Clinical Use: Free PYR and DPD are normally excreted in the urine, and larger quantities are excreted when bone resorption is increased. In contrast, when bone resorption is inhibited by bisphosphonate, oestrogen, or calcitonin therapy, the excretion of fPYR and fDPD is decreased. All available data indicate that fPYR and fDPD derive only from bone matrix degradation and thus are markers of bone resorption, not bone formation. The assay for pyridinium collagen cross-links is useful as a sensitive and specific marker in the diagnosis and management of bone loss in osteoporosis. The cross-links assay is also useful in measuring bone resorption in other metabolic bone diseases such as primary hyperparathyroidism and Paget's disease.

Patient preparation: fPYD and fDPD have a marked circadian rhythmn, with highest values seen between 02:00 and 08:00 and reaching a nadir between 14:00 and 23:00. A fasting second void urine should be collected between 08:00 and 10:00 and the result reported corrected for urine creatinine. A baseline pre-treatment measurement is required if assessing response to antiresorption therapy.

Sample requirements: Collect urine in a sterile universal container with no preservative. Send by first class post avoiding weekends. Minimum sample requirement - 10 ml urine.

	free Pyridinoline\Creatinine Ratio		free Deoxypyridinoline\Creatinine Ratio
	Reference Range	Units	Reference Range	Units
Male	5.0 - 21.8	nmol/mmol	0.4 - 6.4	nmol/mmol
Pre-menopausal	7.8 - 21.2	nmol/mmol	1.8 - 6.7	nmol/mmol
Post-menopausal	7.1 - 31.8	nmol/mmol	1.5 - 8.6	nmol/mmol

Additional information on urine free Pyridinoline and its clinical use can be found here: urine free Pyridinoline .

Additional information on urine free Deoxypyridinoline and its clinical use can be found here: urine free Deoxypyridinoline .

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