Objectives: C-telopeptide crosslaps (CTX) and bone-specific alkaline phosphatase (BAP) do not provide sufficient sensitivity and specificity for diagnosis of osteoporosis. Cathepsin K (CatK), osteoprotegerin (OPG), and receptor activator of nuclear factor κB ligand (total (t) and soluble (s) RANKL) play an important role in bone metabolism. Thus serum levels of biochemical markers, each or in combination, may be useful in diagnosis of osteoporosis.
Study design: In total, 121 healthy women, 27 premenopausal women aged between 20 and 45 years, and 94 postmenopausal women aged 59-81 years, all free of known skeletal disorders were included. They underwent bone density measurement and measurement of biochemical markers.
Main outcome measures: Based on WHO criteria, women were stratified in four groups (premenopausal: healthy; postmenopausal: healthy, osteopenia, osteoporosis), and their levels of CatK, OPG, RANKL, CTX and BAP were analyzed.
Results: Using WHO criteria 21 postmenopausal women had normal bone mineral density (BMD), 49 had osteopenia and 24 had osteoporosis. There were no significant correlations of CatK, OPG and RANKL with BMD (T-score) in age-adjusted analysis, but for BAP and CTX. ROC analyses resulted in poor diagnostic validity of all parameters. The best result - also confirmed by discriminant analysis - was yielded by BAP (AUC=0.646 [0.510; 0.781]). A combination of variables did not significantly improve the diagnostic power.
Conclusions: Baseline serum levels of BAP, CTX, CatK, OPG, sRANKL or tRANKL alone or in combination are not suitable to distinguish osteoporotic from non-osteoporotic postmenopausal women with sufficient accuracy.
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