data mining) approach to obtain these data in children. METHODS Twenty-two serum biochemistry results from 6,989 children, who visited their primary care physician in Queensland, Australia, and were tested only twice within a year were included. The CVg and index of individuality of the boys and girls were estimated by year of age, according to the procedures recommended by Fraser and Harris. RESULTS The CVg was generally higher during the first year of life and declined to reach a constant level by age 4 to 6 years, except for aspartate aminotransferase, alanine aminotransferase, γ-glutamyltransferase, and phosphate. The CVg for these tended to increase after age 10 years. Most of the serum biochemistries examined in this study had indices of individuality 0.6 or less, except sodium, anion gap, bicarbonate, and chloride, which ranged from 0.6 to 1.4. The indices of individuality were very stable across all ages. CONCLUSIONS These data are comparable to those reported by the Canadian Laboratory Initiative on Pediatric Reference Intervals study and the Ricos database for adults. This study reports the CVg trends and data for boys and girls by year of age, which have not been described previously.