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Quantitative bone analysis in children: current methods and recommendations.

Bonny L Specker·Eckhard Schoenau
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Absorptiometry, PhotonBone DensityBone Diseases, MetabolicBone and BonesChildHumansMass ScreeningTomography, X-Ray ComputedUltrasonographyJournal ArticleReview

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Bonny L Specker, Eckhard Schoenau. 2005. Quantitative bone analysis in children: current methods and recommendations.. https://doi.org/10.1016/j.jpeds.2005.02.002

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PubMed2007

Quantitative bone mineral density assessment in malignant infantile osteopetrosis.

PURPOSE: To investigate the use of quantitative computed tomography (QCT) and dual energy absorptiometry (DXA) for assessing bone mineral density (BMD) in the evaluation of children with malignant infantile osteopetrosis (MIOP). METHODS AND PATIENTS: We retrospectively reviewed QCT- and DXA-determined BMD in six patients with infantile osteopetrosis and correlated BMD measured during the initial evaluation with patient characteristics. RESULTS: Five male and one female infant met the eligibility criteria. BMD was markedly elevated in all patients as determined by each modality, QCT or DXA. For QCT, in which age-specific normal values are known, the BMD was found to be 22.4-32.6 standard deviations above the mean. Using DXA, the estimated BMD of the lumbar spine ranged from 0.45 to 0.8 g/cm(2); children with similarly appearing bone radiographs had quite disparate BMD. While the qualitative trend of BMD among the patients was similar for both measures, the units and numerical values of BMD differed. We found no correlation between BMD results and hematopoiesis observed in the bone marrow or with visual evaluation of the radiographs. CONCLUSION: Both QCT and DXA are effective quantitative measures of BMD in children with MIOP. However, the same modality should be employed for longitudinal evaluation of a given patient. Each technique has unique advantages and disadvantages and may complement one another in the evaluation of MIOP or other bone disorders. Quantitative assessment of BMD in children with MIOP will likely serve to further characterize this disease.

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PubMed2006

Minimum sample size requirements for bone density precision assessment produce inconsistency in clinical monitoring.

INTRODUCTION: Detection of change during bone mineral density (BMD) monitoring is affected by test precision. The International Society of Clinical Densitometry (ISCD) recommends that each center determine precision error using repeat measurements in 30 subjects (or an equivalent method providing 30 degrees of freedom). METHODS: We hypothesized that this sample size may be too small for a robust precision estimate, which could affect the performance of BMD monitoring in clinical practice. Replicate measurements of the spine and total hip (198 spine and 193 hip scan pairs) were obtained (interval 6+/-5 days). The sample was randomly divided into six groups of 30 patients each. Root mean square standard deviation (RMS-SD in g/cm(2)) and coefficient of variation (RMS-CV in %) precision errors and corresponding 95% least significant change (LSC) were calculated for each group and the pooled sample. LSC cutoffs were applied to 1,420 individuals from the Manitoba Bone Density Program who had follow-up measurements on the same instrument (interval 21+/-9 months). While the pooled spine RMS-SD was 0.017 and pooled hip RMS-SD was 0.009 g/cm(2), sample sizes of 30 gave a range of RMS-SD point estimates from 0.012 to 0.021 for the spine and from 0.008 to 0.012 for the hip. RESULTS: When the respective LSC cutoffs were applied to the 1,420 follow-up scan pairs, the fraction of patients categorized with significant change in the spine varied from 20.7% to 46.0%; four of the six LSCs based upon 30 subjects gave fractions significantly different from the pooled LSC of 30.7%. Significant change fractions for the hip varied from 31.1% to 51.1%; two of the six LSCs based upon 30 subjects gave fractions significantly different from the pooled LSC of 40.1%. Similar results were obtained using relative precision errors. CONCLUSION: BMD precision studies using a sample size of 30 are insufficient to reliably characterize precision error or change during clinical monitoring.

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