Urine Test Predicts Risk of Bone Fracture

The urine test focuses on a molecule called urinary cross-linked N-telopeptide of type I collagen (NTX), which is formed when bone is broken down and is expelled from the body in a person's urine.

Scientists at University of Pittsburgh Graduate School of Public Health (PA, USA) analyzed information on more than 2,300 women, aged 42 to 52 years, who were either premenopausal or were going through the menopause at the start of the 7.6-year period of data collection. NTX was measured using the Vitros ECi; automated immunoassay (Ortho Clinical Diagnostics; Rochester, NY, USA and expressed as nanomoles of bone collagen equivalents per liter per nanomole of creatinine per liter (nM BCE/nM Cr). The lower limit of detection was 10 nM BCE/nM Cr.

Serum osteocalcin was measured in duplicate using the ELSA-OSTEO immunoradiometric assay (CisBio International; Codolet, France) that measures both the intact human osteocalcin molecule of 49 amino acids and the fragment corresponding to amino acids 25 to 37 of the native molecule. The lower limit of detection of the assay is 0.4 ng/mL. Women who experienced fractures had about a 10% higher baseline median NTX of 34.4 versus 31.5 nM BCE/nM Cr, but there was no difference in osteocalcin. Women with a baseline NTX greater than the median had a 45% higher risk of fracture.

The authors concluded that a higher urinary NTX excretion measured before menopause and across menopause is associated with a higher risk of fracture. The results are consistent with the pathophysiology of transmenopausal changes in bone strength. Jane A. Cauley, DrPH, a professor of epidemiology and lead author said, "Bone fractures, particularly in the hip, wrist and back have serious consequences, including disability and death. Knowing a woman's risk of fracture can help doctors determine the best course of action to protect her bones as she enters menopause, a time when estrogen deficiency negatively affects skeletal health." The study was published on August 13, 2012, in the journal Menopause.

Related Links:
University of Pittsburgh Graduate School of Public Health
Ortho Clinical Diagnostics
CisBio International