A summary of common laboratory test indicators for liver disease

The liver is the largest substantial glandular organ in the human body.
It has important functions such as material metabolism, biotransformation, secretion and excretion, and synthesis of coagulation factors
.

The three major nutrients are metabolized in the liver.
The liver is also a place for the storage and metabolism of multiple vitamins.
It participates in hormone inactivation, bilirubin and bile acid metabolism
.

This article summarizes common laboratory test indicators such as liver metabolism, enzymology, coagulation function, etc.
, for your reference
.

Yimaitong compiles and organizes, please do not reprint without authorization
.

Protein metabolism Except for gamma globulin produced by B lymphocytes and plasma cells, most plasma proteins are synthesized in the liver
.

When the liver is extensively damaged, the synthesis of these plasma proteins is reduced
.

1.
STP, ALB, GLB: More than 90% of total serum protein (STP) and albumin (ALB) are synthesized by the liver.
Therefore, the two are important indicators that reflect the liver's synthetic function
.

Due to the strong compensatory ability of the liver and the long half-life of albumin (about 17-23 days), the liver damage needs to reach a certain degree.
After a period of time, the serum albumin level will change.
Therefore, serum albumin does not reflect acute liver disease.
Good indicator
of
Globulin (GLB) is a mixture of multiple proteins, partly synthesized by the liver.
In laboratory tests, GLB=STP-ALB, which is closely related to the body's immune function and plasma viscosity
.

The clinical significance of changes in serum protein levels are shown in Table 1
.

Table 1 Clinical significance of serum protein indicators 2.
PA: Serum prealbumin (PA) has a shorter half-life than other plasma proteins (about 2 days), so the reduction of PA reflects liver cell damage earlier than albumin, and prealbumin can be used as an early diagnosis , It is a sensitive laboratory indicator for prognosis and efficacy observation, but it is easily affected by nutritional status and liver function
.

3.
ChE: Cholinesterase (ChE) is produced by the liver and then secreted into the blood, reflecting the liver parenchyma's ability to synthesize protein
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In chronic hepatitis, if the indicator continues to decrease, it indicates that the prognosis of the disease is poor
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ChE is more sensitive than albumin to reflect changes in the condition, and the value of ChE rises rapidly as the condition improves
.

However, the ChE value will also decrease in malnutrition, infection, anemic disease, and organophosphate poisoning, which should be judged
.

4.
Blood ammonia: The liver tissue is severely damaged, and the increased blood ammonia enters the brain tissue to cause cell degeneration, swelling and degeneration; blood ammonia can also cause excitatory and inhibitory neurotransmitter disorders, leading to neurocognitive disorders and other obstacles
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Elevated blood ammonia is of high value in the diagnosis of hepatic encephalopathy, but patients with normal blood ammonia cannot rule out hepatic encephalopathy
.

Excessive compression of the tourniquet, long time after blood sampling, and transportation of blood samples at high temperatures may cause a false increase in blood ammonia
.

Therefore, the venous blood should be collected at room temperature and sent for testing at low temperature immediately, and the measurement should be completed within 30 minutes, or refrigerated at 4°C after centrifugation, and testing should be completed within 2 hours
.

Lipid Metabolism The liver is the center of lipid metabolism and the main place for the synthesis and decomposition of various lipids
.

Although abnormal blood lipid detection is not used as a diagnostic indicator of liver disease, liver disease is closely related to lipid metabolism, such as fatty liver
.

1.
CHOL: Almost all tissues of the human body can synthesize cholesterol, but the liver is the main place to synthesize cholesterol.
When the liver is severely damaged, the total cholesterol in the blood (CHOL) decreases; Increased phospholipid content
.

2.
TG: The liver synthesizes but does not store triglycerides (TG).
TG needs to be assembled with apolipoproteins, phospholipids, and cholesterol to form very low-density lipoproteins (VLDL), which are secreted into the blood and transported to extrahepatic tissues
.

Malnutrition, poisoning, lack of essential fatty acids, lack of protein, etc.
, the hepatocytes can not synthesize VLDL, which leads to the accumulation of triglycerides in the liver and fatty liver
.

3.
LP-X: Obstructive lipoprotein X (LP-X) is a lipoprotein that is abnormal in the blood during cholestasis, and the result of normal serum examination is negative
.

When biliary obstruction, blood LP-X increases, which is a sensitive and specific indicator of cholestasis.
In addition, its content is related to the degree of cholestasis
.

Bilirubin Metabolism 1.
TBIL, DBIL, IBIL: Most of the bilirubin in the serum is derived from the hemoglobin derivation after aging red blood cells are destroyed
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The liver has the functions of uptake, transformation and excretion in the metabolism of bilirubin
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Direct (bound) bilirubin (DBIL) is glucuronated in the liver, and indirect (unbound) bilirubin (IBIL) is not glucuronated in the liver.
The sum of the two is total bilirubin ( TBIL)
.

The process of bilirubin metabolism in the body is shown in Figure 1
.

In clinical practice, the level of bilirubin is commonly used to determine the type of jaundice, as shown in Table 2
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Figure 1 Bilirubin metabolism process Table 2 Judging the type of jaundice based on the level of bilirubin 2.
Urinary bilirubin: DBIL is water-soluble and appears in the urine through the glomerular basement membrane, while IBIL cannot appear in the urine.

.

Normal people have a negative urine bilirubin test.
If it is positive, it indicates an increase in blood bilirubin, which can help bilirubin to determine the type of jaundice
.

