Markers of bone turnover for the prediction of fracture risk and monitoring of osteoporosis treatment: a need for international reference standards. od Vasikaran, S, Eastell, R, Bruyère, O, Foldes, A, Garnero, P, Griesmacher, A, McClung, M, Morris, H, Silverman, S, Trenti, T, Wahl, D, Cooper, C, Kanis, J, IOF-IFCC Bone Marker Standards Working Group