There are many liver serum biochemical tests, mainly liver enzymes, bilirubin and serum proteins. Liver enzymes include transaminase, alkaline phosphatase and gamma transpeptidase. Serum liver enzymes (especially aminotransferases) and bilirubin reflect hepatocyte damage and have limited significance in expressing the functional status of the liver, so their inclusion in the “liver function test” is not accurate. True liver function includes the synthesis, catabolism and removal of toxins. The main clinical tests are serum albumin and prothrombin time, which reflect the ability of hepatocytes to synthesize albumin and prothrombin. A decrease in albumin or prothrombin time indicates a decrease in liver function, or a decrease in the number of functioning hepatocytes. Tests indicating liver injury can be clearly separated from tests expressing liver function, but in cases of liver injury (e.g. hepatitis), there are often varying degrees of abnormal liver function, and the more severe the liver injury, the more pronounced the decrease in liver function. What does an elevated glutaminase mean? Transaminases include glutaminase and glutathione. Glutaminase is found in hepatocyte plasma and elevated serum levels indicate that the enzyme is leaking from injured hepatocytes, and that there is a significant increase in minor damage to the cell membrane, which can be a sensitive indicator of inflammatory activity. The elevation can range from tens to thousands: those with strong inflammatory activity have a large elevation and an acute onset of disease; those with weak inflammatory activity have a small elevation and a slow onset of disease. Those with large elevations may develop more serious lesions, but if timely anti-inflammatory and enzyme-lowering treatment is given, the inflammation can subside and the lesions may not be serious. In acute hepatitis patients, the glutaminase is often in the thousands, but most of them get better in a few months; in many cirrhotic patients, the glutaminase is only 100 or less, can you say that the disease is less severe than acute hepatitis? Many patients with chronic hepatitis have only small fluctuations in glutaminase, but their disease continues to progress slowly, so a series of regular tests is more important than a momentary increase. Glutaminase is present in any tissue cell, and an elevated enzyme does not necessarily mean that there is liver damage; a soccer game can raise glutaminase when the legs are sore. However, glutaminase is most abundant in the liver and biliary system. If it exceeds 200, most of the diseases are hepatobiliary; if it exceeds 1000, it can only be hepatobiliary diseases. What does elevated glutaminase mean? Only 1/5 of glutaminase is present in the hepatocyte plasma, and about 4/5 is in the mitochondria (organelles that manage oxidation and energy within the cell). Glutaminase is significantly elevated when the mitochondria are damaged, reflecting the degree of hepatocellular disease. The magnitude of glutaminase elevation is generally less than that of glutaminase, but if it exceeds glutaminase and persists over time, it suggests chronicity and progression of the lesion. In alcoholic and drug-related liver disease, glutathione is mainly elevated, so the glutathione/glutathione ratio is >1.0; in viral hepatitis, the glutathione/glutathione ratio is <1.0, but when it progresses to cirrhosis, the ratio is >1.0, and even glutathione is normal while glutathione is elevated. Glutathione is found in many tissues, is more widely distributed, and is less specific. Glutathione is elevated in acute cardiac or skeletal muscle injury. What does an elevated alkaline phosphatase indicate? Alkaline phosphatase is found in many tissues including the liver, bile ducts, intestinal wall, bones, kidneys, placenta, and white blood cells. After 3 months of normal pregnancy, serum alkaline phosphatase levels can increase 2 to 4 times as the placenta grows, returning to normal only 3 weeks after delivery. In children and the elderly this enzyme is elevated, apparently in association with skeletal changes. If there is a simultaneous elevation of gamma transpeptidase, it means that alkaline phosphatase also comes from the hepatobiliary system and both are elevated due to hepatobiliary system disease; if bilirubin is also elevated, it is a bilious disease inside or outside the liver. What does elevated transpeptidase mean? Gamma transpeptidase is present in many tissues and is found in high concentrations in the liver, pancreas and kidneys. In liver disease, elevated gamma transpeptidase is an important indicator for the diagnosis of alcoholic liver disease in 30% of chronic viral hepatitis, 50% of active cirrhosis, and 70% of alcoholic liver disease. What does elevated bilirubin indicate? The sum of indirect bilirubin and direct bilirubin is total bilirubin. A mild increase in indirect bilirubin without an increase in transaminases is not uncommon in normal people; an increase in indirect bilirubin is also seen in jaundice when the red blood cells are lysed and the liver cells cannot metabolize it. Elevated direct bilirubin, along with elevated alkaline phosphatase and gamma transpeptidase, is seen in biliary diseases, including biliary obstruction and biliary hepatitis. Both direct and indirect serum bilirubin are elevated in hepatocellular lesions. Jaundiced viral hepatitis is typical of hepatocellular jaundice. What does a decrease in albumin mean? It is not only liver disease that affects albumin synthesis, but also nutritional status, thyroid and glucocorticoids; accelerated albumin degradation is seen in some diseases when it is lost from the kidneys, small intestine and ascites. Thus, serum albumin levels do not depend only on the functional state of the liver, and this test is non-specific for liver function. The normal adult liver synthesizes about 10 grams of albumin per day; degradation is slow and it takes 20 days for the serum level to decrease by half. Therefore, it does not decrease in acute liver disease; whereas in chronic liver disease it is an important indication of abnormal liver function. Patients with cirrhosis have only 3-4 grams of synthesis per day, and the degree of albumin reduction reflects the severity of liver disease and the length of the disease. What does a prolonged prothrombin time indicate? Prothrombin time is determined by the level of coagulation factors synthesized by the liver. With less synthesis of coagulation factors, prothrombin time will be prolonged, so it is an important indicator of the synthetic function of the liver, the severity of the lesion and the consequences of the disease. Serum prothrombin level decreases by half in as little as 12 hours, and assuming complete loss of hepatocyte synthesis, prothrombin decreases by 95% after 2 days, while albumin decreases by only 8%, so prolonged prothrombin time best reflects acute severe liver injury. However, there is no change in general liver damage, so it is not a sensitive liver function test. Serum liver biochemical tests are non-specific, and non-liver physiological and pathological factors may also show abnormal results of the test. Therefore, it is important to exclude causes other than the liver in the diagnosis of liver disease.