C telopeptides of type I collagen inpostmenopausal women: an experience in a Tunisian clinical laboratory

The purpose of study was to evaluate the interest of C-telopeptides of type I collagen [CTX] in the diagnosis of osteoporosis in postmenopausal women and to define its cut-off value. A transverse descriptive study enrolled postmenopausal women: 139 osteoporotic [G1] and 39 non osteoporotic [G2]. The 2 groups were defined by bone density measurement. The followmg markers were measured: serum alkaline phosphatase [ALP] bone alkaline phosphatase [bone ALP], serum C-terminal telopeptide of type I collagen [CTX]. Statistical analyses were performed using SPSS 10, 5. The corresponding estimation of sensitivity and specificity of CTX have been presented as receiver Operating Curve [ROC]. There was no difference in the measurement of ALP and bone ALP in the 2 groups but CTX was statistically higher in G1 compared to G2 [p<0.001]. The percentage of osteoporotic women [G1] with CTX values>0.500 ng/ml was higher than that of non osteoporotic women [G2]. We have established a ROC curve to find the cut-off value of CTX that enables the distinction between osteoporotic women with high level of bone remodelling, and non osteoporotic women. The cut-off value of CTX 0.55 pg/mi was the best; it associated best sensitivity and specificity. The total increase and significance for CTX was greater in the group of osteoporotic women and appeared therefore to be a good bone turnover marker in the diagnosis of osteoporosis in comparison with ALP and bone ALP. The cut-off value of CTX 0.55 pg/mi may improve the sensitivity and specificity of prediction of future fractures

[ interest of biochemical markers of bone turnover for monitoring treatment of postmenopausal osteoporosis]

Postmenopausal osteoporosis is especially female pathology, whose incidence increases with age. The purposes of this study are to evaluate the level of bone turnover by the determination of markers of bone formation [PAL, BAP] and marker of bone resorption [CTX] in the osteoporotic women, to study the correlations between bone biochemical markers, clinical parameters and radiological measurements and to assess the interest of biochemical markers in therapeutic monitoring after 6 months of antiresorptive treatment. The authors report a prospective study of 134 osteoporotic women classified in two groups according to the presence of osteoporotic fracture. Patients of the first group G[1] [n=102] with fractures, were treated by the bisphosphonates [risedronate], whereas the ones of the second group G[2] [n=32] without fractures, were submited to calcic supplementation and vitamin D. The analyses showed that the femoral and lumbar BMD were statistically lower in the presence of osteoporotic fractures. However, the values of CTX were statistically higher in the patients of G[1] group compared to those of the G[2] group [0,708 +/- 0,332 mg/ml versus 0,514 +/- 0,225 mg/ml]. The CTX were statistically correlated with the femoral and lumbar BMD [r = -0,21, p<0,05 and r = -0,348, p<0,001]. The hypovitminosis were observed in 50,98% [52/102] of women with osteoporotic fractures, whereas it was only 25% [8/32] in women without fractures. After 6 months of treatment by the bisphosphonates, the PAL, the BAP and the CTX have decreased with an average of, respectively, 19%, 46,5% and 62,9%. These variations were significantly more important in G[1] group. The biochemical markers of bone turnover, in particular those of the resorption [CTX], can predict the post-menopausal woman's bone loss evaluated by BMD, the risk of fractures and the efficiency of the bone treatments