CLINICAL USEFULNESS OF SERUM TARTRATE-RESISTANT ACID-PHOSPHATASE-ACTIVITY DETERMINATION TO EVALUATE BONE TURNOVER

The study was carried out to evaluate the clinical validity and usefulness of serum tartrate-resistant acid phosphatase (TRAP) activity determined using an improved spectrophotometric assay. Enzyme activity was measured in 84 normal subjects and in 109 patients with common metabolic bone diseases. Mean values of serum TRAP activity in male subjects (n = 19; 10.4 +/- 2.15 U l-1) were not significantly different from those found in female subjects (n = 65; 10.8 +/- 1.8 U l-1). In the latter group mean values were significantly raised in post-menopausal subjects (10.5 +/- 2.0 U l-1; p < 0.01) compared with mean values in pre-menopausal women (8.45 +/- 1.8 U l-1). We found a significant inverse correlation between serum TRAP activity values and bone mineral density (BMD) measured both at an ultradistal radial point (n = 33, r = -0.506; p < 0.01), and at the lumbar spine (n = 57, r = -0.261; p < 0.05). Mean serum TRAP activity values in patients with metabolic bone diseases were: primary hyperparathyroidism, n = 30: 14.2 +/- 4.89 U l-1, p < 0.001 vs normal subjects; chronic maintenance haemodialysis, n = 19: 17.4 +/- 6.7, p < 0.001; metastatic cancer, n = 13: 21.2 +/- 6.3, p < 0.001; post-surgical hypoparathyroidism, n = 10: 9.9 +/- 1.8, NS; involutional osteoporosis, n = 20: 12.5 +/- 2.3 p < 0.001; Paget's disease, n = 10: 16.8 +/- 3.5, p < 0.001; osteomalacia, n = 7: 19.5 +/- 3.31, p < 0.001. The results of the study suggest that the measurement of serum TRAP activity may be clinically useful to assess bone turnover.