[Statistics of bone mineral density determined with a double-energy X-ray equipment]

This study was aimed at analyzing the bone mineral density values measured in a non-selected sample of more than 2,500 Italian women from the Treviso province. The subjects were divided into nine 10-year age groups. The figures (%) in each age group are presumed to be constant over time, although arranged on a Gaussian curve because of high interperson variability. The tables with normal rates, made on the basis of the data obtained, represent the reference parameters to evaluate bone mineral content in all the women referred to our hospital for this particular reason. The tables mirror, with the highest possible accuracy, the typical figures of the female population in Treviso, inasmuch as those findings were obtained from a statistically homogeneous sample (that is, uniform in nature). On the other hand, slight differences were observed relative to the figures of population segments other than our study population. Since the risk of bone fractures is related to how quickly bone mass decreases over time, seriated measurements should be compared with the normal curve which is similar in women of every race. Thus, the tables indicate probable normality whenever the figure found for one woman falls within the normal age and race ranges the patient belongs to. If the patient belongs to a population with different lifestyle and environmental factors, the tables are but indicative; for more accurate evaluation, a late control should be made. On the contrary, if rates are markedly lower than normal, a control should be made much sooner. Moreover, the correlations between the bone density rates found in different bone segments indicate the very poor chance of predicting fracture risk at a different point from the examined one. This means that the body areas at greater risk must be studied separately. Finally, we stress the reason why it is impossible to obtain the very same information from bone mineral content measurements on the whole skeleton and how these data can be used.