Discrepant areal and volumetric bone density measurements in a young woman with idiopathic low bone mineral density

Does Bone Mineral Apparent Density Facilitate Accurate Identification of Osteoporosis in the Short Postmenopausal Women?

OBJECTIVE

Height is one of the most important aspects affecting the areal bone mineral density (BMD). There are several height adjustments in children but none in widespread use for adults. This is specifically a problem in ethnic groups where mean height is substantially lower. We hypothesized that height adjustment of areal BMD would reduce the misclassification in short individuals.

MATERIALS AND METHODS

This is a retrospective study involving 373 postmenopausal women. Their records were reviewed and bone mineral apparent density (BMAD) were calculated. Areal BMD T-scores and BMAD T-scores were then compared.

RESULTS

The mean height of the cohort was 154.4 cm. There were 47 women who were defined as short (≤147 cm). In short women, BMAD neither showed improvement nor decrement in T-scores, and BMAD T-scores predicted more number of osteoporosis than BMD T-scores. When divided into height ranges, taller women (>160 cm) showed worsening of BMAD T-scores as compared to BMD T-scores (Chi-square test for trend P < 0.001). Hence, BMAD might actually "correct" for larger bone and not shorter bones.

CONCLUSION

BMAD was not found to be a suitable alternative in short postmenopausal women to accurately determine whether the low bone density in them is because of dual-energy X-ray absorptiometry artifact or whether they truly have a low density.