This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. To determine the best method for obtaining blood for the measurement of matrix Gla protein and for the assessment of vitamin K deficiency status by the hydroxyapatite binding assay. To determine the stability of the MGP antigen in blood through repetitive freeze/thaw cycles and during storage at room temperature and in the cold room.