BONE MASS ASSESSMENT IN RATS BY DUAL-ENERGY X-RAY ABSORPTIOMETRY

At present there are many techniques available for determining bone ma ss, measurement of which is essential for monitoring osteopenia. Rats are preferred to other laboratory species when designing animal studie s on osteoporosis. The precision and accuracy of dual energy X-ray abs orptiometry (DXA) for the assessment of bone mineral density (BMD) and bone mineral content (BMC) in laboratory animals were assessed. Preci sion, expressed as a coefficient of variation (CV), was measured, maki ng five determinations (Hologic QDR-1000(TM)) on lumbar spine (in vivo ) and femur (in vitro), both with and without repositioning. The corre lation (r) between densitometric parameters and mineral content of bon e ashes was calculated both in lumbar spine (in vivo) and in femur (in vivo). In our study, DXA had good precision, better in femur (CV 0.53 %) than in lumbar spine (L2-L4) (CV 1.0%). Repositioning did not incre ase significantly the coefficients of variation (CV 0.61% and 1.2%, re spectively). The linear regression between BMD and ash weight, calcium and phosphorous content showed high correlation coefficients (r=0.64- 0.85, p<0.05). Although we found an overestimate of values of BMC with respect to ash weight (21% in lumbar spine and 31% in femur), the cor relation between BMC and mineral content was high (r = 0.96-0.99, p<0. 05). The results suggest that the DXA technique has the precision nece ssary when used to assess BMD and BMC in small laboratory animals.