INTERPRETATION OF BONE DENSITOMETRY STUDIES

Dual-energy x-ray absorptiometry (DXA) is widely used for identifying patients with osteoporosis. making decisions about the commencement of preventive therapy, and following up response to treatment. It is imp ortant that radiologists and nuclear medicine physicians issuing clini cal reports present clear interpretations that aid the primary care ph ysician in making decisions affecting treatment. This review discusses the principles behind the interpretation of bone mineral density (BMD ) studies. After a World Health Organization report published in 1994. osteoporosis is often diagnosed on the basis of the patient's T-score value (difference of BMD from young adult mean normalized to the popu lation SD). T-scores are a measure of current fracture risk. There are problems relating to the use of T-scores in the elderly. and we argue that decisions about treatment are generally best made on the basis o f the Z-score value (difference of BMD from age-matched mean normalize d to the population SD) because this measures the patient's fracture r isk relative to his or her peers, Recent studies confirm that the post eroanterior (PA) projection lumbar spine scan is still the optimum mea surement site for monitoring response to treatment, A BMD change of 4. 5% is required to register a statistically significant change. Copyrig ht (C) 1997 by W.B. Saunders Company.