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Vitamin D reference levels varied with race - CALIPER Aug 2013

Marked Biological Variance in Endocrine and Biochemical Markers in Childhood:
Establishment of Pediatric Reference Intervals Using Healthy Community Children from the CALIPER Cohort

Clinical Chemistry September 2013 vol. 59 no. 9 1393-1405
Dana Bailey 1,2,†,
David Colantonio 1,2,†,
Lianna Kyriakopoulou 1,2,
Ashley H. Cohen 1,
Man Khun Chan 1,
David Armbruster 3 and
Khosrow Adeli 1,2,*
1 CALIPER Program, Department of Pediatric Laboratory Medicine, Hospital for Sick Children, and
2 Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada;
3 Abbott Diagnostics, Abbott Park, Chicago, IL.
↵* Address correspondence to this author at: The Hospital for Sick Children, 555 University Ave., Toronto, Ontario, M5G 1X8 Canada. Fax 416-813-6257; e-mail khosrow.adeli at sickkids.ca.

BACKGROUND: Reference intervals are indispensable in evaluating laboratory test results; however, appropriately partitioned pediatric reference values are not readily available. The Canadian Laboratory Initiative for Pediatric Reference Intervals (CALIPER) program is aimed at establishing the influence of age, sex, ethnicity, and body mass index on biochemical markers and developing a comprehensive database of pediatric reference intervals using an a posteriori approach.

METHODS: A total of 1482 samples were collected from ethnically diverse healthy children ages 2 days to 18 years and analyzed on the Abbott ARCHITECT i2000. Following the CLSI C28-A3 guidelines, age- and sex-specific partitioning was determined for each analyte. Nonparametric and robust methods were used to establish the 2.5th and 97.5th percentiles for the reference intervals as well as the 90% CIs.

RESULTS: New pediatric reference intervals were generated for 14 biomarkers, including α-fetoprotein, cobalamin (vitamin B12), folate, homocysteine, ferritin, cortisol, troponin I, 25(OH)-vitamin D [25(OH)D], intact parathyroid hormone (iPTH), thyroid-stimulating hormone, total thyroxine (TT4), total triiodothyronine (TT3), free thyroxine (FT4), and free triiodothyronine.

The influence of ethnicity on reference values was also examined, and statistically significant differences were found between ethnic groups for FT4, TT3, TT4, cobalamin, ferritin, iPTH, and 25(OH)D.

CONCLUSIONS: This study establishes comprehensive pediatric reference intervals for several common endocrine and immunochemical biomarkers obtained in a large cohort of healthy children. The new database will be of global benefit, ensuring appropriate interpretation of pediatric disease biomarkers, but will need further validation for specific immunoassay platforms and in local populations as recommended by the CLSI.

Received for publication January 30, 2013.
Accepted for publication April 9, 2013.

© 2013 The American Association for Clinical Chemistry

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