Osteoporosis: NHANES data favored for T score determination

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  • In diagnosing osteopenia and osteoporosis, bone mineral density (BMD) from dual-energy X-ray absorptiometry (DXA) remains the standard; but interpretation of BMD values is affected by choice of reference populations, and BMD is not the only known fragility fracture risk.

Why this matters

  • Small changes in T scores or Z scores may affect treatment recommendations.

Study design

  • A review of the use of DXA results in the diagnosis of low bone density and fracture risk.
  • Funding: None.

Key results

  • As BMD declines with age, the WHO-recommended use of a young population reference for T scores, instead of an age-matched reference (Z scores), dictates that incidence of osteoporosis and osteopenia will greatly increase with age.
  • WHO recommends NHANES reference population for hip BMD and manufacturer databases for spine BMD.
  • BMD values more than 1 SD below the healthy young female reference population define osteopenia and those 2.5 SDs below define osteoporosis.
  • Additional factors contribute to fracture risk with aging, which has led to the more recent development of risk gauges, such as FRAX, that include BMD as one among several factors to use in fracture risk estimation.


  • Additional relevant bone parameters are not included in fracture risk measures.