Evaluation of peripheral dual energy X-ray absorptiometry: comparison with single photon absorptiometry of the forearm and dual energy X-ray absorptiometry of the spine or femur.

An evaluation of the Osteoscan peripheral dual energy X-ray absorptiometer (pDXA) was carried out to compare its performance with those of a single photon absorptiometer (SPA) (Molsgaard Medical ND1100A) and a dual energy X-ray absorptiometer (DXA) (Lunar DPX alpha) of the spine or femur. In 57 patients, correlation between bone mineral content (BMC) of the forearm at the ultradistal (UD) site by pDXA and by SPA was high (r = 0.94). Comparisons were also made with spine and femur bone mineral density (BMD) DXA measurements. The correlation of z-scores of UD BMD with z-scores for lumbar spine L2-L4 was r = 0.63 (n = 73 patients); and with z-scores for neck of femur was r = 0.72 (n = 33). With the Osteoscan the measurement error coefficient of variation in vivo was 2.6% for BMC, 1.8% for BMD at the ultradistal site; 2.1% for BMC and 1.9% for BMD at the mid-distal site. Repeat measurements were made of the European forearm phantom; precision for SPA was slightly better than either pDXA or Lunar DXA. The Osteoscan has the potential for a rapid throughput of patients and is not affected by calcification and degenerative changes that can corrupt DXA measurements on the anteroposterior spine in older women.