VOLUMETRIC BONE-MINERAL DENSITY - A POTENTIAL ROLE IN PEDIATRICS

The use of areal bone mineral density (aBMD) in paediatric populations has aroused some concern, as it fails to take the age-related increas e in bone thickness into account. We have developed a measure of true bone density, volumetric bone mineral density (vBMD), which is indepen dent of age and height. In order to examine the relationship between g rowth parameters, aBMD and vBMD, we studied patients with phenylketonu ria (PKU, n = 40), chronic renal failure (CRF, n = 27) and chronic ast hma (n = 19). aBMD of the femoral neck and the mid-femoral shaft was m easured using dual energy X-ray absorptiometry (DXA), vBMD was calcula ted on the basis of values of bone mineral content and bone dimension provided by DXA, with the assumption that both sites are cylinders. aB MD and vBMD were then compared with the normal reference, expressed as a standard deviation score (SDS). aBMD and vBMD were normal in the fe moral neck region of the PKU group, but aBMD, either standardized for age or for height, was low in the femoral shaft region (p < 0.01). In the CRF group, profound growth retardation was seen (mean height SDS, -3.2) and aBMD and vBMD were both low in the femoral shaft region but not in the femoral neck. In the asthma group, aBMD for age was low at both sites, but vBMD did not differ from that seen in normal individua ls. We conclude that the true vBMD provides a different interpretation of bone density compared with aBMD and requires further evaluation in paediatrics because of its age and height independence.