Evaluation of a fully automated serum assay for total N-terminal propeptide of type I collagen in postmenopausal osteoporosis.

BACKGROUND: Biochemical markers of bone turnover can provide prognostic information about the risk of fracture and may be useful for monitoring efficacy of antiresorptive and anabolic therapy in osteoporosis. We evaluated the performance of a fully automated assay for serum total N-terminal propeptide of type I collagen (P1NP), a marker of bone formation.
METHODS: Serum P1NP was measured on the Elecsys 2010 automated analyzer (Roche) in 230 healthy premenopausal women, age 30-49 years, 179 postmenopausal women with osteoporosis participating in the previously published 1 year randomized Parathyroid Hormone and Alendronate for Osteoporosis study of full-length parathyroid hormone (PTH 1-84, >100 microg/day subcutaneously; n = 119) or oral alendronate 10 mg/day (n = 60), and 64 healthy men, age 40 to 65 years.
RESULTS: The within-run and between-run (total) imprecision (CVs) were < or =1.7% (n = 20) and 4.4% (n = 15), respectively. The median within-person variability of results (3 measurements over 3 months in 15 postmenopausal women) was 7.2%, resulting in a least significant change (LSC) value of 20%. Serum P1NP concentrations were 74% (P <0.0001) higher in postmenopausal women than in premenopausal controls. After 3 months of treatment, 83% and 88% of patients treated with PTH 1-84 and alendronate, respectively, demonstrated changes of serum P1NP that exceeded the LSC.
CONCLUSION: The automated assay for serum total P1NP is precise and sensitive enough to detect changes that exceed the LSC in a majority of postmenopausal women after 3 months of treatment with PTH 1-84 or alendronate. Because of its convenience and high throughput, this bone formation marker may be useful for the monitoring of patients with osteoporosis.