Least Significant Change
Also called: LSC
What it means
Least Significant Change (LSC) is the smallest change in a DEXA scan result that's big enough to count as real, rather than just normal machine error.
Knowing your facility's LSC helps you avoid false alarms or false reassurance when comparing your own bone scans over time.
Least Significant Change, or LSC, is the smallest change in bone density that a DEXA machine can reliably tell apart from its own measurement error. Every scanner has some built-in variability, so a small shift in your numbers between two scans isn't automatically a real change in your bones. It's typically around 3 to 5 percent at the spine, and a bit more at the hip, though this varies by facility.
This matters because it changes how you should read your own results. If your bone density moved by something small, like 1.5 percent, the honest read is usually 'no detectable change' rather than concluding you're losing bone or that something is working. Knowing your facility's LSC helps you and your physician tell the difference between real trends and normal scan noise.
In practice, this means two things are worth doing: get rescanned on the same machine at the same facility whenever possible, since switching machines adds error instead of reducing it, and avoid rescanning too often. For most people, waiting 12 to 24 months gives enough time for a real change to show up above the noise. Asking your facility for their specific LSC is a useful question to add to your own records.
How sure is this?
Graded Strong Clinical Evidence: Supported by multiple well-designed clinical studies in humans. Read each study with its grade in mind. One study is a piece of the picture, not the whole of it.
Where the Academy teaches it
This page is the short version. The lessons teach it in full, with the context around it and a quiz to lock it in.
Questions people ask about this
A T-score compares your bone density to that of a healthy young adult, measured in standard deviations: -1.0 and above is normal, -1.0 to -2.5 is osteopenia, and -2.5 or below is osteoporosis. But it's just one snapshot of density — it doesn't capture bone quality, your fall risk, or your overall fracture probability, so it's worth tracking several other things alongside it and discussing them with your physician.
Read the full answer →A DEXA scan uses a low dose of X-ray to measure bone mineral density at the hip and spine, and it's the long-established standard that generates your T-score. A REMS scan uses ultrasound instead of radiation to assess the same areas, comparing the echo signal to reference models to produce its own T-score (not directly interchangeable with a DEXA T-score) plus a separate "fragility score" reflecting tissue quality. REMS is newer, has less long-term data, and is best used alongside DEXA rather than replacing it, especially if you already have a DEXA history.
Read the full answer →For most people, the honest answer is every 1 to 2 years. DEXA machines have a built-in measurement error, and most facilities can't reliably detect a real change in bone density sooner than that — a small shift of 1-2% on your scan often just reflects machine noise, not actual bone loss or gain. Your physician can tell you the right interval for your specific situation.
Read the full answer →Related words
A DEXA scan is a low-radiation X-ray test that measures how much mineral is in your hip and spine bones, giving you…
A T-score shows how your bone density compares to a healthy young adult, measured in standard deviations, and it's…
A Z-score compares your bone density to other people your own age and sex, which matters most for younger adults,…
Bone mineral density (BMD) measures how much mineral is packed into your bones, usually estimated with a DEXA scan,…
Trabecular Bone Score (TBS) is a measurement taken from your spine DEXA image that estimates how well-connected your…
Education only, not medical advice. Decisions about tests, medications and treatment belong with your own doctor. OsteoStrong does not diagnose, treat or cure any disease.
