The cut-off point of dual energy X-ray and laser (DXL) of calcaneus osteoporosis diagnosis in postmenopausal women

Background: Dual X-Ray Absorptiometry (DXA) is a method which can extensively be used for bone mineral densitometry (BMD). Another more recent method is DXL, which associate with dual X ray absorptiometry, assisted by laser measure heel thickness. In this study the cut off points for DXL of calcaneus in the diagnosis of osteoporosis in different bone regions in postmenopausal women had been determined. Materials and Methods: In 268 postmenopausal women, BMD of the spinal and femoral regions was measured by DXA, and the value for the calcaneous was measured by DXL. The agreement of the two methods in the diagnosis of osteoporosis and optimal cut-off point for DXL in defining osteoporosis was obtained. What obtained was the agreement of the two methods in the diagnosis of osteoporosis, as well as the optimal cut-off point for DXL in defining osteoporosis. Results: DXA showed osteoporosis in 40.7 of cases with 35.2 in L2-L4, 16.2 in the femoral neck, and 11.7 for the femoral total region. The DXL found osteoporosis, considering -2.5 SD as a threshold, in 26.1 of cases. Agreement of the two methods in the diagnosis of osteoporosis (Kappa score) was 0.443 for the lumbar region, 0.464 for the neck, and, 0.421 for total femur regions (all P values were significant). Using Receiver Operating Characteristic (ROC ) curves, it was found that a T-score of -2.1, -2.6 and -2.4 as the optimal cut-off point of DXL in the diagnosis of osteoporosis in the lumbar spine, the neck and total region of femur, respectively. Conclusion: The results of this study sh owed a moderate agreement between the two methods in the diagnosis of osteoporosis. It seems that the DXL cannot be used as a substitute for the DXA method, but it can be used as a screening method to find (to diagnose) osteoporosis