N-TELOPEPTIDE IN URINE

CLINICAL UTILITY:

The discovery of urinary cross-linked N-telopepetides of type I collagen (NTx) has provided a specific biochemical marker of human bone resorption. The NTx molecule is specific to bone due to the unique amino acid sequences and orientation of the cross-linked alpha-2 N-telopeptide. Generation of the NTx molecule is mediated by osteoclasts on bone, and is found in the urine as a stable end product of degradation.

Elevated levels of urinary NTx indicate elevated bone resorption. Clinical research has demonstrated that elevated bone resorption is the primary cause of age-related bone loss and that low bone mass often results in osteopenia and is the major cause of osteoporosis. Loss of bone mass occurs when bone resorption levels are elevated above bone formation levels. Osteoporotic fractures are reported to be the major source of increased morbidity and mortality in older women.

Clinical studies have supported the use of urinary NTx levels to monitor the response to treatment of patients with diagnosed osteoporosis. A study was conducted to determine the ability of the assay to monitor the effect of antiresorptive therapy in patients with Paget's disease. Paget's patients treated with antiresorptive therapy should have a >30% reduction in urinary NTx levels from baseline after 3 months of treatment.

Paget’s disease of bone is a common skeletal disorder in which there is a focal proliferation of the normal cellular components of bone. Paget’s disease is more prevalent than once thought with the incidence rate in certain populations at 3%-4% in middle-aged patients and 10%-15% in the elderly. This disease does not affect young individuals. The majority of patients with Paget’s disease have no symptoms and often go undiagnosed unless an abnormal X-ray or serum alkaline phosphatase level is found in the course of a medical evaluation for unrelated reasons. The most common complaints in symptomatic patients are pain and deformity.

METHOD DESCRIPTION:

For the quantitative measurement of the cross-linked N-telopeptides of type I bone collagen (NTx) in human urine, we usea competitive-inhibition enzyme-linked immunosorbent assay (ELISA).

REFERENCE RANGE:

Children, years: 0 – 1: 102-4769 nM BCE/mM Creatinine; 2 - 5 years: 34-1752 nM BCE/mM Creatinine; 6 - 10 years: 90-1356 nM BCE/mM Creatinine; 11 - 15years: 34-2158 nM BCE/mM Creatinine; 16 - 20 years: 34-780 nM BCE/mM Creatinine. Adult Males: 14 - 87 nM BCE/mM Creatinine. Premenopausal females: 5-65 nM BCE/mM Creatinine.

SPECIMEN REQUIREMENTS:

Either a single urine collection other than a first morning void or a 24 hour urine collection may be used.