Should BMD be used to monitor osteoporosis therapy? (Pro & Con).

YES We know that in populations, treatments for osteoporosis increase bone mineral density, change biochemical markers of bone turnover, and reduce the risk of fractures.

In individual patients, we can't measure changes in the risk of fracture. But it does make sense to consider monitoring something we can measure: biochemical markers of bone turnover and/or changes in bone mineral density (BMD).

There's an appealing utility to BMD measurement. It can be seen as a personalization of an abstract generality, potential motivation for behavioral change, and a useful vehicle for patient-physician interaction. There's an intuitive value in measuring what is being treated. It's an opportunity to convey physician concern.

I recommend monitoring the BMD at the posterior-anterior spine for precise results at a location most responsive to therapy. Try to use the integral measurement for L1 through L4. If the spine cannot be used because of degenerative changes or other factors, use the total hip. Peripheral devices should not be used for monitoring.

Changes in spine BMD after 3 years of treatment, as reported in various studies, suggest that with estrogen and bisphosphonates, at least, you should be able to measure an increase in BMD.

For serial BMD measurements, it's very important to use the same machine and method, measure the same site, be sure the patient's position is the same, and make the same adjustments. Monitor bone density, not the T-score. And in looking at the values, look not only at BMD but also at bone mineral content and area.

I should point out that it's important not to overestimate "change." Small differences are not usually biologically relevant, but are simply due to technical error of the procedure, calculated in centers as "least significant change."