Misinterpretation of osteodensitometry with high bone density: BMD Z > or = + 2.5 is not "normal"

Osteodensitometry is increasingly used to identify low bone density resulting from osteoporosis. The universally accepted World Health Organization (WHO) criteria for assessing bone mineral density (BMD) contrasts individual T-scores to peak BMD in healthy adult control populations. In this scheme, "osteoporosis" refers arbitrarily to T-values below -2.5, "osteopenia" to values between -1.0 and -2.5, and "normal" to values above -1.0. Although individually rare, numerous conditions cause supranormal BMD in children and adults. Increasingly, elevated BMD is detected by osteodensitometry, especially dual-energy X-ray absorptiometry. Illustrated here, the absence of upper limits for BMD in the WHO criteria jeopardizes recognition of high-BMD disease for all age groups. This oversight requires correction using Z-scores.