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Original article
Laboratory reference intervals in the assessment of iron status in young children
  1. Patricia C Parkin1,2,3,4,
  2. Jemila Hamid5,
  3. Cornelia M Borkhoff1,2,3,4,
  4. Kawsari Abdullah1,3,
  5. Eshetu G Atenafu6,
  6. Catherine S Birken1,2,3,4,
  7. Jonathon L Maguire1,2,3,4,5,7,
  8. Azar Azad8,9,
  9. Victoria Higgins10,
  10. Khosrow Adeli9,10
  1. 1 Division of Pediatric Medicine and the Pediatric Outcomes Research Team (PORT), Hospital for Sick Children, Toronto, Ontario, Canada
  2. 2 Department of Pediatrics, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
  3. 3 Child Health Evaluative Sciences, Hospital for Sick Children Research Institute, Toronto, Ontario, Canada
  4. 4 Clinical Epidemiology and Health Care Research, Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada
  5. 5 Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
  6. 6 Biostatistics Department, Princess Margaret Cancer Center, University Health Network, Toronto, Ontario, Canada
  7. 7 Department of Pediatrics, St. Michael's Hospital, Toronto, Ontario, Canada
  8. 8 Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, Toronto, Ontario, Canada
  9. 9 Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
  10. 10 CALIPER Program, Department of Pediatric Laboratory Medicine,, Hospital for Sick Children, Toronto, Ontario, Canada
  1. Correspondence to Patricia C Parkin; patricia.parkin{at}sickkids.ca

Abstract

Objectives The primary objective was to establish reference intervals for laboratory tests used to assess iron status in young children using the Clinical and Laboratory Standards Institute guidelines. A secondary objective was to compare the lower limit of the reference interval with the currently recommended cut-off value for haemoglobin and serum ferritin in children 1–3 years of age.

Methods Blood samples were obtained from healthy children recruited during scheduled health supervision visits with their primary care physician. For our primary objective, outliers were removed; age partitions were selected and analysis of variance and pairwise comparisons were made between adjacent partitions; reference intervals and 90% CIs were calculated. For our secondary objective, we determined the proportion of children misclassified using the lower limit reference interval compared with the cut-off value.

Results Samples from 2305 male and 2029 female participants (10 days to 10.6 years) were used to calculate age and sex-specific reference intervals for laboratory tests of iron status. There were statistically significant differences between adjacent age partitions for most analytes. Approximately 10% of children 1–3 years of age were misclassified (underestimated) using the lower limit of the reference intervals rather than the currently recommended cut-off values for haemoglobin and serum ferritin.

Implications and relevance Clinical laboratories may consider adopting published paediatric reference intervals. Reference intervals may misclassify (underestimate) children with iron deficiency as compared with currently recommended cut-off values. Future research on decision limits derived from clinical studies of outcomes is a priority.

  • reference intervals
  • decision limits
  • iron deficiency
  • haemoglobin
  • serum ferritin

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/

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Footnotes

  • Contributors PCP conceptualised and designed the study, designed the data collection instruments, interpreted the data, drafted the manuscript, critically revised and reviewed the manuscript for important intellectual content, and approved the final manuscript. JH conceptualised and designed the study, analysed and interpreted the data, critically revised and reviewed the manuscript for important intellectual content, and approved the final manuscript. CMB and KA conceptualised and designed the study, interpreted the data, critically reviewed the manuscript for important intellectual content and approved the final version of the manuscript. EGA performed the statistical analysis, interpreted the data, critically reviewed the manuscript for important intellectual content and approved the final version of the manuscript. JLM and CSB designed the data collection instruments, supervised the data collection, critically reviewed the manuscript for important intellectual content and approved the final version of the manuscript. AA, VH and KA interpreted the data, critically reviewed the manuscript for important intellectual content and approved the final version of the manuscript.

  • Funding Funding to support TARGet Kids! was provided by multiple sources including the Canadian Institutes for Health Research (CIHR), namely the Institute of Human Development, Child and Youth Health and the Institute of Nutrition, Metabolism and Diabetes, as well as the St. Michael's Hospital Foundation. The Pediatric Outcomes Research Team is supported by a grant from The Hospital for Sick Children Foundation. Funding agencies had no role in the design, collection, analyses or interpretation of the results of this study or in the preparation, review or approval of the manuscript.

  • Competing interests None declared.

  • Patient consent Obtained from the parents/guardian.

  • Ethics approval Hospital for Sick Children Research Ethics Board and the St. Michael's Hospital Research Ethics Board.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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