Comparing BMD results between two similar DXA systems using the generalized least significant change.

Area of Science:

• Medical Imaging
• Bone Densitometry
• Osteoporosis Research

Background:

• Clinical densitometry practice faces challenges comparing bone mineral density (BMD) measures across different densitometers.
• Accurate tracking of bone density changes is crucial for patient management and treatment efficacy.

Purpose of the Study:

• To evaluate the application of the generalized least significant change (GLSC) method for comparing BMD measures between different densitometry systems.
• To assess the impact of system differences on the sensitivity to detect changes in bone density.

Main Methods:

• Followed the GLSC procedure, quantifying system precision and in vivo cross-calibration.
• Scanned 30 participants twice on a Hologic QDR-4500A and a Hologic Discovery/W at the hip and spine.
• Analyzed precision, average BMD differences, correlation coefficients, and the magnitude of change required for significance.

Main Results:

• System precisions were similar, with average BMD differences less than 1% for key regions.
• Correlation coefficients between systems ranged from 0.96 to 0.98.
• The magnitude of change needed for significance was twice as large for intersystem (6-10%) compared to intrasystem (3-6%) comparisons.

Conclusions:

• The GLSC method provides a framework for comparing BMD measures across different densitometry systems.
• A substantial loss in sensitivity to change is observed when comparing scans from different systems, even those with similar technology.
• Current policies for comparing scans from systems of the same technology may require revision to account for intersystem variability.