Bone Density Scan (DEXA)

What it is

Bone thinning gives no warning. There is no ache that precedes it and nothing to feel, which is why osteoporosis is usually described as silent and why the first sign is often a fracture from a fall that should not have broken anything. A DEXA scan is the way to know beforehand. It passes two X-ray beams of different energies through the body; bone and soft tissue absorb the two differently, and subtracting one from the other leaves a measurement of the mineral in the bone alone.

The result is not reported as a raw number but as a comparison — how your density compares with that of a healthy young adult, and separately with others of your own age. This code is for the axial skeleton: the hip and the lumbar spine. Those sites are scanned because they are where fractures do the most damage and because density measured there predicts hip fracture risk better than density measured at a wrist or heel. The small portable machines that scan a finger, forearm or heel are a different, cheaper code and are not interchangeable with this one.

Why it is done

• To diagnose osteoporosis or lower-than-normal bone density before a fracture happens
• To estimate the risk of a future fracture
• To establish a baseline and then track whether density is falling over time
• To monitor bone during treatment that is known to affect it, such as long-term steroids or certain cancer therapies
• To assess someone who has broken a bone from a minor fall, where the fracture itself raises the question
• To decide whether treatment for bone loss is warranted, and later whether it is working

What to expect

There is no injection and no enclosed tube. You lie on a padded open table, fully clothed as long as the clothing has no zips, buckles or metal buttons over the areas being scanned. Your legs are usually rested on a padded block to flatten the lower back, and your foot may be strapped to rotate the hip into position. An arm passes slowly above you. The whole thing takes roughly ten to twenty minutes and you feel nothing. The radiation dose is a small fraction of a standard chest X-ray. Recent barium studies or contrast injections can interfere with the images, so those are asked about when booking.

Questions worth asking

• Confirm the order is for a central hip-and-spine scan rather than a peripheral one. They are separate codes, they are priced very differently, and the results are not comparable.
• If this is a follow-up scan, having it on the same machine at the same facility makes the comparison meaningful. Ask whether that is where it is booked — a cheaper scan elsewhere may not be usable for tracking change.
• Ask whether the radiologist's interpretation is billed separately from the scan.
• Many plans treat bone density scanning as preventive under certain circumstances and diagnostic under others, which changes what you owe. Ask the ordering office which diagnosis code is going on the claim.
• Ask the facility for its self-pay price. DEXA is one of the lower-cost imaging studies, and the cash price is sometimes below a typical imaging copay.