PEDIATRICS Vol. 122 No. 4 October 2008, pp. 907-908 (doi:10.1542/peds.2008-1743)
LETTER TO THE EDITOR |
Vitamin D Deficiency and Insufficiency in Children With Osteopenia or Osteoporosis
Alisha J. Rovner, PhDDivision of Epidemiology, Statistics and Prevention
Eunice Kennedy Shriver National Institute of Child Health and
Human Development
Bethesda, MD 20892-7510
Ryan S. Miller, MD
Divisions of Metabolism and Pediatric Endocrinology
Johns Hopkins University School of Medicine
Baltimore, MD 21287
To the Editor.—
In the study by Bowden et al,1 vitamin D status was reported for 85 children referred to a pediatric metabolic bone clinic. The authors concluded that "vitamin D insufficiency is common even in children with recognized osteopenia and osteoporosis caused by primary metabolic bone disease or secondary to chronic illnesses." Although interesting and provocative, several methodologic flaws raise concerns about the validity of their findings and conclusions.
One major concern is their use of the terms osteopenia and osteoporosis. Despite acknowledgment from the authors that there are no consensus criteria based on bone mineral density (BMD) for osteopenia or osteoporosis in children, they arbitrarily use lumbar spine BMD z scores between –1.0 and –2.0 to define osteopenia and less than –2.0 to define osteoporosis. A BMD z score between –1.0 and –2.0 is considered within the normal range for children. The definitions they use are contrary to guidelines published by the International Society for Clinical Densitometry,2 which recommend using the terms "low bone density for chronological age" or "below the expected range for age" if a z score is less than –2.0.
We are also concerned that errors were made in adjusting raw BMD data to generate the z scores. For children with delayed linear growth and/or maturation, the International Society for Clinical Densitometry has recommended adjusting areal BMD for absolute height or height age, or comparing BMD to pediatric reference data that provide age-, gender-, and height-specific z scores. Although the authors did adjust BMD for weight and pubertal status, they did not adjust for height, which likely misclassified a number of children. Misclassification of low bone mass as a result of misinterpretation of dual-energy radiograph absorptiometry results or improper use of reference data has been reported in pediatric populations.3,4
Last, the data do not allow conclusions to be drawn regarding the relationship between low BMD and vitamin D status, because all children referred to the bone clinic were included in the study, not just those with low BMD. In addition, because there was no control group and hypovitaminosis D is quite common in healthy children,5 the finding that 80% of the subjects had 25-hydroxyvitamin D concentrations of <30 ng/mL informs us minimally regarding the relationship between vitamin D status and low BMD.
Although the Bowden et al study demonstrated that hypovitaminosis D was common in children referred to a metabolic bone clinic, one cannot draw conclusions regarding relationships between vitamin D levels, low BMD, and pediatric bone disease. Such a finding would require a study with an appropriate control group, uniform subject population, and accurate definitions of low BMD. We appreciate the authors bringing attention to this topic; however, we urge readers to evaluate their results with caution given the limitations highlighted above.
REFERENCES
- Bowden SA, Robinson RF, Carr R, Mahan JD. Prevalence of vitamin D deficiency and insufficiency in children with osteopenia or osteoporosis referred to a pediatric metabolic bone clinic. Pediatrics. 2008;121 (6). Available at: www.pediatrics.org/cgi/content/full/121/6/e1585
- Gordon CM, Bachrach LK, Carpenter TO, et al. Dual energy x-ray absorptiometry interpretation and reporting in children and adolescents: the 2007 ISCD Pediatric Official Positions. J Clin Densitom. 2008;11 (1):43 –58[CrossRef][Web of Science][Medline]
- Gafni RI, Baron J. Overdiagnosis of osteoporosis in children due to misinterpretation of dual-energy x-ray absorptiometry (DEXA). J Pediatr. 2004;144 (2):253 –257[CrossRef][Web of Science][Medline]
- Leonard MB, Propert KJ, Zemel BS, Stallings VA, Feldman HI. Discrepancies in pediatric bone mineral density reference data: potential for misdiagnosis of osteopenia. J Pediatr. 1999;135 (2 pt 1):182 –188[CrossRef][Web of Science][Medline]
- Rovner A, O'Brien K. Hypovitaminosis D in healthy children: a systematic review of the evidence.
Arch Pediatr Adolesc Med. 2008;162
(6):513
–519
[Abstract/Free Full Text]
PEDIATRICS (ISSN 1098-4275). ©2008 by the American Academy of Pediatrics
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