[Difficulties in the interpretation of bone densitometric measurements]

Abstract

In evaluation of the densitometric measurements the most popular presentation of results is a form of t-score or z-score values. T-score is a result of bone mineral density (BMD) in SD below a peak bone mass and z-score is a figure in SD below the values of BMD of healthy individuals of the same age and sex. Osteoporosis is diagnosed if t-score is more than -2.5 ranges from -1.0 to -2.5. Z-score has less value in diagnosis of osteoporosis. The value of different densitometric techniques depends on age of the subject and a past history of fractures. In subjects below 65 yrs the best technique is DEXA (dual energy X ray absorptiometry) and the spine is the site of measurement. In subjects above 65 yrs the best site to measure BMD is the hip. Previous fractures at the site of measurement (vertebral crush fractures), osteoarthritis, kyphosis, could change the values of BMD (overestimate them), and there is a need for a very careful and critical interpretation of BMD results.