Question: How are X-rays and bone mineral density tests used to diagnose rheumatoid arthritis?
Answer: X-rays and bone mineral density tests are used for different purposes in rheumatoid arthritis. X-rays can be very helpful in identifying certain changes to the joints that are very specific for rheumatoid arthritis. So when we think about arthritis, we're really talking about changes in joints.
There are a lot of reasons people can get arthritis, a lot of different types of arthritis. On X-ray, the changes that occur with rheumatoid arthritis can be very specific and different than the changes that occur with other sorts of arthritis like osteoarthritis, for example, which is a degenerative condition or wear-and-tear. So X-rays can be used to help identify who has rheumatoid arthritis as opposed to some other type of arthritis.
They may not change early in the course of disease. And so sometimes early, when we hope to actually identify the patients with rheumatoid arthritis and begin their therapy, X-rays may be relatively normal. In that situation, X-rays can be helpful to follow the course of treatment, to be sure that they don't begin to change, which may tell us that the treatment we're using isn't adequate and needs to be more aggressive.
Bone marrow density tests tell us something very different. Bone mineral density tests tell us the strength of the bones. When bones become less strong in a situation like osteoporosis for instance, they're more prone to fracture and to damage. People with rheumatoid arthritis are actually more likely to get osteoporosis and weak bones than people who don't have rheumatoid arthritis, though it's not necessarily a specific feature of the disease itself. Nevertheless if we're following or treating a patient with rheumatoid arthritis, we do watch the bone mineral density test because if indeed the bones aren't as strong as they should be, there are specific treatments that we can use to improve that situation and prevent future fractures or future problems.