The Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER) reports that it has developed normal reference intervals (RI) for several compounds involved in inborn errors of metabolism (IEM).

“Understanding age- and sex-specific biological changes in metabolic disease biomarkers is essential for their appropriate utilization in management of children with [IEM],” stated an article in Clinical Biochemistry that describes CALIPER’s findings. Clinicians use RIs or normative data to assist in the interpretation of biochemical markers that monitor and diagnose childhood disease.

The Clinical Laboratory and Standards Institute’s (CLSI) C28-A3 guidelines describe a protocol to establish RIs, yet accomplishing this isn’t easy. It requires a large sample population, and the process of collecting samples and doing data analysis also poses some challenges. CALIPER, whose charge is to develop comprehensive pediatric RIs, to date has recruited 8,500 healthy children and adolescents across Canada, and has managed to establish RIs for more than 85 analytes ranging from endocrine hormones, chemistry assays, and routine biochemical markers.

“The CALIPER project has refined our vision of pediatric reference intervals for a large number of circulating biochemical markers,” observed author Dennis Dietzen in a related editorial in Clinical Biochemistry.

Gaps, however, have been found in RIs for IEM, a series of rare genetic diseases that impact metabolic pathways such as carbohydrate metabolism and fatty acid oxidation, and usually appear shortly after birth. Serious health consequences can result if IEMs aren’t detected or treated.

Using the CLSI C28-A3 guidelines, CALIPER recruited 500 healthy individuals ranging in age from birth to 19 years from its study population to develop robust childhood RIs for several key IEM biomarkers: serum amino acids, acylcarnitines, total and free carnitine, and free fatty acids and β-hydroxybutyrate.

“To the best of our knowledge, comprehensive pediatric RIs for amino acid and acylcarnitine profiles in an exclusively healthy and nonhospitalized pediatric cohort have not yet been established across the entire pediatric age range,” the authors of the study noted.

CALIPER has done similar work in this area—in August, CLN Stat reported on the studies it conducted with the Canadian Health Measures Survey, which provided new insights on age-specific reference intervals for 53 hematology, immunoassay-based special chemistry and endocrinology, and biochemistry biomarkers.

For the IEM study, researchers used serum samples to measure the IEM biomarkers, incorporating various technologies such as ultra-performance liquid chromatography, tandem mass spectrometry, and the Vitros 5.1 chemistry analyzer. Using non-parametric statistics, they then established age- and sex-specific pediatric RIs.

“Approximately 80% of all analytes required 2 to 4 age-dependent partitions, with over 50% of amino acids and over 70% of acylcarnitines exhibiting significant physiological changes during the neonatal period. Also, 21% of all analytes required partitioning during puberty and adolescence, half of which produced sex-specific distributions,” the authors summarized in the article.

In the short term these results will improve the assessment of children with suspected metabolic disorders and in the long term may improve the practice of pediatric medicine in ways that we don't yet realize,” Dietzen predicted.