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Articles |
ciun1
1
Department of Biochemistry and Cardiovascular Research Institute, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands.
2
Hoffmann-La Roche Diagnostics, Basel 4070,
Switzerland.
a Address corresponding to this author at: Department of Biochemistry, University of Maastricht, P.O. Box 616, 6200 MD Maastricht, The Netherlands. Fax 31-43-367-0992; e-mail m.knapen{at}bioch.unimaas.nl
Background: Circulating osteocalcin is a well-known marker for bone formation, but none of the commercial kits currently available can be used in automated systems. Here we present the first semiautomated assay for human serum osteocalcin.
Methods: Polystyrene beads were coated with antibodies against the COOH terminus of osteocalcin and used in the COBAS® EIA System. Osteocalcin was detected with peroxidase-conjugated antibodies against the osteocalcin NH2 terminus.
Results: The time required to analyze an unknown sample was 60 min, with a lower detection limit of 4.5 µg/L and a linear doseresponse curve between 4.5 and 100 µg/L. The intraassay imprecision (CV) was 58% (n = 21); the interassay variation was 69% (n = 14). In samples from human volunteers and patients, data generated with the newly developed assay were comparable to those obtained with standard microtiter plate-based assays.
Conclusions: The coated beads assay may be implemented on fully automated analyzers, which not only may further reduce imprecision but may also substantially increase the applicability of osteocalcin as a marker for bone metabolism in the routine clinical setting.
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