DISCRIMINATION OF TOTAL-BODY BONE-MINERAL DENSITY MEASURED BY DEXA INVERTEBRAL OSTEOPOROSIS

The assessment of bone mineral density (BMD) is the usual study to det ect patients at risk for developing osteoporosis, The aim of this stud y was to compare the discriminative ability of total body BMD and its different subregions with the more usual measurements of BMD of the lu mbar spine and femoral neck in women with osteoporotic fractures of th e spine. The BMD was determined in 61 osteoporotic (at least one verte bral wedge fracture visible in the lateral X-ray film of the thoracic or lumbar spine) and 61 age-matched control women. Measurements were m ade by dual X-ray absortiometry (DXA) with a total body scanner. The B MD of the osteoporotic women was significantly lower at all skeletal a reas compared with control (P < 0.001). The diminution was less pronou nced but still significant at the arms (P < 0.05). The areas with the largest Z score in the osteoporotic group were antero-posterior lumbar spine (-1.78), femoral neck(-1.71), legs (-1.67), and total body (-1. 59). There was no significant difference among the Z scores of the fou r above-mentioned measurements. The Z score of the arms (- 0.79), spin e (- 1.12), and head (- 1.29) were significantly lower than the Z scor e of the total body. The Z score of the pelvis was lower than the Z sc ore of the total body but the difference only approached statistical s ignificance (0.05 > P < 0.1), The Z score of the anteroposterior lumba r spine (-1.78) was compared with the Z score of the total (- 1.12) lu mbar (-0.93) and thoracic (-1.38) spine obtained as subregions of the total body. The best differentiation of the two populations was found by measuring the antero-posterior lumbar spine directly (P < 0.01-P < 0.001), In conclusion, the diagnostic differentiation of the total bod y BMD is similar to that of the anteroposterior lumbar spine and proxi mal femur measurements. In addition, the measurement of the total body BMD has a lower error and enables simultaneous evaluation of the diff erent subregions of the skeleton as well as the body composition. The BMD of the spine as a subregion of the total body cannot replace the d irect evaluation of the anteroposterior lumbar spine.