The controversy of bone density testing in patients already taking osteoporosis medication
The American Medical Association and other reputable medical organizations have determined that repeat bone density testing (DXA scans) is NOT indicated in monitoring osteoporosis treatment or prevention on a routine basis. It is scientifically premature to measure bone density as a way of monitoring the effectiveness of osteoporosis drugs. Doctors simply do not know how to use these repeat bone density measurements during therapy. A few of the most important reasons are:
Bone density changes so slowly with treatment that the changes are smaller than the measurement error of the machine. In other words, repeat DXA scans cannot distinguish between a real increase in bone density due to treatment or a mere variation in measurement from the machine itself.
The real goal of osteoporosis treatment is to decrease future bone fractures. There is no good correlation between increases in bone density with decreases in fracture risks with treatment. For example, alendronate has been shown to decrease fracture risk by 50%, but only to increase bone density by a few percent. In fact, most of the fracture reduction with raloxifene is not explained by raloxifene's effects on bone mineral density.
One density measurement taken during treatment will not help the doctor plan or modify treatment. For example, even if the DXA scan shows continued deterioration in bone density during treatment, there is not yet research data demonstrating that changing a drug, combining medications, or doubling medication doses will be safe and helpful in decreasing the future risk of fractures.
An important note: even if bone density deteriorates during treatment, it is quite likely that the patient would have lost even more bone density without treatment.
Recent research has shown that women who lose bone density after the first year of menopausal hormone therapy will gain bone density in the next two years, whereas women who gain in the first year will tend to lose density in the next two years of therapy. Therefore, bone density during treatment naturally fluctuates and this may not be relevant to the fracture protection of the medication.
For all of these reasons, as surprising as it may sound to many people (and even some doctors), rechecking bone density is not at all like checking blood pressure during treatment of high blood pressure. Routine bone density testing during treatment is unlikely to be helpful. In the future, however, if ongoing research brings new technology or new therapies, testing decisions will clearly change.
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