Comparison of BMD Measurements by Dual Energy X-Ray Absorptiometry and Multiple Sites to BeamMed Speed-of-Sound Measurements at the Forearm in Patients With Gaucher Disease

Dual-energy X-ray absorptiometry (DXA) is the current gold standard for the clinical diagnosis of osteoporosis based on measurement of bone mineral density (BMD) [Baim et al, 2006]. As DXA technology continues to evolve, new instruments and technologies are introduced [Shepherd et al, 2005], making it necessary to document how these advances compare to prior densitometers.

The purpose of this study is to assess bone mineral density (BMD) comparability and precision using a standard Hologic DXA unit and the quantitative ultrasound-driven speed-of-sound (SOS) BeamMed technology. The physical and mechanical properties of bone that are measured by SOS are different than bone density measured by DXA and reflect bone strength and elasticity [Goossens et al, 2008]. The cohorts will be patients with Gaucher disease [Zimran & Elstein, 2010] who currently are requested to undergo BMD evaluation only bi-annually [Mistry et al, 2011], partly because of the radiation of DXA scans (admittedly low relative to standard X-rays and CT). Patients with Gaucher disease are at added risk for osteonecrosis and pathological fractures but to date no biomarker or technology has been able to predict which patients are imminently at risk. Because the option of disease-specific but very costly enzyme replacement therapy (ERT) [Barton et al, 1991] is predicating on the estimated risk of severe disease, predicting skeletal damage (especially osteonecrosis at the femoral neck, FN) because of osteopenia or osteoporosis has clinically relevant ramifications [Mistry et al, 2011]. Additionally, it has been shown that there is a correlation between low BMD at the lumbar spine (LS) and anemia in patients with Gaucher disease [Khan et al, 2012], so that with correction of anemia with ERT it is hoped that there will be amelioration of BMD values, and this too would be worth performing at closer intervals.

The least inconvenient and shortest evaluation for BMD is at the forearm. For approximately a year, all patients at the Gaucher disease have had DXA forearm evaluations when undergoing routine testing. It is the intention of this study to prospectively compare forearm SOS results [Olszynski et al, 2013] with those from the standard DXA equipment with the possibility of using SOS as a quantitative measure of bone integrity on a more regular basis.

The strategy will be to measure forearm BMD by DXA and SOS by BeamMed for comparison of accuracy and comparability and secondarily to assess the values achieved at the forearm relative to standard DXA evaluations at the FN and LS.

Patients who arrive at the Gaucher Clinic for routine monitoring that includes DXA evaluation of BMD at FN, LS, and forearm will be requested to consent to undergo SunBeam evaluation at the forearm as well. The same DXA hardware and software (Hologic, Bedford, MA) will be used for all examinations as have been employed by the Gaucher Clinic since August 2011.