title: Pediatric reference value distributions for vitamins A and E in the CALIPER cohort and establishment of age-stratified reference intervals.
abstract: OBJECTIVE
  Vitamin A (retinol) and vitamin E (α-tocopherol) are fat soluble micronutrients most commonly measured in the pediatric population to monitor deficiencies due to malabsorption secondary to gastrointestinal (GI) disorders. One of the major challenges of vitamin A and E testing is the lack of reliable pediatric reference intervals which limits accurate interpretation of results. Here we report new pediatric reference intervals (RI) for both vitamins as part of the Canadian Laboratory Initiative for Pediatric Reference Intervals (CALIPER).
  
  
  METHODS
  A total of 342 blood samples were collected from healthy children 1 day to 19 years of age recruited from the community. Retinol and α-tocopherol were extracted from serum using hexane before concentrations were measured with high-performance liquid chromatography (HPLC). Age and sex-specific RI were calculated with guidance from CLSI C28-A2. Non-parametric and robust methods were used to calculate the 95th percentile ranges of the reference intervals along with the 90% confidence intervals.
  
  
  RESULTS
  Vitamin A demonstrated increasing levels with age necessitating four distinct age stratifications. Vitamin E levels peaked within the first year of life requiring only 2 age partitions. Ratios of vitamin E to cholesterol and triglyceride were also calculated, and correlated well to vitamin E levels. Sex-specific differences were not observed.
  
  
  CONCLUSIONS
  This study establishes pediatric RI for vitamins A and E in a healthy population of children from neonates to early adulthood. These values will be beneficial in assessing accurate vitamin status when monitoring children with GI disorders or malnutrition.
authors.affiliation: CALIPER Program, Department of Pediatric Laboratory Medicine, Hospital for Sick Children, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Joshua E
authors.initials: JE
authors.lastname: Raizman
authors.affiliation: CALIPER Program, Department of Pediatric Laboratory Medicine, Hospital for Sick Children, Canada.
authors.forename: Ashley H
authors.initials: AH
authors.lastname: Cohen
authors.affiliation: CALIPER Program, Department of Pediatric Laboratory Medicine, Hospital for Sick Children, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Tracy
authors.initials: T
authors.lastname: Teodoro-Morrison
authors.affiliation: CALIPER Program, Department of Pediatric Laboratory Medicine, Hospital for Sick Children, Canada.
authors.forename: Betty
authors.initials: B
authors.lastname: Wan
authors.affiliation: CALIPER Program, Department of Pediatric Laboratory Medicine, Hospital for Sick Children, Canada.
authors.forename: Man
authors.initials: M
authors.lastname: Khun-Chen
authors.affiliation: CALIPER Program, Department of Pediatric Laboratory Medicine, Hospital for Sick Children, Canada.
authors.forename: Caitlin
authors.initials: C
authors.lastname: Wilkenson
authors.affiliation: CALIPER Program, Department of Pediatric Laboratory Medicine, Hospital for Sick Children, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Victoria
authors.initials: V
authors.lastname: Bevilaqua
authors.affiliation: CALIPER Program, Department of Pediatric Laboratory Medicine, Hospital for Sick Children, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada. Electronic address: khosrow.adeli@sickkids.ca.
authors.forename: Khosrow
authors.initials: K
authors.lastname: Adeli
mesh_terms: D000293:Adolescent; D002170:Canada; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D012016:Reference Values; D014801:Vitamin A / Q000097:blood*; D014810:Vitamin E / Q000097:blood*; D055815:Young Adult
chemical_list: D014801:Vitamin A; D014810:Vitamin E
keywords: CALIPER; HPLC; Pediatric reference intervals; Vitamin A; Vitamin E