If you have osteoporosis, you can have a DXA bone density test once a year for monitoring treatment. Most people, even doctors are confused about this. They confused the Medicare rules governing bone density testing to screen people for osteoporosis, which is allowed every two years with the rules for testing people with the disease on treatment who require monitoring that is allowed one annually. All payors reimburse monitoring treatment with DXA bone density once every year.
I am a member of the International Society for Clinical Densitometry ISCD and use their guidelines to interpret bone density tests. Visit their site at www.iscd.org for a lot of great information for consumers on osteoporosis. There is information for medical professionals too. The ISCD guidelines consider no significant loss in bone density or a gain in bone density to be a positive response to treatment. Only a significant loss in density is a real loss. When that happens, it is important for your doctor to investigate why that happened. Are you taking your calcium citrate, vitamin D, and medication properly? Has some new medical problem popped up like hyperthyroidism complicating your situation? If the answer is no, then you should discuss changing the medication with your doctor.
Bone Turnover Markers
I use CTX and P1NP as part of my diagnostic evaluation of people with osteoporosis and to monitor their response to therapy. Bone turnover markers are complementary to DXA as a way to monitor your response to treatment. BTM provide information DXA does not and vice versa. The nice thing about BTM is they can be done before 3 months after you start treatment providing us with valuable information 9 months before we would learn anything from the DXA.
We know from their use in osteoporosis studies exactly how these markers respond in people who later on are shown to have positive benefits from the treatment, principally reduced fracture rates. The markers also predict change in bone density and the direction of change. I obtain bone turnover markers when the patient is first seen in consultation then repeat the BTM 3 months after they have begun treatment. This provides great insight into how they are managing the treatment and the treatment’s effect on the bone remodeling system. From the BTM results, I am able to tell the patient what the expected result of her or his therapy will be in the future.
These graphs are from an osteoporosis treatment study in postmenopausal women. The study lasted 12 months and compared parathyroid hormone vs. alendronate vs. parathyroid hormone plus alendronate. The graphs show the affect the three treatment groups had on P1NP, a marker of bone formation and CTX, a marker of bone absorption. Parathyroid hormone is an example of an anabolic osteoporosis therapy. Alendronate is an example of an anti-remodeling osteoporosis therapy. The affect on the bone markers of these agents seen in this study is a classic example of what other agents with similar mechanisms of action can be expected to have in patients treated with them in clinical practice who are monitored during treatment. Black, et. al. New Engl J Med 2003; 349:1207-15