What Is a DEXA Scan and What Does It Measure?
Dual-energy X-ray absorptiometry, or DEXA, is the gold standard for measuring bone mineral density (BMD). This non-invasive, low-radiation imaging test precisely quantifies the mineral content in bones, typically at the hips, spine, and occasionally the forearm. The data helps doctors understand bone strength and assess a patient's risk of fracture due to osteoporosis or osteopenia, a precursor to osteoporosis.
Unlike traditional X-rays, which show bone shape, DEXA measures density. The results are provided as two scores:
- T-score: This compares your bone density to that of a healthy young adult of your same gender. A score of -1.0 and above is considered normal. A score between -1.0 and -2.5 indicates osteopenia, while a score of -2.5 or lower indicates osteoporosis.
- Z-score: This score compares your bone density to that of other people in your same age group and demographic. A low Z-score suggests that factors other than normal aging may be contributing to bone loss.
Why a Rheumatologist Orders a DEXA Scan
Rheumatologists are specialists in diseases affecting the joints, muscles, and bones. Their expertise extends to many systemic inflammatory and autoimmune conditions that directly impact bone health. There are several key reasons a rheumatologist may order a DEXA scan:
- Inflammatory Arthritis: Conditions like rheumatoid arthritis (RA) and psoriatic arthritis cause systemic inflammation, which can contribute to bone loss. This bone loss, in turn, increases the risk of osteoporosis and fractures. Monitoring bone density is a standard part of managing these diseases.
- Glucocorticoid (Steroid) Use: Long-term use of corticosteroids, such as prednisone, is a well-known risk factor for drug-induced osteoporosis. Rheumatologists frequently prescribe these medications to control inflammation in autoimmune diseases. Regular DEXA scans are vital for monitoring bone density and mitigating this risk.
- Systemic Lupus Erythematosus (SLE): Patients with lupus are at an increased risk of bone density loss due to a combination of disease activity, corticosteroid use, vitamin D deficiency (often due to sun avoidance), and physical inactivity. A DEXA scan helps assess this multi-factorial risk.
- Ankylosing Spondylitis (AS): Although AS primarily involves spinal inflammation and new bone formation, patients can still develop osteoporosis, particularly in the hips and peripheral skeleton. DEXA scans are important for accurate assessment, especially since spinal overgrowth can artificially inflate lumbar BMD readings.
- Fracture Risk Assessment: The World Health Organization's FRAX tool uses DEXA data to estimate a patient's 10-year fracture risk. Rheumatologists use this information, along with other clinical risk factors, to determine if preventive or therapeutic treatment is needed.
Rheumatologist vs. Other Specialists for Bone Health
Bone health can be managed by several types of specialists. While a primary care physician (PCP) can initiate the process, the root cause of bone loss often determines which specialist is best equipped to manage the condition. Both rheumatologists and endocrinologists have significant expertise in osteoporosis.
| Feature | Rheumatologist | Endocrinologist | Primary Care Physician (PCP) |
|---|---|---|---|
| Focus | Musculoskeletal and autoimmune diseases. | Hormonal and metabolic disorders. | General health and preventative care. |
| Best for... | Osteoporosis linked to inflammatory diseases (e.g., RA, SLE) or long-term steroid use. | Osteoporosis linked to hormonal imbalances (e.g., menopause, hyperparathyroidism). | Initial screening and baseline DEXA scans. |
| DEXA Orders | Frequently orders DEXA scans for at-risk patients. | Often orders DEXA scans, especially for hormone-related issues. | Can order initial DEXA scans and refer to specialists. |
| Common Treatments | Prescribes bone-specific medications like bisphosphonates and can monitor disease-specific factors contributing to bone loss. | Manages hormone-based treatments and related conditions that affect bone density. | Oversees general bone health plan, supplements, and referrals. |
The DEXA Scan Process: From Order to Results
Knowing what to expect can help ease any anxiety about the procedure. The process is straightforward and typically takes about 20-30 minutes.
Preparing for Your Scan
- What to Wear: Wear loose, comfortable clothing without metal zippers, buttons, or belts. You may be asked to remove jewelry.
- Supplements: Stop taking calcium supplements or multivitamins containing calcium for 24 hours before your appointment.
- Contrast Agents: Inform your provider if you have recently had a CT scan with contrast or a barium study, as you may need to wait at least 7-10 days.
- Other Medications: Take other medications as usual unless instructed otherwise by your doctor.
The Procedure
- You will lie on a padded table, and the technologist will position your body, often using foam blocks to support your legs.
- An imaging arm will pass slowly over your body to capture images of your spine and hip.
- You will need to lie very still for a few moments, and may be asked to hold your breath briefly to ensure a clear image.
Interpreting Your Results
After the scan, a radiologist or rheumatologist will analyze the images and send the results to your ordering physician. Your doctor will discuss the T-score and Z-score with you. Based on these results and other risk factors, they will determine if you have normal bone density, osteopenia, or osteoporosis and recommend the appropriate course of action, which could include lifestyle adjustments, supplements, or medication.
Conclusion
In summary, the answer to the question "Can a rheumatologist order a DEXA scan?" is a definitive yes. As experts in musculoskeletal diseases and systemic inflammation, rheumatologists are uniquely qualified to utilize DEXA scans for the diagnosis and management of osteoporosis, especially in patients with complex autoimmune conditions or those on long-term steroid therapy. This proactive approach to monitoring bone health is a critical component of care that can significantly reduce the risk of debilitating fractures and improve long-term outcomes for those living with these chronic conditions. For more information on bone health, you can visit the National Osteoporosis Foundation website, an authoritative resource on the topic.
Visit the Bone Health and Osteoporosis Foundation for more information on bone health.
Frequently Asked Questions
Q: Can a DEXA scan diagnose arthritis?
A: No, a DEXA scan is not designed to diagnose arthritis directly. It measures bone mineral density to assess bone strength. However, it can provide insight into bone loss or structural changes that may be associated with inflammatory arthritis.
Q: Is a DEXA scan painful?
A: No, a DEXA scan is a painless and non-invasive procedure. You will simply lie on a padded table while the scanner moves above you.
Q: How long does a DEXA scan take?
A: The scan itself is quite quick, typically taking only 15 to 30 minutes, depending on the machine and the areas being scanned.
Q: Do I need a referral to get a DEXA scan?
A: Yes, a DEXA scan is a diagnostic test that requires a referral from a healthcare professional, such as a rheumatologist, endocrinologist, or primary care physician.
Q: How often should I get a DEXA scan?
A: The frequency of DEXA scans depends on your bone density results and risk factors. For high-risk individuals or those with osteoporosis, a scan every 1-2 years is often recommended. For those with normal density, scans can be less frequent.
Q: Is a DEXA scan safe?
A: Yes, DEXA scans use a very low dose of radiation, significantly less than a standard chest X-ray. The benefits of early diagnosis and fracture prevention far outweigh the minimal risk of radiation exposure.
Q: Who else can order a DEXA scan?
A: Besides rheumatologists, other doctors such as endocrinologists, gynecologists, and primary care physicians can order a DEXA scan. The best specialist depends on the underlying cause of your bone health concerns.
