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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)

Using rheumatoid arthritis patients who were receiving gold as models, we evaluated the renal effects of the chronic administration of very low doses of a nephrotoxic drug. The heavy metal gold has been shown to increase urinary enzyme excretion when it is given in usual doses for the treatment of rheumatoid arthritis. It is not clear whether the increased urine enzyme excretion caused by long-term drug therapy represents injury to the kidney or whether it is merely an effect of the drug. Urinary N-acetyl-beta-glucosaminidase and renal tubular cell excretion rates were measured in 19 patients who were receiving chronic treatment with gold and with nonsteroidal anti-inflammatory drugs for rheumatoid arthritis, in 10 patients who were receiving nonsteroidal anti-inflammatory drugs, and in 8 healthy control subjects. No subjects showed evidence of kidney disease. Both renal tubular cell and enzyme excretion rates were elevated in the gold-treated group. This showed that there was increased renal tubular cell turnover in this group, which suggests low level renal tubular injury and not merely an effect of the usual dose of gold.