Vitamin D Deficiency and Insufficiency in Children With Osteopenia or Osteoporosis: In Reply

Abstract

We appreciate the comments by Rovner and Miller but still propose that the methods used in conducting and reporting our study were appropriate. As we acknowledged in our study methods section, there is still no consensus criteria for the level of bone mineral density (BMD) deficit (as defined by z score) that should define osteopenia or osteoporosis in pediatric patients. As was emphasized, we included only children with evidence of clinical bone fragility as manifested by fractures. This is consistent with the International Society for Clinical Densitometry (ISCD) 2007 pediatric official positions,1 which state that the “diagnosis of osteoporosis requires the presence of both a clinically significant fracture history and low bone mineral content or bone mineral density.”Drs Rovner and Miller cite the ISCD 2007 guidelines that recommend using the terms “low bone density for chronological age” or “below the expected range for age” if a z score is below −2.0.2 We would like to point out that this recommendation applies to the suggested language for pediatric dual-energy radiograph absorptiometry (DXA) reports, in which the terms “osteopenia” and “osteoporosis” should not appear without knowledge of clinically significant fracture history. This is irrelevant in characterization of our patients, because we knew that their fracture history raised clinical suspicion for osteoporosis.We used the terms osteopenia and osteoporosis to reflect the wide range of low bone density seen in these children. All of our patients had a significant fracture history. Only 4 of our patients, all with osteoporosis imperfecta, had a normal lumbar BMD z score (ie, above −1.0), which supports the statement that the diagnosis of osteoporosis in children should not be made on the basis of densitometric criteria alone.1 For purposes of this report, we used the definition of osteopenia as a BMD z score of less than −1.0, as have other investigators in pediatric bone studies.3–5 We agree that the BMD definition of osteoporosis should now conform to the recently published 2007 ISCD recommendation.1 With regards to the z-score determination, we used our institution's normative data, which were based on the 1991 report by Southard et al6 using the Hologic DXA. There have been >30 pediatric normative data for DXA published to date.2As noted in the article, we found no associations between vitamin D levels and fractures in these children and agree that a control group would be required to determine any true association. We agree also that there needs to be caution in drawing conclusions about low bone mass and vitamin D status. We simply postulate that low vitamin D levels may contribute to low bone mass or worsen the fracture risk in these children, because there was an inverse relationship between 25-hydroxyvitamin D level and several different bone parameters, such as parathyroid hormone level. Much work remains to be done to fully define these important relationships in children with low bone mass.