(1) Indicators reflecting liver parenchymal damage Mainly include alanine aminotransferase (ALT), aspartate aminotransferase (AST), etc., of which ALT is the most commonly used and sensitive indicator, 1% of the hepatocytes undergo necrosis, the level of serum ALT can be elevated by a factor of 1. Continuous elevation of AST, with the value exceeding that of ALT is often indicative of severe parenchymal damage, which is a sign of aggravation of the degree of chronicity. (2) Reflects the severity of the damage to the liver parenchyma. (2) Reflect the bilirubin metabolism and cholestasis indicators, including total bilirubin (TBil), direct and indirect bilirubin, urobilirubin, urobilinogen, blood bile acids (TBA), γ-glutamyl transpeptidase (γ-GT) and alkaline phosphatase (ALP). When hepatocyte degeneration and necrosis, bilirubin metabolism disorder or intrahepatic cholestasis, the above indexes can be elevated. Indirect bilirubin can be elevated in hemolytic jaundice. (3) Indicators reflecting the synthetic function of the liver mainly include albumin, prealbumin, cholinesterase and prothrombin time and activity, etc. When long-term albumin and cholinesterase decrease, and prothrombin activity decreases, which cannot be corrected by supplementation of vitamin K, it means that the normal hepatocytes are gradually decreasing, and the function of hepatocytes synthesizing protein and coagulation factors is poor, and the reserve function of liver decreases, so the prognosis is not good. (4) Indicators reflecting liver fibrosis Mainly include type III pre-collagen (PIIIP), type IV collagen hyaluronic acid (HA), laminin (LN), etc. These indicators can assist in the diagnosis of liver fibrosis and early cirrhosis. (5) Indicators of liver coagulation function The liver can synthesize all the coagulation factors other than Ⅲ and factor a chain, which plays an important role in maintaining normal coagulation function. The synthesis of coagulation factors is reduced in patients with liver disease, and clinical bleeding of gums and nasal mucosa, skin bruises, and gastrointestinal bleeding may occur in serious cases. Generally speaking, the earliest and most reduced factor VII, followed by factor II and X. The last and least reduced factor is factor V. A. Prothrombin time (PT) The normal value is 11-15 seconds, and it is meaningful to prolong more than 3 seconds compared with normal control. Acute hepatitis and light chronic hepatitis PT is normal, severe hepatocellular necrosis and cirrhosis patients PT significantly prolonged.PT is a more sensitive indicator to reflect the degree of hepatocellular damage and determine the prognosis. B. Plasminogen activity (PTA) Normal value is 80%~100%. Its clinical significance is the same as PT C. Hepatic procoagulant activity test (HPT) is one of the methods to determine the reserve function of the liver, which can sensitively and reliably reflect the impaired synthesis of coagulation factors Ⅱ, Ⅶ and Ⅹ caused by liver damage. Clinical tests show that HPT decreases in patients with acute hepatitis, chronic active hepatitis, cirrhosis and subacute severe hepatitis at all stages of the disease. The more severe the disease, the lower the HPT. When liver disease develops to hepatocellular failure, its HPT are significantly reduced, generally more than less than 0.5. If the HPT gradually recovered sequentially, the prognosis is good. New items Recently, the relevant departments have added five new items of liver function tests, as follows: 1, glycocholic acid (CG): when the liver cells are damaged or cholestasis, the content of CG in the blood increases significantly, reflecting the damage to the liver cells is more sensitive than the ALT, which is commonly used in the clinic at present, and it can be used to find out the mild liver damage at an early stage, which is helpful in distinguishing the severity of the condition of chronic hepatitis. 2.Ferritin(SF)：Synthesized and stored in liver, SF synthesis can be increased by inflammatory reaction of hepatocyte, and SF can be released into blood by degeneration and necrosis of hepatocyte, the degree of increase of SF is in parallel with the degree of damage to hepatocyte, but it can be significantly reduced in severe hypoproteinemia and iron deficiency anemia. 3.Pre-albumin(PA)：It has certain significance for early detection of severe hepatitis and chronic liver damage. The more serious the disease, the lower the value. 4.Transferrin(TF)：It is a kind of glycoprotein synthesized by liver, and its main function is to run iron. TF is elevated in acute hepatitis and can be low in chronic hepatitis and cirrhosis. TF decreases in many other infections, while TF increases in iron deficiency anemia and the end of pregnancy. 