Bone Mineral Density: Methinks Thou Dost Test Too Much

Screening for osteoporosis by assessing bone mineral density (BMD) has become an integral part of the care we provide to our older patients. Medicare pays for dual-energy x-ray absorptiometry (DXA) screening every two years or more frequently if the procedure is determined to be medically necessary. Based on my discussions with colleagues, however, striking heterogeneity clearly exists in the frequency with which we obtain BMDs. How frequently do we really need to screen?

In a recent report in the New England Journal of Medicine, the Study of Osteoporotic Fractures Research Group provides clinicians with refreshingly helpful data to inform our practices (N Engl J Med. 2012;366:225-33). In a cohort of 4,957 women two transitions were evaluated: 1) from normal BMD to osteoporosis; and 2) from osteopenia to osteoporosis. The BMD “testing interval” was defined as the estimated time for 10% of women to make the transition to osteoporosis before having a hip or clinical vertebral fracture, with adjustments for estrogen use and clinical factors. Participants were stratified into normal BMD (T score, −1.00 or higher), mild osteopenia (T score −1.01 to −1.49), moderate osteopenia (T score −1.50 to −1.99), and advanced osteopenia (T score −2.00 to −2.49). The estimated BMD testing interval was 16.8 years (95% confidence interval [CI] 11.5 to 24.6) for women with normal BMD, 17.3 years (95% CI 13.9 to 21.5) for women with mild osteopenia, 4.7 years (95% CI, 4.2 to 5.2) for women with moderate osteopenia, and 1.1 years (95% CI, 1.0 to 1.3) for women with advanced osteopenia. Within a given T-score, the transition from osteopenia to osteoporosis was longer for women of younger age, higher BMI, and estrogen use. Table 3 provides an excellent reference tool for tailoring screening intervals for our patients. When the testing interval was redefined for 20% of women to make the transition from osteopenia to osteoporosis, the time estimates were 80% longer.

These findings provide some rationale, evidence-based guidelines upon which we can base our testing intervals. This will help us do our part to avoid breaking the bank in the interest of avoiding breaking a bone.

Dr. Ebbert reported having no relevant conflicts of interest.