Standardization of marker assays--pyridinoline/deoxypyridinoline

The hydroxypyridinium collagen crosslinks pyridinoline and deoxypyridinoline (Dpd) are released during the degradation of some mature collagens. Assays for the peptide forms of these crosslinks in blood and urine and for the free and total crosslinks in urine have been developed. Currently there is no internationally accepted reference standard for use in any of these assays. Recently the criteria and strategy for the preparation of a Dpd standard have been described. Using the UV molar absorptivity of 5160 L/mol/cm at 294 nm in 0.1 mol/L HCl and purity checked by NMR spectroscopy, mass spectrometry and elemental analysis sufficient quantities of this reference standard will have to be prepared. Protection from photolysis is essential to ensure stability of the reference preparation. This reference preparation will be suitable for calibration of immunoassays for free Dpd and for HPLC assays of free and total Dpd. The assays for peptide forms of the crosslinks have used standards prepared either by enzymatically digesting collagen or synthesis of oligopeptides. The problem of standardization of some of these peptide assays may be resolved if a reference preparation of digested bone collagen can be produced and appropriately characterised.