5, bile acid (TBA): is the main organic anion excreted by the liver, its metabolism is mainly controlled by the liver, when liver function is impaired, its elevation is often earlier than bilirubin and obvious. Therefore, it can reflect liver damage more sensitively. Normal value ALT 0~40 AST 0~37 AST/ALT 0.80~1.5 GGT 7~32 Alkaline phosphatase (ALP) 53~128 TBILI 5.1~19.0 DBILI 0.0~5.1 IBILI 5.0~19.0 Indirect bilirubin (IBILI) 0.0~5.1 Indirect bilirubin (IBILI) 0.0~5.1 Indirect bilirubin (IBILI) 0.0~5.1 Indirect bilirubin (IBILI) 0.0~5.1 Indirect bilirubin (IBILI) 0.0~5.1 Indirect bilirubin (IBILI) 5.0~5.1 Indirect bilirubin (IBILI) 5.0~12.0 Total protein (TP) 60~80 Albumin (ALB) 35~55 Globulin (GLB) 15.0~35.0 Albumin to Globulin ratio (ALB/GLB) 1.20~2.00 Glucose (GLU) 3.89~6.11 Urea Nitrogen (BUN) 1.7~8.3 Creatinine (CRE) 53~108 Lactate dehydrogenase (LDH-L) 109~24.0 LDH-L (LDH-L) 109~24.1 LDH-L (LDH-L) 109~24.1 LDH-L) 109~24.1 LDH-L (LDH-L) 109~24.1 LDH-L) 109~24.2 LDH-L 109~245 Creatine kinase (CK) 24.0~195.0 Total cholesterol (CHOL) 3.35~6.45 Triglyceride (TRIG) 0.48~1.17 Uric acid (UA) 202~416 Reaction problems The physiological functions of the liver are extremely complex, so there are many different types of liver function tests, and doctors often choose a few representative liver function tests to understand Liver function, such as protein metabolism function test (serum protein electrophoresis, albumin/globulin ratio), bilirubin metabolism function test (including blood total bilirubin and direct bilirubin, urobilinogen and urobilirubin), liver dye excretion test as well as a variety of serum enzyme tests. However, liver function tests are not foolproof and have certain limitations. First of all, the sensitivity of liver function tests has a certain limit, and the liver has a strong compensatory reserve capacity, so a normal liver function test does not necessarily mean that there is no liver disease, in addition, some indicators in the liver function test lack specificity, so an abnormal liver function does not necessarily mean that there is liver disease. In addition, serum enzyme activity is a very important criterion, but it does not reflect liver function, and the enzyme index is only an estimation of hepatocyte integrity. In conclusion, liver function tests can only be used as an auxiliary means to diagnose diseases of the hepatobiliary system; in order to make a correct diagnosis of the disease, it must be combined with the medical history, physical examination and imaging tests, etc., to make a comprehensive and integrated analysis. Evaluation Criteria There are many methods of liver function tests, which illustrate the lack of specificity of certain test methods. When analyzing the results of liver function tests clinically, the following issues need to be considered in order to evaluate whether liver function is normal or not: (1) The liver has a large reserve capacity and a strong regenerative and compensatory ability. Therefore, a normal liver function test does not mean that the liver cells are not damaged. On the contrary, when liver function tests are abnormal, it inevitably reflects extensive liver lesions. (2) At present, there is no test that can reflect the whole picture of liver function, therefore, when certain liver functions are impaired, a certain appealing function test that is sensitive to it will show abnormality first, while other liver function tests may be normal. Therefore, several liver function tests are often done at the same time. (3) Some liver function tests are not unique to the liver. For example, aminotransferase and lactate dehydrogenase can also change when heart and bone exclusion muscle lesions occur, so when determining the results of liver function tests, attention should be paid to the exclusion of extra-hepatic diseases or factors. Precautions 1, before the liver function test can not eat, can not drink water, must keep fasting, fasting time is generally 8 to 12 hours. 2, the night before the liver function test can not drink alcohol, can not eat spicy food, can not eat greasy food, must be light. 3, the night before the liver function test can not stay up late, can not take medication, otherwise it may lead to elevated transaminases and abnormal liver function test. Significance of the examination Regular liver function examination is very necessary. Because the liver is the largest organ in the human body, it is responsible for a variety of physiological functions. When liver cells are damaged for various reasons, the metabolism of various substances in the liver cells can be abnormal, leading to changes in the levels of liver-related metabolites and acids in the blood. Clinical examination of liver function is aimed at detecting the presence or absence of liver diseases, the degree of liver damage, as well as identifying the causes of liver diseases, judging the prognosis and identifying the causes of jaundice. Liver function tests include alanine aminotransferase, glutamic aminotransferase, total protein, albumin, globulin, albumin/globulin, and total bilirubin. Liver function tests can help patients to detect and diagnose certain diseases at an early stage, whether they suffer from acute or chronic hepatitis, alcoholic liver, drug-induced hepatitis, fatty liver, cirrhosis, and diseases of the hepatobiliary system, etc. Citizens who want to have a liver function test should pay attention to the fact that blood must be drawn on an empty stomach for the test. Fasting time is generally 8-12 hours, especially for the first time