on behalf of the European Federation of Clinical Chemistry and Laboratory Medicine Working Group on Biological Variation and IOF-IFCC Committee on Bone Metabolism 2020, ' European Biological Variation Study (EuBIVAS) : within-and between-subject biological variation estimates of β-isomerized C-terminal telopeptide of type I collagen (β-CTX), N-terminal propeptide of type I collagen (PINP), osteocalcin, intact fibroblast growth factor 23 and uncarboxylated-unphosphorylated matrix-Gla protein—a cooperation between the EFLM Working Group on Biological Variation and the International Osteoporosis Foundation-International Federation of Clinical Chemistry Committee on Bone Metabolism ', Osteoporosis International, vol. 31, no. 8, pp. 1461-1470 . https://doi.org/10.1007/s00198-020-05362-8 Osteoporosis International, 31(8), 1461-1470. Springer London Osteoporosis international, 31(8), 1461-1470. Springer London