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What does “osteoporosis -2.5” mean? To answer that question, we start with bone density scans, sometimes referred to as bone densitometry or dual-energy x-ray absorptiometry (DEXA, also written as DXA). Such scans have become an increasingly popular testing modality as more than 10 million adults in the United States alone suffer from osteoporosis and more than 43 million adults have low bone mass (osteopenia), putting them at risk of osteoporosis.
People with osteoporosis have weak, brittle bones for a variety of reasons, including sex hormone deficiencies or changes; overactive thyroid glands; dietary insufficiencies (particularly calcium and vitamin D); prolonged use of medications such as steroids; and lifestyle factors such as excessive alcohol consumption.
The major concern with osteoporosis is the significantly increased risk of fracture. Statistics demonstrate that approximately 1.5 million people in the U.S. suffer a fracture each year because of bone disease.
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Reasons for a Bone Density Scan
Your healthcare provider may order a bone density scan for you if you’re at risk for osteoporosis or osteopenia for one of many reasons, including:
- Age: Your risk of osteoporosis increases with age. This is particularly true for women whose risk significantly increases after they go through menopause.
- Body frame: Thin men and women generally have less bone mass.
- Family history: Having had a parent or sibling with osteoporosis greatly increases your risk, particularly if they suffered a fracture.
- Hormonal diseases: Overactive thyroid (or hyperthyroidism), parathyroid, and adrenal glands can increase your risk of osteoporosis because of the elevated levels of hormones they produce.
- Medications: Individuals who have taken prolonged courses of steroids, aluminum-containing antacids, some chemotherapy drugs, or some seizure medications (such as Dilantin) are at increased risk of osteoporosis.
- Eating disorder: People suffering from anorexia who have a long history of insufficient calorie and, therefore, calcium and protein intake are more likely to develop osteoporosis. Many people suffering from anorexia will also develop sex hormone deficiencies, further increasing their risk.
- Unexplained fracture: Having suffered a fracture after only very mild trauma or having had evidence of a fracture you were not aware of revealed on another test will raise your healthcare provider’s suspicion of osteoporosis.
What Is the Actual Test Like?
A bone density scan or DXA is generally a very easy, painless outpatient procedure that does not require anesthesia and takes only 10 to 30 minutes. The primary type of DXA used to evaluate osteoporosis is called a “central DXA” because it measures bone density in the hip and lower spine, which are in, roughly, the “center” of the body.
You may have a central DXA performed in a radiologist’s office or in a rheumatologist or endocrinologist’s office. How does it work? You’ll be instructed to lie on a long, flat table that has an x-ray generator underneath and an imaging arm suspended overhead. You’ll likely be positioned in very specific ways to maximize visibility of your hip and spine. The arm of the DXA will pass slowly overhead, taking images of the bone as the x-ray generator sends low-dose beams of x-ray from underneath.
Some people may also have a test called a lateral vertebral assessment (LVA) performed at the same time. This is a very brief test used to assess fractures of the spine and is generally done in people who have experienced a loss of height or unexplained back pain.
What Does “Osteoporosis -2.5” Mean? Interpreting Your T-Score Results
When you receive your bone density scan or DXA results, they’ll be in the form of two scores: a T-score and a Z-score.
- T-Score: The T-score is the result most people refer to when discussing their DXA results. It compares your bone mineral density, no matter what your age, with that of a young adult of your gender who has peak bone mass. The value of your score determines your diagnosis:
- A T-score of -1 and above is normal.
- A T-score between -1 and -2.5 is defined as osteopenia or low bone mass.
- A T-score of -2.5 or below is defined as osteoporosis.
- Z-Score: The Z-score compares your bone mineral density with other people your age of the same size and gender. Because most older adults have some bone mineral loss, Z scores are most helpful in children, teenagers, and young women still menstruating.
- A Z-score above -2.0 is considered to be within the expected range for age.
- A Z-score below -2.0 is considered to be below the expected range for age.
Your healthcare provider will discuss your results with you and may initiate treatment either with lifestyle modifications or medication if your results indicate you have significant osteopenia or if you have osteoporosis. Follow-up bone scans are performed on a regular basis to assess for further bone loss and to monitor your response to treatment.