Does osteoporosis classification using heel BMD agree across manufacturers?
The lack of standardization in bone mineral density (BMD) measurements is known. Several studies have been carried out to cross-calibrate the axial dual X-ray absorptiometry (DXA) devices. Recently, a number of peripheral DXA (pDXA) densitometers have been introduced. In this study we evaluated the agreement between two heel DXA devices on BMD and T-scores. A total of 99 females aged 21-78 years (ca. 16 per decade) had their non-dominant heel BMD measured using the PIXI (Lunar Inc.) and the Apollo (Norland Medical) pDXA scanners. The mean BMD values were 0.492 and 0.607 g/cm(2) and the mean T-scores using manufacturers' specified reference data were -0.07 and -0.25 for the PIXI and Apollo, respectively. Both the BMD and T-score intermachine relationships were highly correlated but showed significant nonidentity slopes and non-zero offsets. The diagnostic comparison on T-scores resulted in 86% agreement between the instruments (weighted kappa score of 0.550). Normalizing the reference peaks and SDs using this study's young adult population BMD results removed the systematic T-score disagreement. We found that PIXI and Apollo are highly correlated. Differences in BMD values are mainly due to different region of interest (ROI) definitions and additional T-score disagreement reflects the difference in normative databases.
Osteoporosis and Arthritis Research Group, Department of Radiology, University of California at San Francisco, San Francisco, CA, USA. Mikayel.Grigorian@oarg.ucsf.edu
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Grigorian
J A
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Shepherd
X G
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Cheng
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Njeh
J O
JO
Toschke
H K
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Genant
D015502:Absorptiometry, Photon / Q000295:instrumentation / Q000379:methods / Q000592:standards*; D000328:Adult; D000368:Aged; D015519:Bone Density / Q000502:physiology; D002111:Calcaneus; D005260:Female; D006801:Humans; D016014:Linear Models; D008875:Middle Aged; D010024:Osteoporosis / Q000145:classification / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging / Q000706:statistics & numerical data; D012015:Reference Standards