Question
I am a 92 lb 5 ft 59 yr old female on Fosamax for 5 years. My previous bone density test 5 years ago read: spine -2.6 and hips -3.5. My new test read spine -2.3 and my hips -3.8. The radiologist confirmed that the machines since then have been recalibrated so he could not make a good comarison. I did have the test done at another facility in the same hospital system. Could that mean that my hips might not have changed but the new calibrations have higher standards? Also, is it common to improve in your spine and get worse in your hips while on Fosamax. Does Fosamax generally work better on the spine than hips?
Answer
You need a specialist in osteoporosis to review your bone density studies (DXA scans) carefully. The DXA machines from different manufactures vary in the method they use to calculate bone density. Thus, if the models of the machines are different, you may not be able to compare values. A formula can be used to try to compare values from different machines. The values you quoted may not be that different. Also remember that the values for the spine are averages usually of the lumbar vertebrae L1-L4, thus it is important to look at the values for each vertebrae. A fracture in one vertebrae can actually raise the average value. It is important that DXA scan provide a detailed report to your doctor and not just one or 2 numbers.
