This test card is used for quantitative determination of N-MID osteocalcin in human serum, plasma or whole blood in vitro. Human N-MID osteocalcin is the most important non collagen in bone matrix. Its molecular weight is about 5800 daltons and contains 49 amino acids. It contains at most three γ - carboxyglutamic acid residues (BGP), which are bone specific calcium binding proteins dependent on vitamin K. Osteocalcin is produced by osteoblasts in the process of bone formation, which depends on vitamin K (γ - carboxyglutamic acid residue), and vitamin D3 can promote osteocalcin production. Part of osteocalcin produced by osteoblasts is absorbed into bone matrix, and part of osteocalcin is released into peripheral blood circulation. Accordingly, the content of osteocalcin in serum or plasma is related to the rate of bone turnover, so osteocalcin is called the index of bone formation. Therefore, the determination of the content of N-MID osteocalcin in human serum, plasma or whole blood is of great significance for the detection of osteoporosis, hypercalcemia and other bone metabolic diseases.