Dual-energy x-ray absorptiometry of the rat: Accuracy, precision, and measurement of bone loss

<div class="line" id="line-9"> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> Dual&hyphen;energy x&hyphen;ray absorptiometry (DEXA) is now an established method of measuring bone mineral density (BMD) in humans. We have applied the technique to measuring BMD in the rat. The short&hyphen;term precision of the technique was assessed by calculating the BMD coefficient of variation at the rat spine (1.20%), total femur (0.52%), proximal femur (1.16%), midfemur (1.00%), distal femur (0.96%), and proximal tibia (2.2%). The long&hyphen;term precision of femoral measurements in rat cadavers over a 4 week period was 0.72% for the total femur and 1.2% for the distal femur. The accuracy of the technique was assessed by comparing DEXA&hyphen;measured bone mineral content (BMC) in vitro and in vivo with ashed BMC. Results indicated a highly significant positive correlation between in vitro DEXA measurements and ash BMC ( </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> r&nbsp; </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> = 0.99) and between in vivo DEXA measurements and ash BMC ( </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> r&nbsp; </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> = 0.89). The ability of the technique to detect bone loss was assessed at the femoral site by comparing the BMD of ovariectomized (OVX) and sham&hyphen;operated rats at baseline and at a 1 month follow&hyphen;up. There was no significant difference in BMD between the groups at baseline. However, at 1 month follow&hyphen;up the OVX group showed a significant ( </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> p&nbsp; </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> &lt; 0.001) decline in BMD at the distal femur (&hyphen;8.6%) and in the total femur (&hyphen;4.8%) compared with sham&hyphen;operated rats. A comparison of retired breeder female rats with age&hyphen;matched nulliparous rats indicated that the BMD of retired breeder rats was significantly lower than that of virgin females at all femoral sites ( </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> p&nbsp; </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> &lt; 0.01). The results suggest that the DEXA technique has the precision and accuracy necessary to study changes in rat BMD. Furthermore, the technique can be used quickly and noninvasively to detect a bone loss following ovariectomy in the rat, and the distal femur may be an optimal site for detecting such a bone loss. </span></div>