You had a DEXA scan. You got a report back with numbers like T-score -2.1, Z-score -0.8, TBS 1.295, and FRAX 14%. Now you're sitting at home trying to figure out what any of it means before your follow-up appointment. Here's a plain-language breakdown of every number on a Canadian DEXA report.
DEXA stands for Dual-Energy X-ray Absorptiometry. The scanner measures how much X-ray is absorbed by your bones versus your soft tissue at specific sites — typically the lumbar spine (lower back) and hip. The result is a bone mineral density (BMD) measurement in grams per square centimetre (g/cm²).
The raw BMD number doesn't mean much to most patients on its own. So the report converts it into comparative scores — T-scores and Z-scores — and may include additional analyses like TBS and FRAX. Each of these is answering a different question.
For an overview of the scan itself — what to expect, how to get one in Canada, provincial coverage — see the DEXA scan in Canada guide.
The T-score compares your bone density to the average peak bone density of a healthy 30-year-old of the same sex. A T-score of 0 means exactly average for a 30-year-old. A score of -2.0 means your density is 2 standard deviations below that young-adult average.
| T-Score Range | Category | What It Means |
|---|---|---|
| Above -1.0 | Normal | Bone density is within normal range for peak bone mass |
| -1.0 to -2.5 | Osteopenia (low bone mass) | Below average but not osteoporosis; fracture risk is elevated but not high |
| -2.5 or below | Osteoporosis | Significantly below average; WHO diagnostic threshold for osteoporosis |
| -2.5 or below + fragility fracture | Severe osteoporosis | Osteoporosis plus a fracture from minimal trauma |
The WHO T-score threshold of -2.5 for osteoporosis diagnosis comes from a 1994 definition based on femoral neck measurements in white postmenopausal women. The same thresholds are now applied more broadly, though there are ongoing debates about how well they apply across ethnicities and in men.
Your report will show T-scores for the lumbar spine and multiple hip sites. The lowest score at any major site (spine, total hip, or femoral neck) is used for the diagnosis. If your spine shows osteoporosis but your hip doesn't, you still have osteoporosis for diagnostic purposes.
One important caveat: in people over 65, spinal T-scores can be artificially elevated (look better than they are) due to osteophytes — bone spurs from arthritis that add density on the DXA image but don't represent healthy bone. If you have significant lumbar spine arthritis, your hip T-score is usually more clinically meaningful. Ask your doctor about this if your lumbar and hip scores differ substantially.
The Z-score compares your density to the average for someone of your age, sex, and sometimes ethnicity. A Z-score of 0 means you're average for your age. A Z-score of -1.0 means you're below average for your age group — but average for a 30-year-old might look much worse.
For postmenopausal women and men over 50, the T-score is the primary diagnostic metric. The Z-score becomes more important in specific situations:
A Z-score of -2.0 or lower (regardless of age) is a clinical flag. It means your bone loss is greater than expected for your age — which suggests a secondary cause of bone loss that should be investigated: hyperparathyroidism, celiac disease or malabsorption, hyperthyroidism, vitamin D deficiency, excessive alcohol use, steroid use, or other medical conditions.
Concretely: a 70-year-old woman might have a T-score of -3.5 but a Z-score of -1.2 — meaning she has less bone than a 30-year-old (expected) but about average for her age. Another 70-year-old with T-score -3.5 and Z-score -2.5 has much less bone than her peers, and that gap needs explanation.
TBS is the number that generates the most confusion because many patients have never heard of it before receiving their first report that includes it — and it's not obvious what "TBS 1.276" means or why it matters.
BMD measures how much bone you have. TBS measures the quality of that bone's internal microarchitecture. Specifically, it analyses the texture pattern of the lumbar spine DXA image using software (iNsight, by Medimaps Group) to estimate the trabecular — the honeycomb-like internal scaffolding of bone. Denser, more connected trabeculae = stronger bone = higher TBS.
Two people can have the same T-score but very different fracture risk if their TBS differs significantly. Someone with a T-score of -2.3 and TBS of 1.18 (degraded microarchitecture) is at higher fracture risk than someone with the same T-score and TBS of 1.35 (normal microarchitecture).
| TBS Value | Interpretation |
|---|---|
| >1.310 | Normal bone microarchitecture |
| 1.230–1.310 | Partially degraded microarchitecture |
| <1.230 | Degraded microarchitecture — significantly increased fracture risk |
These thresholds come from ESCEO consensus guidelines (PMC4538791). They apply regardless of age and sex.
TBS has been integrated into the FRAX fracture risk calculator. A low TBS increases the FRAX-calculated 10-year fracture probability — sometimes enough to push a borderline patient from "monitor with lifestyle changes" into "discuss medication." Osteoporosis Canada has incorporated TBS-adjusted FRAX into some clinical recommendations.
Not all DEXA machines in Canada have TBS software. If your report doesn't include TBS but you'd like it, ask whether the facility has iNsight software and if it can be run on your existing scan data.
FRAX is the most clinically actionable number on your report — and also the one most patients don't notice. It's the 10-year probability of:
FRAX is calculated by plugging your femoral neck T-score into a model that also accounts for your age, sex, body weight, height, personal fracture history, parental hip fracture history, smoking status, alcohol use (3+ drinks/day), glucocorticoid (prednisone) use, rheumatoid arthritis, and secondary osteoporosis causes. You can run it yourself at the fracture risk calculator.
Canadian guidelines differ from US and UK thresholds. Osteoporosis Canada uses FRAX to guide treatment decisions roughly as follows:
This is why T-score alone doesn't determine treatment in Canada. A 55-year-old with T-score -2.7 and no other risk factors may have a 10-year fracture probability of 12% — below the treatment threshold. A 72-year-old with T-score -2.2, a prior wrist fracture, and a parent who fractured a hip may have a 24% FRAX — well above threshold despite a better T-score.
The actual bone mineral density measurement in grams per square centimetre is the raw data everything else is derived from. It appears on your report as, e.g., "Lumbar Spine BMD: 0.832 g/cm²."
The BMD number by itself isn't very meaningful without context — it's the T-score and Z-score comparisons that give it clinical meaning. But the BMD value is what you track over time on treatment. If your lumbar spine BMD goes from 0.832 to 0.868 g/cm² over two years on alendronate, that's a real improvement.
T-scores move in parallel, but the actual BMD measurement is the most direct way to track treatment response.
No medication needed. Focus on lifestyle: weight-bearing exercise, adequate calcium and vitamin D, no smoking. Retest in 5–10 years depending on risk factors.
Run the FRAX calculator (or ask your doctor for it) to get your 10-year fracture probability. If FRAX is below the treatment threshold, optimize lifestyle: resistance exercise, calcium 1,200 mg/day, vitamin D 800–2,000 IU/day, and retest in 3–5 years. If FRAX crosses the threshold, discuss medication. The T-score alone doesn't answer the question.
Medication is typically indicated. Your doctor should calculate or review your FRAX, assess secondary causes if appropriate (especially if Z-score ≤ -2.0), and discuss treatment options. Don't leave this appointment without a clear plan. If you've already had a fracture, the urgency is higher.
A TBS under 1.23 with a T-score in the osteopenia range can be enough to push FRAX-adjusted fracture risk into treatment range. Ask specifically for TBS-adjusted FRAX if your report includes TBS.
Go in with your report in hand and ask:
If you feel rushed, bring written questions. Canadian GPs typically have 10–15 minutes per appointment; focusing on the two or three questions that matter most will get you further than trying to cover everything.