Can't understand the physical examination report? These indicators can help you understand liver function

Author: Qiu Zewu, Chief Physician of the Fifth Medical Center of PLA General Hospital

Reviewer: Guo Shubin, Chief Physician, Beijing Chaoyang Hospital, Capital Medical University

Liver function tests are routine items in health checkups, but many people do not understand the meaning of the various indicators on the test report after receiving it. In fact, the height of the arrow on the test report is a signal from the liver, and liver function needs to be evaluated from four aspects, namely damage indicators, synthesis function, detoxification function and transport function.

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1. Damage indicators

Various pathogenic factors may cause liver cell damage. After the damaged liver cells dissolve, the enzymes inside will be released into the blood, causing the corresponding indicators to increase abnormally. Common enzymes are as follows.

The first is alanine aminotransferase and aspartate aminotransferase, which are ALT and AST in the physical examination report. Early liver damage is often manifested as elevated ALT, but if AST is higher than ALT, it indicates that the body may have chronic diseases, such as chronic hepatitis, cirrhosis and liver cancer.

At the same time, the AST/ALT ratio is also meaningful. It is particularly valuable for differential diagnosis and prognosis judgment of acute and chronic hepatitis. It can not only distinguish whether a person has chronic hepatitis, but also judge the metastasis and development of the disease, whether it is worsening or improving, spreading or alleviating. If it is acute hepatitis, the AST/ALT ratio is less than 1; if it is chronic hepatitis, the AST/ALT ratio is greater than 1. However, alcoholic liver disease is mainly characterized by elevated AST.

The second is alkaline phosphatase, which is ALP in the physical examination report. Clinical studies have shown that there is a certain relationship between the liver and osteoporosis. In addition, the liver and gallbladder are closely connected, so the ALP index is mainly used in the diagnosis and differentiation of bone and hepatobiliary system diseases, especially in the differential diagnosis of jaundice.

Other studies have shown that 75% of patients with long-term cholestasis have significantly elevated ALP, which is 4 times higher than the upper limit of normal. If the value continues to rise, it may be due to obstructive jaundice or biliary stones, or it may be due to a tumor that causes partial bile duct obstruction.

Next is γ-glutamyl transferase, or GGT in the physical examination report. The GGT in normal human serum mainly comes from the liver, generally 3 to 50 U/L. If the physical examination report shows that the serum GGT is elevated, it means that the synthesis of GGT in the liver may exceed the normal range, or bile excretion is blocked.

For example, obstructive jaundice can cause GGT to be unable to be excreted normally, thus flowing back into the blood and causing an increase in GGT. When a patient suffers from primary liver cancer, it can also cause GGT to be synthesized in the liver beyond the normal range, causing a significant increase in GGT.

Therefore, GGT is often used to identify hepatobiliary diseases and drug-induced liver injury.

Finally, there is lactate dehydrogenase, or LDH in the physical examination report. LDH is non-specific and exists in the liver, brain tissue, and myocardial cells. However, when liver function is impaired, LDH will increase along with ALT and AST, so it can be used as auxiliary evidence of liver damage.

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2. Synthesis function

The liver is the "chemical factory" of the human body, with extremely vigorous metabolism. A large amount of nutrients will enter the liver for "deep processing" after being absorbed by the intestines. Therefore, serum protein (ALB) and prealbumin (PALB) on the physical examination report are often used as indicators to evaluate the synthetic function of the liver.

ALB is the main indicator of liver protein synthesis function. When the liver is severely damaged or even liver failure occurs, ALB will drop significantly. In addition, long-term difficulty in eating or insufficient nutrient supply can also cause ALB to slowly drop.

PALB is different. It has a small molecular weight and a short half-life. In the early stages of liver damage, the increase and decrease of PALB are more obvious, making it a sensitive indicator for identifying early liver damage.

3. Detoxification function

The liver is the main detoxification organ in the human body. It can catalyze reactions through corresponding enzymes, turning poisons into non-toxic or low-toxic substances with high solubility, which are finally excreted from the body with bile or urine, thereby protecting the body from damage to a certain extent.

The degree of damage to the liver's detoxification function can be comprehensively judged by indicators such as coagulation function, albumin and bilirubin. For example, some patients have other diseases and their GGT levels increase significantly during medication, but other indicators do not increase significantly, indicating that the liver damage caused by the medication is relatively large.

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4.Transfer Function

Indirect bilirubin (IBIL) and glucuronic acid combine in the liver to form direct bilirubin (DBIL), which is responsible for the transport of cholesterol between peripheral tissues and the liver.

If DBIL in the blood increases, it means that the liver's transport function is abnormal, indicating that the liver may be damaged or blocked. For example, obstructive jaundice is mainly caused by elevated DBIL. At this time, the bile duct is blocked and bile excretion is not smooth, resulting in intrahepatic bile stasis.

Another example is hepatocellular jaundice, when liver cells are damaged and bile ducts are destroyed, both are released into the blood at the damaged site, causing IBIL and DBIL to increase at the same time. However, if IBIL alone increases, it indicates a blood problem.

In short, the various liver function indicators on the physical examination report can help you judge your own liver health. Only by properly understanding liver-related knowledge can you love and protect your liver in life.