to check liver function. It is better to abstain from alcohol the day before the blood test. Liver function tests have a certain relationship with diet, for example, drinking alcohol tends to increase the value of certain serum enzymes, and eating greasy food can increase blood lipids and so on. The cost of liver function test is related to the consumption level of each place, the number of test items, the test method, and the level of the hospital. The reference cost of liver function test is about tens of dollars to hundreds of dollars, different hospitals charge different costs, you can consult the local regular hospitals for specific costs. Liver function is to reflect the physiological function of the liver, liver function test is to detect whether there is any disease of the liver, the degree of liver damage, as well as to identify the causes of liver disease, to determine the prognosis and identify the causes of jaundice, etc. Several representative indicators are often selected. Several representative indicators are often chosen to understand liver function, such as protein metabolism function test, bilirubin metabolism function test, liver dye excretion test and various serum enzyme tests. These include bilirubin, albumin, globulin, transaminase, biliary enzymes, serum ammonia, and clotting time. Liver function tests are especially sensitive and important in determining liver diseases such as hepatitis and cirrhosis. When these lesions first affect the metabolic function, immune function, synthetic function of the liver, etc., which makes these and their sensitive indexes reflected in the liver function test. At the same time, liver function test also has certain limitations, liver function test can only be used as an auxiliary means to diagnose diseases of the hepatobiliary system. When evaluating the results of liver function tests, liver function must be considered comprehensively with clinical symptoms to avoid one-sidedness and subjectivity. Analysis of liver function test results 1. Causes of ALT elevation: (1) Acute and chronic viral hepatitis (2) Cholecystitis or biliary tract diseases (such as inflammation, stones, polyps, cancer, etc.) (3) Liver injury caused by alcohol consumption (4) Liver injury caused by drugs (5) Other factors causing ALT abnormality (fatty liver, liver cancer, etc.) (6) Viral hepatitis (Hepatitis B, Hepatitis C, Hepatitis A, etc.) 2. Analysis of ALT results: Increase of ALT>60u/L; acute stage of myocardial infarction, acute hepatitis, drug toxic hepatocellular necrosis, active stage of chronic hepatitis, active stage of cirrhosis, hepatocellular carcinoma, myocarditis, nephritis, myositis. 3.Analysis of ALT/AST ratio results: AST is mainly distributed in myocardium, followed by liver, skeletal muscle and kidney and other tissues. Since about 80% of AST exists in mitochondria, it is not as sensitive to hepatocellular injury as ALT, and the magnitude of elevation is not as large as ALT, but if AST is substantially elevated it means that hepatocellular injury is more serious. Therefore, the ratio of ALT/AST is often regarded as a diagnostic indicator and condition monitoring indicator in clinical practice. 4, γ glutamyl transpeptidase (GGT) results analysis: GGT is mainly from the hepatobiliary system, therefore, it is mainly a monitoring program for hepatobiliary diseases. (1) Liver inflammation: mild and moderate increase in GGT. (2) Other diseases of the liver and gallbladder: hepatocellular carcinoma, hepatic obstructive yellow bile, biliary cirrhosis, cholangitis, gallbladder polyps, gallstones, pancreatitis, pancreatic head carcinoma, biliary tract carcinoma, etc., GGT is significantly elevated. (3) Prolonged or heavy alcohol consumption can also lead to elevation of this enzyme. (4) Long-term acceptance of certain drugs such as phenobarbital, phenytoinna, antipyrine, oral contraceptives, etc. will also increase GGT. 5.Bilirubin result analysis: Bilirubin is the product of decomposition and destruction of senescent red blood cells in blood. It is divided into three types: total bilirubin, direct bilirubin, and indirect bilirubin. Therefore, the results of bilirubin measurement have 3 roles. (1) Direct and indirect bilirubin are markedly elevated when liver cells are damaged as in hepatitis. (2) In biliary tract diseases, especially gallbladder stones, biliary polyps, cholecystitis, etc., direct bilirubin is significantly elevated in the blood. (3) Hemolytic diseases increase the source of bilirubin in the blood, which is not processed by the liver, resulting in a significant increase in indirect bilirubin. 