A bone density test, or DEXA (Dual-Energy X-ray Absorptiometry) scan, uses low-dose X-rays to measure the mineral content in your bones. This measurement indicates the density or strength of your bones. It helps identify conditions that weaken bones and increase the risk of fractures.
Importance of Bone Density Testing
Bone density testing detects conditions such as osteopenia (low bone mass) and osteoporosis (weak and brittle bones, making them more susceptible to fractures). These conditions often progress without noticeable symptoms until a fracture occurs, making early detection important. Identifying decreased bone density at an early stage allows for timely interventions, which can help prevent fractures and manage bone loss.
When Initial Testing is Recommended
Initial bone density testing is based on age and specific risk factors. Women aged 65 and older and men aged 70 and older are generally recommended for an initial bone density test. However, earlier testing may be advised for individuals with certain risk factors, regardless of age, including a history of fragility fractures after age 50.
Specific medical conditions can also warrant earlier screening, such as rheumatoid arthritis, celiac disease, type 1 diabetes, liver disease, kidney disease, and hyperparathyroidism. Long-term use of certain medications, including corticosteroids, some anti-seizure drugs, and high-dose thyroid replacement drugs, can interfere with bone health and require earlier testing. Other considerations include low body weight, a family history of osteoporosis, or significant height loss.
How Often to Get Re-Tested
The frequency of follow-up bone density tests depends on initial results and ongoing risk factors. For those with normal bone density (a T-score above -1.0) and no significant risk factors, repeat testing every two years provides adequate monitoring. Some research suggests that women with normal bone density or mild osteopenia may not require retesting for 10 to 15 years.
Individuals diagnosed with osteopenia (a T-score between -1.0 and -2.5) require closer monitoring. For moderate osteopenia, retesting is recommended every three to five years, while advanced osteopenia may warrant annual testing. The interval can vary, with common recommendations ranging from every one to two years, especially if the T-score is close to the osteoporosis threshold or if other risk factors are present.
Patients diagnosed with osteoporosis (a T-score of -2.5 or lower) require more frequent monitoring. Annual monitoring is common, particularly if they are receiving treatment. This helps healthcare providers track the effectiveness of medications and make necessary adjustments to the treatment plan. While some medical groups suggest that repeat testing may not be necessary in the first three years of treatment, other organizations still support annual or biennial testing to assess treatment response.
Interpreting Test Outcomes
The primary result of a bone density test is presented as a T-score, which compares your bone mineral density to that of a healthy young adult of the same gender. A T-score of -1.0 or above indicates normal bone density. A T-score between -1.0 and -2.5 signifies low bone mass, known as osteopenia. A T-score of -2.5 or lower indicates osteoporosis.
These T-scores are instrumental in diagnosing bone health conditions and assessing an individual’s risk of future fractures. Alongside the T-score, a Z-score may be provided, which compares your bone density to that of people your own age, gender, and size. An unusually low or high Z-score can suggest that factors beyond normal aging are influencing bone density, prompting further investigation. A healthcare provider interprets these results in conjunction with other clinical factors to determine the most appropriate course of action, including the frequency of future bone density tests and any necessary treatment.