Overview of Liver Function Tests

Liver function tests are a series of tests to evaluate liver health through blood tests. They are mainly divided into three categories:Liver enzyme indicators (such as ALT, AST)Reflects the degree of liver cell damage;Bilirubin and protein indicators (such as total bilirubin, albumin)Assess liver metabolic and synthetic functions;Other auxiliary indicators (such as GGT, ALP)Assists in the diagnosis of cholestasis or biliary tract disease. Test results need to be interpreted comprehensively in conjunction with clinical manifestations. Abnormal values may indicate diseases such as hepatitis, cirrhosis, or fatty liver.

Liver enzyme indicators: "alarm" of liver cell damage

Liver enzymes are the core item of liver function tests.Alanine aminotransferase (ALT)andAspartate aminotransferase (AST)It is a sensitive indicator. ALT mainly exists in liver cells, and its elevation is common in viral hepatitis or drug-induced liver injury; AST exists in both heart and muscle, and needs to be analyzed in conjunction with the ALT ratio. A mild increase may be related to staying up late or drinking alcohol, while a significant increase (such as more than 10 times) requires vigilance for acute hepatitis. In addition,Alkaline phosphatase (ALP)andγ-glutamyl transpeptidase (GGT)Elevated levels may indicate bile duct obstruction or alcoholic liver disease.

Bilirubin and protein: the liver’s “metabolic report card”

Bilirubin is divided intoTotal bilirubin, direct bilirubin and indirect bilirubin, jaundice may occur when it is elevated. High direct bilirubin is more common in biliary obstruction, and elevated indirect bilirubin may be related to hemolysis.AlbuminandprealbuminReflects the liver's synthetic ability, long-term low levels may indicate chronic liver disease;Prothrombin time (PT)Prolongation indicates a disorder in the synthesis of coagulation factors in the liver, which is common in late stages of liver cirrhosis. These indicators are important basis for evaluating liver function reserve.

Auxiliary indicators and comprehensive interpretation

Liver function tests need to be combined withCholinesterase (CHE)(Reduced in liver disease),Total bile acids (TBA)(sensitively reflects liver damage) and other auxiliary indicators. In addition,Alpha-fetoprotein (AFP)Although it is a tumor marker, it can also assist in liver cancer screening. You need to fast for 8-12 hours before the examination and avoid strenuous exercise or alcohol. When the results are abnormal, the cause needs to be further clarified through ultrasound, FibroScan, etc. The diagnosis cannot be made based on a single indicator.

Summary and Notes

Liver function tests are a barometer of liver health, but please note:Single minor abnormalityMay have no clinical significance;People who drink alcohol or are obese for a long timeIt should be monitored regularly;Hepatitis patientsIt is necessary to dynamically observe changes in indicators. Daily liver protection requires a balanced diet, limiting alcohol, and avoiding drug abuse. If the indicators continue to be abnormal, you should promptly go to the gastroenterology or hepatology department for treatment.

Quote sources:
1. "China Guidelines for the Prevention and Treatment of Chronic Hepatitis B (2022 Edition)" - Liver Disease Branch of the Chinese Medical Association
2. Mayo Clinic Liver Function Test Guidelines
3. Roche Diagnostics liver function test kit (product name: Cobas® ALT/AST)