Understanding Your Bone Density Results

What is a T-score?

A T-score compares your bone mineral density against the average for a healthy young adult at peak bone mass. It is expressed in standard deviations, so a T-score of −1.0 means your density is one standard deviation below that reference point.

The World Health Organization's diagnostic thresholds, which clinicians work from, are: −1.0 and above is normal; between −1.0 and −2.5 is low bone mass, commonly called osteopenia; and −2.5 or below meets the criterion for osteoporosis.

Those cut-offs are categories on a continuum, not cliffs. A T-score of −2.4 and one of −2.6 describe almost identical bone, even though only one of them carries the word osteoporosis.

What is a Z-score, and why do you get both?

A Z-score compares you against people of your own age, sex and body size rather than against a young adult. It answers a different question: not "how far are you from peak?" but "how far are you from typical for someone like you?"

That distinction matters most at the two ends of the age range. For premenopausal women, men under 50, and children, Z-score is the appropriate comparison and T-score is not used diagnostically. A markedly low Z-score in anyone is a prompt to ask whether something other than ageing is driving the bone loss.

Why the hip and spine specifically?

The Desert Dexa Osteoporosis Screening scan measures the lumbar spine and both femurs. Those are the sites used because they are where fragility fractures do the most damage and where the diagnostic thresholds were established. You get BMD, a T-score and a Z-score for the left femur, the right femur and the spine.

Sites can disagree with each other, which is one reason a single number from a heel or wrist screening device is not equivalent. When they disagree, the lower value generally drives the clinical picture.

What the radiologist adds

Your Osteoporosis Screening report is not a printout of numbers. An independent board-certified radiologist interprets the scan and writes it up, flagging osteoporosis or osteopenia indications where they apply, and noting anything about the images that affects how the numbers should be read.

That last part matters more than it sounds. Spinal degeneration, previous fractures, scoliosis and hardware can all raise a measured density value without the underlying bone being stronger. Reading a spine number without accounting for that is how someone gets falsely reassured.

This report reaches you within about 3 days, and it is written to be handed to your physician.

What a score does and does not tell you

Bone density is one input into fracture risk, not the whole of it. Age, previous fracture history, family history, smoking, long-term steroid use and several medical conditions all contribute, which is why clinicians combine a T-score with those factors rather than treating the number in isolation.

The practical consequence: a T-score in the osteopenia range does not automatically mean treatment, and a normal T-score does not automatically mean no risk. Those are conversations for your physician, working from the report.

What happens next

Take the report to your doctor. Depending on what it says and what else is in your history, the conversation is usually about whether to treat, what to change, and when to measure again. Follow-up timing is a clinical decision they make from your result and your risk factors — it is not something we set.

What we can say is that a comparison is only meaningful if the scans are alike. Our scanners are fixed-site clinical systems on a daily calibration schedule, so a repeat scan at Desert Dexa measures change in you rather than difference between machines.

Do I need a referral for this scan?

Not one you have to go and get. Most providers ask you to bring a physician order for bone densitometry; at Desert Dexa our own physician orders the scan, so you can book the Osteoporosis Screening directly. The resulting radiologist report is exactly what your doctor would have ordered.

This article is for general information and is not medical advice. DEXA results should be interpreted alongside your own clinical history. Talk to your physician about decisions relating to your health.

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