The Osteomark NTx assay
is a competitive-inhibition enzyme linked immunosorbant assay
(ELISA) that uses microwells in strips as the solid phase onto
which NTx has been absorbed.
NTx in the patient sample competes with the NTx absorbed on the
solid phase for binding sites on a horseradish peroxide labelled
monoclonal antibody.
The amount of antibody bound is inversely proportional to the
amount of NTx in the sample.
The NTx concentration in the patient sample is determined
spectrophotometrically and calculated from a standard calibration
curve.
In urine, ELISA results are expressed in nM of bone collagen
equivalents (nM BCE) per mM of creatinine. In serum, ELISA results
are expressed in nM BCE, i.e. no correction for creatinine is
necessary.