Discordance in DXA Male Reference Ranges

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Previous studies have reported discordance in female lumbar spine and proximal femur dual-energy X-ray absorptiometry (DXA) reference ranges. Although the NHANES III reference range is recommended for the proximal femur in males and females, there are no published data in men on the concordance or otherwise of the different manufacturer-specific lumbar spine bone mineral density (BMD) reference ranges. Potentially, the use of different reference populations by different manufacturers could result in inconsistencies in the diagnosis of osteopenia or osteoporosis. We compared lumbar spine BMD, as well as T-scores and Z-scores, in 45 men scanned using Lunar DPXL and Norland Excel densitometers. The BMD measured by the two instruments was highly correlated (lumbar spine: r = 0.99, p < 0.0001). However, the two instruments assigned significantly different BMD T-scores (standard deviations from the young reference population). These differences relate primarily to the different standard deviations employed in the calculations. There were also significant differences when BMD was expressed with respect to age-matched values (Z-scores). This study shows that in men, as previously demonstrated in women, two commonly used DXA instruments provide comparable lumbar spine standardized BMD, but there are significant differences in derived T-scores because of differences in the manufacturer-specific reference ranges. Standardization of lumbar spine reference ranges in men should be a high priority.

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