E Michael Lewiecki, MD: When is Osteopenia Osteoporosis?

Rheumatology Network sat down with E Michael Lewiecki, MD, Director at the New Mexico Clinical Research and Osteoporosis Center, to discuss his CCR West presentation “When is Osteopenia Osteoporosis?” We discuss the definition of osteopenia, Lewiecki provides examples of when an initial diagnosis of osteopenia may instead be osteoporosis, and what rheumatologists need to know regarding this differentiation.

E Michael Lewiecki, MD

Rheumatology Network: Can you give me a bit of background on osteopenia?

E Michael Lewiecki, MD: The World Health Organization (WHO) and the International Society for Clinical Densitometry (ISCD) have a definition for osteopenia, which includes a T-score by dual x-ray absorptiometry (DEXA) that's between -1.0 and -2.5. That's the lumbar spine, femoral neck, total hip, or 33% radius if it's measured in a particular group of patients, such as postmenopausal women and men aged 50 and older. That is the official definition. However, there are some situations where people have T-scores within that range and the diagnosis is actually osteoporosis.

I’ll give you 3 examples of that. Example number 1 is when a patient is treated for osteoporosis, they have a T-score of -2.5 or below, in the osteoporosis range, and they get put on medication. Then, a year or 2 later, and they have another bone density test. And this time, the T-score is between -1 and -2.5. So, the report might incorrectly say that the diagnosis is osteopenia based on that T-score. This is an incorrect interpretation of the DEXA, and it might lead to some unfortunate circumstances, such as the patient deciding they don't have osteoporosis anymore and stop taking their drug.

The doctor is then stuck in the middle and may have to stop prescribing that drug. That would be very unfortunate, especially with drugs such as denosumab, which will be followed by a rapid decrease in bone density. It would be like treating somebody for hypertension and when blood pressure is under control with medication saying that the patient no longer has hypertension and stopping the blood pressure medicine. What's going to happen is the blood pressure goes right back up.

Now we think of osteoporosis as a lifelong disease. When you treat a patient for osteoporosis with a T-score that's -2.5 or below and the T-score becomes better, the diagnosis of osteoporosis still continues. A better report, for that second bone density test that showed a T-score that was better than -2.5, might be that the patient has osteoporosis with improvement in bone density with treatment, which means they have an excellent response to therapy and treatment should be continued, provided there's no contraindication.

Example number 2 is if a patient has a T-score between -1 and -2.5 and they have a fracture. The presence of a fracture is consistent with a diagnosis of osteoporosis regardless of T-score. The most common kind of osteoporotic fracture is in the spine. Most people who have spine fractures don't know they have them. So, if you have a bone density test that shows osteopenia, and the patient has had some historical loss of height or unexplained back pain, you might want to get an image of the spine. And if that shows a fracture, even if it was previously unrecognized, the diagnosis would become osteoporosis. Another example is having a hip fracture with bone density that's in the osteopenia rage. In fact, at least half of patients with hip fractures have a T-score that's better than -2.5. Those patients have osteoporosis by virtue of the fact that they've had this fracture.

The third example is with the Fracture Risk Assessment Tool (FRAX). Often, when a patient has osteopenia, we’ll do a FRAX and estimate the 10-year probability of major osteoporotic fracture and the 10-year probability of hip fracture. If those values are high, that is consistent with having osteoporosis and it's an indication for treatment. Some people would make a diagnosis of osteoporosis in a patient with a T-score better than -2.5 if the 10-year probability of major osteoporotic fracture is 20% or greater or the 10-year probability of hip fracture is 3% or greater.

RN: What do rheumatologists need to know about this differentiation?

ML: Regarding FRAX and unrecognized vertebral fractures, these concepts are very helpful in patients on long-term glucocorticoids. Rheumatologists use a lot of these and common fracture in patients on long-term glucocorticoid therapy is in the spine. Sometimes, they're unrecognized. I think rheumatologists need to be vigilant when considering the possibility of patients having spine fractures when they're on prednisone, for example, and consider doing spine imaging, which can be done at the same time as a DEXA studies done with a lateral image of the spine, called vertebral fracture assessment (VFA). And, of course, long-term glucocorticoid therapy is a risk factor for FRAX. If that's included in the FRAX algorithm, they may find that the patients at higher risk of fracture than they previously estimated.