Serum CrossLaps One Step ELISA. First application of monoclonal antibodies for measurement in serum of bone-related degradation products from C-terminal telopeptides of type I collagen.

We have developed a two-site ELISA for measurement in serum of bone-related degradation products derived from C-terminal telopeptides of type I collagen. The assay is based on the application of two highly specific monoclonal antibodies against the amino acid sequence of AHD-beta-GGR, where the aspartic acid residue (D) is beta-isomerized. In a one-step incubation procedure, the degradation products containing cross-linked diisomerized EKAHD-beta-GGR peptides are captured by a biotinylated antibody and a peroxidase-conjugated antibody. The generated complex is then bound to the streptavidin surface via the biotin conjugate. Desalted urinary antigens are used for standardization, and parallelism is observed with serum samples. Results are obtained in <2.5 h, and both inter- and intraassay imprecision are <8%. The serum CrossLaps concentration was 1748+/-740 pmol/L (mean +/- SD) in premenopausal women (n = 65) and 2952+/-1325 pmol/L in a group of healthy postmenopausal women (n = 169). The Serum CrossLaps One Step ELISA was capable of detecting a highly significant (P <0.001) effect of hormone replacement therapy in a retrospective study involving 22 postmenopausal women.