Avoidboneloss.com

For accurate comparison of bone density results, it's best to be retested on the same densitometer. However, this is not always possible because test centers may go out of business or replace an old densitometer with a new one; or patients may move out of town. If you switch from a GE or Norland densitometer to a Hologic densitometer, you can use the following conversion tables to make your DXA results more meaningful because the BMD numeric results will be different on machines by different manufacturers.

The T-scores, however, should be equivalent, except for the those of the femoral neck. Hologic measures the femoral neck at a point closer to the trochanter than GE, and as a result Hologic femoral neck T-scores may be slightly higher than those of GE. Keep in mind that slight differences in measurements may occur even on the same machine, but the newer machines are becoming more and more consistent with their results.

The information below will help you determine if your bone densities went up, down, or stayed the same between tests. The formula for calculating % changes is:

(BMD of current test - BMD of previous test) ÷ BMD of previous test.

The information below is courtesy of Hologic^®.

Converting Lunar and Norland

BMD results to Hologic Equivalent units

Table 1. Lunar DXA Systems

Measurement Site	Conversion Equation	Reference
Lumbar Spine	Hologic BMD= 0.918 x Lunar BMD – 0.038	1
Total Hip	Hologic BMD= 0.971 x Lunar BMD – 0.037	2
Femoral Neck	Hologic BMD= 0.8638 x Lunar BMD – 0.039	2
Trochanter	Hologic BMD= 0.8588 x Lunar BMD – 0.023	2

Table 2. Norland DXA Systems

Measurement Site	Conversion Equation	Reference
Lumbar Spine	Hologic BMD= 0.924 x Norland BMD + 0.077	1
Total Hip	Hologic BMD= 1.004 x Norland BMD + 0.020	2
Femoral Neck	Hologic BMD= 0.906 x Norland BMD – 0.012	2
Trochanter	Hologic BMD= 0.8697 x Lunar BMD + 0.067	2