[Biochemical markers of bone remodeling in assessment of osteoporosis]

The diagnostic significance of biochemical markers of bone remodelling is limited and it should always be evaluated together with results of other methods. Unlike bone densitometry, biochemical markers do not reflect bone mass and cannot be therefore used in diagnosis of osteoporosis. Markers enable for differential diagnostics of metabolic and neoplastic bone diseases and can be used for assessment of activity of bone disease and its monitoring. Different markers reflect aspects of bone remodelling. The sensitivity and specificity of the markers differ according to the type of bone disease and its treatment. The application of markers in monitoring treatment in individual patients requires an acceptable long-term biological variability of the marker (C.V. < 12%). In postmenopausal osteoporosis, osteocalcin measurements suffice in assessment of activity of the disease and for monitoring treatment. Lack of improvement in the marker can indicate poor compliance of the patient, a diagnostic error or an and-organ resistance to treatment. The biochemical measurement predicts changes in bone mass about one year prior to bone densitometry, thus enabling for decision concerning urgency of therapeutic intervention. In individual patients, however, a single measurement of a biochemical marker cannot be used to predict long-term changes in bone mass. Osteokalcin is cleared from the circulation by kidney and cannot be used to assess bone remodelling in chronic renal failure patients. This is not true with bone-specific alkaline or acid phosphatase isoenzymes. Low serum osteocalcin concentrations have special significance in hypercortisolism. Considering their high cost, the markers should be clinically applied under specified indications and only when standardised.