K-Postn Assay New Tool to Assess Fracture Risk in Postmenopausal Women

Cathepsin K digestion (K-Postn) may serve as a strong independent predictor of incident low-trauma fractures in postmenopausal women independent of bone mineral density (BMD) measurements and the Fracture Risk Assessment Tool (FRAX) algorithm, according to a recent study published in the Journal of Bone and Mineral Research.¹

Researchers identified and recruited 695 postmenopausal women in Geneva currently participating in an ongoing cohort study on the predictive factors of fracture risk. Dietary, FRAX, blood serum periostin, and BMD were assessed.

There were no significant differences in dietary intake, anthropometric assessments, physical activity, and vitamin D levels between women who had sustained a fracture and those with no history of fracture. The fracture group had a higher K-Postn level at baseline compared to the non-fracture group (P <.001).

During the study, 66 participants sustained at least 1 incident low-trauma fracture, with 9 classified as vertebral fractures and 57 as nonvertebral fractures.

Total periostin was not found to be associated with fractures (HR per SD increase: 1.19; 95% Cl, 0.89-1.59, P =.24).  However, K-Postn was statistically significantly higher in the fracture group compared with the nonfracture group (P <.001) and was also significantly associated with fracture risk (HR per SD increase: 2.14; 95% CI, 1.54-2.97, P <.001).  Further, the addition of K-Postn to areal BMD or FRAX increased the fracture prediction value of these tests (BMD + K-Postn compared to BMD alone: P =.001; FRAX + K-Postn compared to FRAX alone: P =.005).

Based upon this study, postmenopausal women with high circulating K-Postn blood levels are at higher risk for incident low-trauma fractures and can be identified independent of BMD and FRAX.  Therefore, K-Postn may be valuable in the identification of subjects at high risk for fractures.

Limitations

The study was conducted in 1 location (Geneva) and only included postmenopausal women.  Studies conducted in men and premenopausal are needed to validate the predictive accuracy of the test and generalize the results. In addition, the participants were relatively healthy, without serious chronic diseases or history of cancer within the last 5 years.

Reference

Bonnet N, Biver E, Chevalley T, Rizzoli R, Garnero P, Ferrari SL. Serum levels of a cathepsin-K generated periostin fragment predict incident low-trauma fractures in postmenopausal women independently of BMD and FRAX [published online August 2,2017]. J Bone Min Res. doi:10.1002/jbmr.3203