Abstract
Although bone mineral density (BMD) measurements at the lumbar spine and/or the proximal femur using dual energy X-ray absorptiometry (DXA) are recommended for the diagnosis of osteoporosis, DXA measurements at the distal radius are often performed instead for the medical checkup in Japan. Therefore, we evaluated the validity of distal radius DXA as an osteoporosis screening test.
Thirty women who were identified with a low BMD during their medical checkup underwent BMD measurements at the distal third radius (RADIUS), the lumbar spine (SPINE) and the proximal femur (HIP) within the duration of one year. The median age of the subjects was 64 years (49–87 years). The correlation and difference between the BMD values in the different regions were retrospectively assessed by comparing the percentage difference from the young adult mean (%YAM).
The %YAM of RADIUS was significantly correlated with those of SPINE and HIP (r=0.6055, p=0.0004 and r=0.5490, p=0.0017, respectively). The %YAM of RADIUS was, however, significantly lower than those of SPINE (p<0.0001, mean difference 10.13 points, 99% CI 5.22–15.05) and HIP (p<0.0001, 9.53, 4.44–14.62). By contrast, %YAMs of SPINE and HIP were statistically not different (p=0.7100, 0.60, −3.80 to 5.00). According to the significant low %YAM of RADIUS, the false-positive rate was 33.3% and 25.3% for osteopenia in SPINE and HIP, respectively. The %YAMs of RADIUS, SPINE and HIP were comparably correlated with the FRAX 10-year major osteoporotic fracture probability (r=−0.6292, −0.5498, −0.5864, respectively).
In conclusion, DXA at the distal radius may be an acceptable alternative for osteoporosis screening. However, it should be performed with caution, because this test has a relatively high false-positive rate. If the medical facilities allow for it, SPINE and/or HIP are recommended.
