Clinical reproducibility of dual energy x-ray absorptiometry.
Dual energy x-ray absorptiometry is a technique advocated for the measurement of bone mass throughout the skeleton, and recently it has been used to measure changes in periprosthetic bone mass after joint replacement. The accuracy and precision of the method in clinical patient populations have not been firmly established. This study sought to establish the short-term reproducibility of measurements made with dual energy x-ray absorptiometry of multiple sites in a large sample of elderly patients with rheumatic disease. Reproducibility was assessed in the lumbar spine and in three femoral sites in 69 patients participating in a longitudinal clinical trial. In each patient, absorptiometry was performed twice in the same day at as many as five time points over a 2-year period. The mean (+/- SD) baseline bone density was 0.783 +/- 0.128 g/cm2 for the femoral neck and 1.015 +/- 0.218 g/cm2 for the lumbar spine. The correlations between the duplicate baseline measurements of the spine were excellent (r = 0.9936, p < 0.001) and were stable over the 2-year period; the mean difference between the duplicate baseline measurements was 1.82 +/- 1.54% and the mean coefficient of variation was 1.29%. Measurements in the femur were much less precise; these values were 3.61 +/- 3.14% and 2.55% in the femoral neck, 3.66 +/- 4.35% and 2.59% in the greater trochanter, and 5.28 +/- 5.61% and 3.73% in Ward's triangle. This study evaluated the short-term reproducibility of dual energy x-ray absorptiometry in a clinical population.(ABSTRACT TRUNCATED AT 250 WORDS)