Clinical Applicability of the Bone Mineral Content Measured by Monoenergetic Photon Absorptiometry

摘要

Bone mineral content (BMC) measurements were employed in two basic types of studies. In the first type, measurements made on an individual patient are used to trace the time variation in body calcium. In the second type, mineral content of an individual is determined and compared to a standard value. Generally, the standards provided are derived from normal populations grouped by the parameters of age and sex (mean value denoted BMC/sub m/). However, the parameter of skeletal size has generally not been used, on the assumption that the BMC value obtained is a true density measure. The BMC measure is, however, a linear density measure; hence it is essential to use skeletal size as a parameter. The clinical usefulness of relative BMC obtained with the parameters of sex, age and body habitus is evaluated. The normal value (BMC/sub p/) is obtained by an algorithm utilizing values of sex and age, and also height and lean body mass (as derived from exp 40 K measurement). The latter two components characterize skeletal size and body habitus, respectively. For the study, 119 white women were selected from a larger population. Additionally, these women were judged (on the basis of total body neutron activation analysis) to have calcium levels in the normal range. On the basis of physical and roentgenological examination, individuals with evidence of metabolic calcium disorders or osteoporosis were excluded. The variance of BMC values of these individuals, when expressed in terms of BMC/sub p/, was significantly less than when expressed in terms of BMC/sub m/ (p = 0.95 - 0.99 as determined by ''F'' statistic in analysis of variance). Erroneous conclusions on Ca deficit or excess can be drawn for individuals whose height and body size differ markedly from the average, as the variation of their BMC values often exceeds the variation in the mean group. (ERA citation 04:001452)