Category: Central DXA: (DXA, TBS)

3 - Enhanced precision of the new Hologic Horizon densitometer compard with the old Discovery model

Background: Previous publications suggested that the precision for the new Hologic Horizon densitometer might be better than for the previous Discovery model, but these observations were confounded by not using the same subjects and technologists on both densitometers. We sought to study this issue methodically by measuring in vivo precision in both densitometers using the same subjects and technologists.


Methods:
Precision study for the Horizon model (Hologic; Bedford, MA) was done by acquiring spine bone mineral density (BMD) twice on 30 patients, by the same technologist, using the same scanning mode. Precision study for the Discovery model was done the same way on the same day with the same patients and technologists. The pairs of data for each densitometer were used to calculate the LSC (least significant change) according to ISCD guidelines. The significance of the difference between LSC’s was assessed using a Wilcoxon Signed Rank test.


Results:
The precision was better for the Horizon than for the Discovery at the total spine, total hip, and 1/3 radius, although the difference did not reach statistical significance. As more vertebrae were excluded from analysis, the precision deteriorated on both densitometers. The precision between densitometers was almost identical when reporting only one vertebral body.
Site LSChorizon LSCDiscovery
Total hip 0.0211 0.0306
Femoral neck 0.0329 0.0335
1/3 radius 0.0284 0.0324
L1-4 0.0196 0.0232
L1-3 0.0220 0.0272
L1-2 0.0223 0.0345
L1 0.0446 0.0439


Conclusions:

1. The measurement of in vivo BMD on the new Hologic Horizon densitometer is more precise than on the older Discovery model, although this difference did not reach statistical significance.
2. The difference in precision of the spine BMD between the Horizon and Discovery models decreases as fewer vertebrae are included.
3. The measurement of spine BMD is less precise as more vertebrae are excluded, but still quite reasonable even when only one vertebral body is included.
4. These findings are substantially similar to previously published results which had used less rigorous methodology.

Alan O. Malabanan

Clinician
Beth Israel Deaconess Medical Center
Boston, Massachusetts

Elizabeth McNamara

Technologist
Beth Israel Deaconess Medical Center
Boston, Massachusetts

Emily Shaw

Technologist
Beth Israel Deaconess Medical Center
Boston, Massachusetts

Savoun Vath

Technologist
Beth Israel Deaconess Medical Center
Boston, Massachusetts

LaTarsha G. Whittaker

Technologist
Beth Israel Deaconess Medical Center
Boston, Massachusetts

Harold Rosen

Director - Osteoporosis Prevention and Treatment Center
Beth Israel Deaconess Medical Center
Boston, Massachusetts