Serum alkaline phosphatase (ALP) is an enzyme widely distributed in human tissues such as liver, bone, intestine, kidney and placenta. It is more abundant in liver and bone, produced by osteoblasts, and excreted from the biliary system via the blood to the liver. Therefore, ALP determination is mainly used to diagnose diseases of the hepatobiliary and skeletal systems, and is an important indicator of extrahepatic biliary obstruction, intrahepatic occupying lesions and rickets. The clinical significance of increased ALP mainly lies in: 1. Hepatobiliary diseases: obstructive jaundice caused by pancreatic head cancer or bile duct stones, hepatocellular carcinoma, primary biliary cirrhosis, jaundiced hepatitis, etc. In general, chronic hepatitis has varying degrees of fibrosis, and ALP can be mildly to moderately increased. ALP is a commonly used indicator in the diagnosis of biliary system diseases, and this enzyme is significantly elevated in cholestatic hepatitis and extrahepatic obstruction, but ALP can only indicate obstructive biliary lesions, and cannot identify whether the obstruction is benign or malignant. In the case of biliary tract diseases, the increase in ALP production and decrease in excretion may cause an increase in serum ALP. 2, bone disease: due to bone damage or disease, high concentrations of alkaline phosphatase contained in osteoblasts are released into the blood, causing an increase in ALP, such as osteochondrosis, rickets, osteoclastic carcinoma, osteoporosis, etc.. Because this enzyme is active in bone tissue, some physiological conditions such as pregnant women, fracture healing period, serum alkaline phosphatase will also increase. 3, other conditions such as leukemia, hyperthyroidism, serum alkaline phosphatase can also be elevated.