6. Analysis of the results of total protein, albumin and globulin: The amount of protein in the blood can reflect the function of the liver, if the protein decreases, it means that the synthesis function of the liver is impaired, which is a manifestation of a more serious condition, such as chronic active hepatitis, cirrhosis, liver failure and so on. Some non-liver diseases can also cause changes in blood proteins, so some physiological influences should be noted when analyzing the results. How to choose Physical examination knowledge: to go to the physical examination, when to check the liver function, you understand how to choose? Below, for you to introduce the choice of liver function tests: 1, when clinical suspicion of hepatitis or has been diagnosed as acute hepatitis need to further understand the extent of the lesion, you can test GPT (glutamic-propanic aminotransferase) or complex iodine test. Urine triple bile test, serum van den Berg test and bilirubin quantification. In the case of chronic hepatitis, in addition to the above tests, A/G (albumin-to-globulin ratio) and, if necessary, serum protein electrophoresis may be performed. Alkaline phosphatase can be tested if the patient is not jaundiced and other liver functions are normal and mild liver damage cannot be excluded. For primary hepatocellular carcinoma, in addition to general liver function tests, AFP (alpha-fetoprotein), γ-GT (γ-glutamate transpeptidase), AKP and other measurements can be performed to help clinical diagnosis. Before each larger surgery, generally check the serum GPT, A/G, if necessary, plasma prothrombinogen time to understand the condition of the liver, and make good preoperative preparation. 2.According to the condition, selecting certain liver function tests and reviewing them regularly for dynamic observation can reflect whether the treatment is effective or not to a certain extent. For example, when the condition of acute hepatitis improves, the GPT returns to normal; if the GPT fluctuates for a long time or continues to rise, it suggests that hepatitis has a tendency to slow down. Certain liver function tests have extrahepatic diseases, the results can also be seen abnormal, such as nephrotic syndrome, malignant tumors, etc., resulting in a decrease in total plasma protein and albumin; hyperthyroidism, etc., can be reduced serum cholesterol. And certain drugs, trauma, etc., can lead to serum transaminase elevation. Therefore, when selecting liver function tests and analyzing the results, they should be analyzed in conjunction with clinical specifics. When hepatitis is suspected clinically or acute hepatitis has been diagnosed and the extent of the lesion needs to be further understood, GPT (glutamic transaminase) or compound iodine test can be detected. Urine triple bile test, serum van den Berg test and bilirubin quantification. In the case of chronic hepatitis, in addition to the above tests, A/G (albumin-to-globulin ratio) and, if necessary, serum protein electrophoresis may be performed. Alkaline phosphatase can be tested if the patient is not jaundiced and other liver functions are normal and mild liver damage cannot be excluded. For primary hepatocellular carcinoma, in addition to general liver function tests, AFP (alpha-fetoprotein), γ-GT (γ-glutamate transpeptidase), AKP and other measurements can be performed to help clinical diagnosis. Before each larger surgery, generally check the serum GPT, A/G, if necessary, plasma prothrombinogen time to understand the liver, good preoperative preparation. 3.According to the condition, selecting certain liver function tests and reviewing them regularly for dynamic observation can reflect whether the treatment is effective or not to a certain extent. For example, when the condition of acute hepatitis improves, the GPT returns to normal; if the GPT fluctuates for a long time or continues to rise, it suggests that hepatitis has a tendency to slow down. Certain liver function tests have extrahepatic diseases, the results can also be seen abnormal, such as nephrotic syndrome, malignant tumors, etc., resulting in a decrease in total plasma protein and albumin; hyperthyroidism, etc., can be reduced serum cholesterol. And certain drugs, trauma, etc., can lead to serum transaminase elevation. Therefore, when choosing liver function tests and analyzing the results, they should be analyzed in conjunction with clinical specifics. Liver function test should be taken on an empty stomach Liver function is a routine test, all liver function tests are required to take on an empty stomach, this is because normal human blood contains a certain amount of large molecules of β and γ globulin, which can be combined with certain chemical reagents and precipitate, and small molecules of albumin and α1- globulin, which can prevent the precipitation of the production. When the prescribed chemicals are added to the serum of a normal person, because of the inhibitory effect of albumin, no precipitation or slight precipitation occurs, but patients with hepatitis B, because of the decrease of albumin and the increase of β1- and γ-globulin in the serum, the serum of patients with hepatitis B, the addition of chemicals, obvious precipitation occurs. That is to say, after eating before the liver function test, the composition of the serum will be changed, and after adding chemical reagents to the blood taken during the laboratory test, even the serum of normal people will be precipitated to varying degrees, especially after eating high-protein or high-fat food, it is more likely to be precipitated, and the results of the test will easily make the doctor misdiagnose the normal person as a hepatitis patient.