Interpretation of lumbar spine densitometry in women with fractures

Abstract

Identification of postmenopausal women at risk of developing osteoporotic fractures is a major clinical problem. In this study the use of projected planar lumbar bone density values for individual fracture risk assessment was questioned. Osteodensitometry (DXA) results from 415 normal women, 62 women with previous vertebral compressions, and 76 women with previous low-energy fractures were analyzed, together with their body size and lumbar vertebral body size variables. The following were found: (1) Lumbar vertebral projected bone mineral areal density (BMD) and bone mineral content (BMC) of normal women correlated with body size variables (p < 0.001). (2) Lumbar vertebral body size variables also correlated with body size variables (p < 0.001). Logistic regression analysis of measured and derived physical variables from women without and with vertebral compression fractures (n = 477) showed: (3) The best compression fracture discriminator, significantly better than BMD, was BMC divided by (Hmax/165 cm)1.5 x (D/4.35 cm)1.5, where Hmax is the body height (cm) at the menopause, and D the mean lumbar vertebral diameter of the three mid-lumbar vertebral bodies (cm). This parameter was termed BMCcorr.. ROC analysis showed: (4) At a BMCcorr. true positive ratio of 80% the corresponding uncorrected BMC or BMD true positive ratio was only 60%. The corresponding false positive ratio was 6%. Lumbar osteodensitometry could not be used to identify women with a history of peripheral low-energy fractures. (5) BMCcorr. did not, unlike BMC and BMD, correlate with body size and vertebral size variables. (6) Likewise, an observed correlation between BMC and lean body mass in a subpopulation of 116 normal women was abolished when BMCcorr. replaced BMC.(ABSTRACT TRUNCATED AT 250 WORDS)

Multiparity and bone mass

“…Hence, by using BMD rather than BMC the influence of body size differences between individuals was diminished, although not abolished. In this study, as in others 3 , there was a significant correlation between BMD and body mass index (BMI) ( P < 0.01).…”

Whole body bone mineral content in healthy children and adolescents

“…We have chosen not to use BMD calculated as BMC/bone area because BMD measured with anterior-posterior osteodensitometry represents a mixture of true density and skeletal size 2023 24 Note that the regression coefficient for log transformed BMC on log transformed bone area may be interpreted as a power for bone area. In the present data, the regression coefficient was highly significantly different from 1, indicating that the use of BMD would only partially adjust for bone area.…”

The Fallacy of BMD: A Critical Review of the Diagnostic Use of Dual X-ray Absorptiometry

“…We have previously shown, using ROC analysis and logistic regression analysis, that when lumbar spine BMC was corrected for bone size and body size, the discriminatory ability of DXA for vertebral fracture was much improved, but that lumbar osteodensitometry could not be used to identify women with a history of peripheral low-energy fractures [43]. It was demonstrated for vertebral fractures that body and bone size correction improved the true positive fraction from 60% to 80% at a 5% false positive fraction.…”