Introduction< /p>
Liver function test is one of the most common clinical test items, including a number of test indicators. The clinical significance of different test indicators is different, reflecting Hepatocyte injury, bilirubin metabolism and liver synthesis function. These indicators are mainly used to diagnose and evaluate diseases of the hepatobiliary system and to assess the severity of related diseases. This article summarizes the commonly used liver function test indexes and their clinical significance.
Indicators reflecting liver cell damage
1. Detection of serum aminotransferase levels
Alanine aminotransferase (< strong>ALT) and aspartate aminotransferase (AST) reflect liver cell damage Important indicators. Under physiological conditions, ALT and AST are usually lower than 40 U/L. When hepatocytes are damaged, the permeability of hepatocyte membrane increases, and ALT and AST in the cytoplasm are released into the plasma, resulting in an increase in serum ALT and AST.
Various liver diseases can cause mild to moderate elevations in transaminases , therefore, transaminase elevations below moderate (<300 U/L) are nonspecific.
Sharp elevation of ALT (>1000 U/L) is common in acute viral hepatitis, toxic or drug-induced liver injury, acute ischemic liver disease, etc.
Severe autoimmune hepatitis and hepatolenticular degeneration can also lead to a sharp increase in transaminases, but accompanied by an increase in autoimmune antibodies or abnormal copper metabolism.
The AST/ALT ratio decreased in mild hepatitis, and increased in severe hepatitis, cirrhosis and liver cancer. An AST/ALT ratio >1.2 indicates a poor prognosis.
2. Cholestasis Detection
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Alkaline phosphatase (ALP): ALP in serum mainly comes from liver, bone Therefore, ALP is often used as one of the inspection indicators for related liver diseases. Various intrahepatic and extrahepatic bile duct obstructive diseases, such as bile duct obstruction caused by gallstones, primary biliary cholangitis (PBC), intrahepatic cholestasis, etc., can cause a significant increase in serum ALP.
γ-glutamyl transpeptidase( GGT): GGT is mainly distributed in kidney, liver and pancreas, but serum GGT mainly comes from liver, so elevated GGT indicates liver disease, especially biliary tract disease. In patients with bile duct obstructive disease, GGT is significantly elevated; in acute and chronic hepatitis and liver cirrhosis, GGT is slightly to moderately elevated.
Indices reflecting bilirubin metabolism
< strong>Bilirubin: Bilirubin is a product of the decomposition and destruction of senescent red blood cells in the liver and spleen in the blood circulation. Total bilirubin (TB) includes two forms, indirect bilirubin (IB) and direct bilirubin (DB). Measurement of serum bilirubin can help detect jaundice that is not yet observable with the naked eye, often reflecting liver cell damage or cholestasis.
Indices reflecting liver synthesis function
Albumin: Albumin is synthesized in the liver. The level of albumin reflects the anabolic and reserve function of the liver, and is also an indicator for evaluating the severity of liver cirrhosis and judging the prognosis. When the synthesis function of the liver is reduced, the serum albumin is significantly reduced, which is common in the decompensated stage of liver cirrhosis and acute and chronic liver failure.
Prothrombin Time (PT): PT is another index to evaluate the synthesis function of the liver. This index detects the blood coagulation time. Blood coagulation requires the participation of coagulation factors. Most of the coagulation factors are synthesized by the liver. Therefore, PT can reflect the synthesis reserve function of the liver to a certain extent. The normal value of PT is 11-15 seconds, and it is clinically meaningful to prolong the PT value by more than 3 seconds. Patients with severe hepatocyte necrosis and cirrhosis have significantly prolonged PT. In addition, prolonged PT can also be seen in patients with oral anticoagulant therapy, disseminated intravascular coagulation (DIC), or vitamin K deficiency.
cholesterol: About 70% of endogenous cholesterol is synthesized in the liver, when When liver synthesis is impaired, blood cholesterol levels will decrease.
How to assess a patient’s liver function?
In addition to the above test indicators, the evaluation of liver function should also be combined with the patient’s symptoms, signs, imaging examinations and comprehensive judgments of pathology. The Child-Pugh score (Table 1) was used to grade and evaluate liver function, which is convenient for clinical diagnosis and treatment decisions.
Child-Pugh A (5-6 points)
Child-Pugh B (7-9)
Child-Pugh grade C (10-15 points)
Table 1 Child-Pugh score of liver function span>