A Bone to Pick With Osteoporosis Tests

The “gold standard” of testing for osteoporosis (loss of bone density and strength) has long been the DXA scan, and many prescriptions for bone-building medications like Fosamax and Boniva have been made based primarily on DXA findings.

Osteoporosis drugs are unfortunately far from perfect, and often come with significant side-effects, but their use may be justified, given the potential for major fractures and subsequent associated losses of function and health they often cause.

But the justifications for these prescriptions might not be so strong if the tests that led to them were less than totally reliable. And herein lies the problem of the gold standard status of DXA tests.

When you call something “the gold standard” it kind of suggests that it’s the be-all, end-all test. Why would you even consider anything besides a test with such a reputation?

Unfortunately, DXA testing has a rather large limitation: it doesn’t account for bone size and it can’t tell the difference between a small bone that has good density and a large bone with poor density.

This leads to two problems – over-diagnosing osteoporosis and osteopenia in smaller-boned individuals, and under-diagnosing them in people with larger than average bones. This in turn leads to inappropriate treatments.

Now, there are bone density tests that do account for bone size. QCT and BCT both use CT scan technology to assess bone density (QCT) and bone strength (BCT). But these tests are not typically used in the majority of patients, and tend to be applied when a larger-boned patient shows signs of osteoporosis but has normal DXA results.

So, while further investigation is often appropriately applied when a larger individual has a suspected false-negative on DXA, the possibility of a false-positive in a smaller-boned person seems to be largely ignored. This is probably in part due to the fact that smaller-boned individuals do have a higher incidence of fractures, but this is not necessarily due to diminished bone density, as the common assumption seems to be.

Just the fact that the bones are not as thick and that thinner people tend to have less muscle and fat mass to support and cushion the bones during trauma would tend to make them more prone to fractures. These factors can be addressed to some degree with things like resistance exercise, but all too often the default is to prescribe drugs if the DXA findings indicate any loss of bone density.

If the drugs were harmless, this wouldn’t be a problem, but as mentioned earlier, side-effects are common, and may include muscle and joint aches, pain, and swelling, as well as more rare side effects such as osteonecrosis (rapid deterioration of the bone) of the jaw and, ironically, fractures (despite improving bone density, the drugs inhibit the normal turnover of bone making them more brittle in some cases).

This is not to say that you shouldn’t consider osteoporosis drugs if you legitimately have osteoporosis and are at significant risk for fractures in major bones like the hip and spinal vertebrae. Sustaining such fractures can have severe health consequences and although the drugs aren’t perfect, they may be the best option if you have significant loss of bone density.

On the other hand, if you don’t actually have decreased bone density, but simply have a false-positive from the gold-standard DXA test, you likely will be prescribed medication you don’t need, and potentially be subject to side-effects unnecessarily.

With that in mind, my suggestions are as follows:

If you are a thin person and your DXA test has indicated osteoporosis or osteopenia, ask your doctor about getting a confirmation from a bone density test like QCT or BCT that will take your bone size into consideration before considering medication.

If you have a large frame and you’ve suffered fractures that seem unusual for the degree of trauma that caused them, request QCT or BCT if your DXA was normal to make sure your bone density is what it should be.

Although getting adequate calcium, vitamin D, and other bone-building nutrients is important, weight-bearing exercise is probably more important in most cases for maintaining (and possibly improving) bone density and strength. If you have been diagnosed with advanced/severe osteoporosis, and/or have other health issues such as cardiovascular problems, check with your doctor as to what type of exercise is appropriate for you. Otherwise, walking and some type of resistance training are highly recommended.

Try to mitigate what risk factors you can. Avoid smoking and excess alcohol and caffeine consumption. Work with your doctor on keeping hormones like estrogen, progesterone, and testosterone in balance, particularly if you’ve had a hysterectomy and/or have gone into menopause early.

Finally, if you have been diagnosed with severe osteoporosis and/or your osteoporosis is advancing more rapidly than is typical, ask your doctor about being tested for hyperparathyroidism. Not to be confused with the thyroid, the parathyroid glands produce a hormone that pulls calcium from the bones (under normal circumstances, this mechanism maintains necessary levels of calcium in the blood for normal heart and muscle function). If the parathyroid glands become overactive, loss of bone density occurs at an accelerated rate and other problems, such as kidney stones, commonly occur due to elevated calcium in the blood.

It may take a little effort to convince your doctor to take the extra step to go beyond a DXA test, especially since it is widely accepted as the “gold standard.” And while medication may indeed be appropriate in your case, I think it makes sense to confirm that you actually need them as opposed to accepting results from a test that may not be reliable for your body type.

Until next time…

George F. Best, D.C.