Assessment and Recommendations on Factors Contributing to Preanalytical Variability of Urinary Pyridinoline and Deoxypyridinoline‪.‬

Biochemical bone markers can provide a valuable tool in the management of metabolic bone diseases. Their most recognized application in clinical practice is for monitoring treatment for osteoporosis as an adjunct to bone mineral density measurements. Other applications that have been investigated include their use as a diagnostic tool for bone diseases other than osteoporosis and as predictive markers for bone loss and the risk of bone fracture (1-3). Biochemical markers are available to assess both bone formation and bone loss (resorption). Because most metabolic bone diseases are characterized by an increase in bone resorption, these particular biochemical markers are of special interest. Our focus in this review will be exclusively on the pyridinium cross-links pyridinoline (PYD;10 hydroxylysylpyridinoline) and deoxypyridinoline (DPD; lysylpyridinoline) because they are part of an extensive laboratory standardization program at the CDC designed to improve the measurement of biochemical markers and risk factors associated with selected chronic diseases. A description of other bone markers, including other resorption markers, such as type I collagen telopeptide breakdown products, is provided in several reviews (4-7). One of the main issues hampering the interpretation of PYD and DPD results for clinical use is preanalytical and analytical variation (8). The effects of analytical variability can be minimized through standardization of results of laboratory measurements by controlling imprecision through the use of good laboratory practices and by validating proper method calibration through appropriate traceability to reference methods, using suitable reference materials. These strategies have already demonstrated their benefit for other analytes, such as cholesterol, and are currently being implemented for PYD and DPD, as stated above, as well as for other bone markers (9).