Background: To date, China has no industry standard for reference intervals (RIs) of paediatric blood biochemical markers. This study aimed to evaluate changes in biochemical markers in the venous blood of healthy children aged 29 days to 12 years, derived from the UniCel DxC 800 system, and establish appropriate RIs.

Methods: We analysed venous blood from 1980 healthy children for 20 biochemical markers. RIs were established according to the Clinical and Laboratory Standards Institute C28-A3c guideline and compared with those of adults in China.

Results: All markers except for sodium and chlorine required partitioning by age, but not by sex. The RIs of total protein, albumin, globulin, carbon dioxide, urea nitrogen, creatinine, and uric acid consistently increased with age in children, but were always lower than those of adults. Children aged 29 days to 12 years had a single combined RI for sodium and chloride, respectively; although the RIs in children were similar to those of adults, their upper limits were lower. The RIs of direct bilirubin, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, potassium, calcium, magnesium, and phosphorus continued to decline with age. The RIs of total bilirubin, indirect bilirubin, and gamma-glutamyl transpeptidase initially declined followed by a slight rebound.

Conclusions: While establishing RIs, most markers required partitioning by age (aged 29 days to 12 years); the partitioning scheme differed for each marker, and paediatric RIs differed from those for adults. It is therefore necessary to establish separate paediatric RIs.