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Oregon Osteoporosis Center
All rights reserved

The FRAX® Patch

Update 2/4/2009:The FRAX® has been updated to incorporate the calculations performed by the "FRAX® Patch." You may now enter brand of DXA machine and BMD in g/cm² directly into the FRAX® website. Separate use of the "FRAX® Patch" is no longer required.

For more information on the FRAX® tool, click here.

FRAX® (www.shef.ac.uk/FRAX/) is a tool developed by the World Health Organization to make estimates of fracture probability in postmenopausal women and older men using a combination of clinical risk factors with or without bone mineral density (BMD) measurements.

The BMD values used in the development of the FRAX® algorithm were femoral neck measurements from the NHANES III Caucasian female normative database, updated in 1998 (Kanis 2008, Looker 1998). This database is composed of scans made with Hologic brand densitometers, but the NHANES reference database included on Hologic DXA scanners uses data from the original 1995 NHANES III dataset (Looker 1995) which has slightly different mean and SD values for calculating T-scores and Z-scores.

Additionally, many densitometers use a male normative database to calculate T-scores for men, and some centers use ethnic-specific databases for T-score calculations. However, adjustments for gender and ethnic differences in the relationships between BMD values and fracture risk are built into the FRAX® model, so these T-scores are inappropriate to use with FRAX®.

Because of this history of the development of the FRAX® model, none of the current DXA machines provided the correct T-score or Z-score values to use with earlier versions of FRAX®.

The FRAX® Patch was a downloadable program devised to address these problems. Developed by the Oregon Osteoporosis Center with the support of the National Osteoporosis Foundation and WHO Fracture Risk Task Force and input from the American DXA manufacturers, the FRAX® Patch solved the discrepancies described above by first transforming non-Hologic DXA femoral neck BMD values (in g/cm²) to Hologic-equivalent BMD values using the Lu equations and then calculating the T-score with the 1998 NHANES III data used by FRAX®. The resultant T-score was appropriate for use in earlier versions of the FRAX® tool.

As of February 2009, the FRAX® website began incorporating the calculations performed by the FRAX® Patch described above. Users are now asked to provide the brand of DXA instrument and BMD in g/cm² rather than T- or Z-scores. These changes eliminate the need to use the FRAX® Patch.

Although it is no longer needed in order to use the FRAX® tool, you can click here if you would still like to download the FRAX® Patch.

Michael McClung, MD
Director
Oregon Osteoporosis Center
Ned Mossman, MPH
Associate Director, DXA Laboratories
Oregon Osteoporosis Center

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Copyright ©2013 Oregon Osteoporosis Center. All rights reserved.