Pay attention to the impact of alkalosis on the positive test
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3.
Urobilinogen: only a small amount of urobilinogen enters the blood and is excreted through the kidneys during the enterohepatic circulation of bilirubin
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The increase of urobilinogen requires consideration of increased red blood cell destruction and intestinal obstruction
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Pay attention to the influence of eating and urine acidity on the test results
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Bile acid metabolism TBA: When the liver's function of uptake, secretion, and transport of bile acid is impaired and other diseases that can cause changes in bile acid metabolism occur, the concentration of bile acid in the blood will increase significantly, and its sensitivity and specificity are high
.

For example, when acute hepatitis occurs, the serum total bile acid (TBA) concentration rises sharply, and compared with other clinical test indicators, the bile acid level returns to the normal process more slowly; during the recovery period of acute viral hepatitis, the serum TBA level after meals It is one of the most sensitive detection indicators.
If the serum TBA concentration continues to increase after a meal, it indicates that viral hepatitis is transforming into chronic hepatitis; in addition, serum TBA detection is also the detection of chronic hepatitis liver damage and cholestasis, and early diagnosis of liver cirrhosis and toxicity A sensitive indicator of liver disease
.

 Serum enzymes and isoenzyme examination 1.
ALT, AST: Alanine aminotransferase (ALT), mainly in the liver, followed by skeletal muscle, kidney, myocardium and other tissues, mainly in non-mitochondria
.

Aspartate aminotransferase (AST) is mainly found in the heart muscle, followed by liver, skeletal muscle and kidney tissues, mainly in mitochondria
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The half-life of ALT is 47h, and the half-life of AST is 17h.
The sensitivity of ALT is higher than that of AST
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Serum ALT and AST are elevated, which is seen in the damage of the above tissues
.

However, the degree of elevated transaminase has nothing to do with the severity of liver damage
.

Clinically, the AST/ALT ratio is used to determine the course and severity of the disease, and to evaluate the prognosis.
If the ratio increases (normal value 1.
15), the more severe the liver cell damage
.

In most patients with chronic liver injury (>6 months), AST/ALT≤1.
15, the ratio of liver cirrhosis and liver cancer increases, and it is related to the degree of fibrosis
.

However, with the exception of chronic alcoholic hepatitis, if there is a history of drinking and serum AST/ALT>2, the diagnosis of alcoholic hepatitis is considered
.

2.
ALP: Most of the alkaline phosphatase (ALP) in serum comes from the liver and bones
.

The physiological conditions of increased ALP are seen in bone growth, pregnancy, growth, maturation, and postprandial secretion of fat
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Pathology seen in extrahepatic biliary obstruction, bone diseases such as bone tumor, fracture healing, dystrophy, gastroduodenal damage
.

The detection of total ALP level has poor specificity for the diagnosis of liver disease, and ALP needs to be determined by enzyme typing or combined with other liver function markers for analysis
.

3.
GGT: Most of the γ-glutamyltransferase (GGT) in serum mainly comes from the hepatobiliary system, which is distributed on the side of the capillary duct of hepatocytes and the entire bile duct system.
When the intrahepatic synthesis is hyperactive or the bile excretion is blocked, the serum GGT Increase
.

In patients with chronic hepatitis and liver cirrhosis, if the GGT continues to increase, it may indicate disease activity or deterioration
.

4.
LDH: The clinical detection significance of lactate dehydrogenase (LDH) lies in isoenzymes.
Lung contains more LDH3, and myocardial injury LDH1 and LDH2 increase; liver substantial damage LDH5 increases, LDH5>LDH4, bile duct obstruction is not involved LDH5<LDH4 for hepatocytes
.

And the tumor growth rate has a certain relationship with the degree of LDH increase
.

Coagulation function test 1.
Coagulation factor: Except for the coagulation factor IV which is Ca+, the other coagulation factors are all proteins
.

Most coagulation factors and coagulation inhibitors are synthesized in the liver
.

Vitamin K dependent factors (II, VII, IX, X) have a short half-life (such as VII half-life of 1.
5-6h).
In the early stage of liver damage, vitamin K-dependent coagulation factors are significantly reduced, so coagulation factors reflect liver cells earlier than albumin Damage
.

However, note that coagulation factor VII and fibrinogen are acute-phase reactive proteins, and their increase is related to factors such as tissue necrosis and inflammation
.

2.
PT: Prothrombin time (PT) reflects the content of coagulation factors II, V, VII, and X, with poor sensitivity, but it can judge the prognosis of liver disease
.

PT is the most important predictor of the prognosis of acute liver injury.
For example, if the serum total bilirubin in patients with acute viral hepatitis is greater than 257umol/L, the PT is prolonged by more than 4s, indicating the occurrence of severe liver injury, and we should be alert to the occurrence of liver failure
.

If the PT is prolonged for more than 20s, it indicates that the patient has a high risk of death
.

The PT of patients with chronic hepatitis is generally normal, and a prolonged PT indicates the possibility of decompensation of liver cirrhosis
.

3.
APTT: In severe liver disease, the synthesis of coagulation factors IX, X, XI, XII is reduced, resulting in prolonged activated partial thromboplastin time (APTT)
.

It is also the first choice for monitoring heparin therapy
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In addition, patients with liver disease may show a decrease in the number of platelets or abnormal function
.

For example, alcohol and hepatitis virus can inhibit the production of bone marrow megakaryocytes; platelet consumption increases during DIC
.

In patients with cholestasis, the absorption of fat-soluble vitamin K is impaired, and the relevant coagulation factors cannot be activated, which can cause coagulation disorders
.

Intake and excretion test 1.
Indigo Green Retention Rate Test (ICGR): decreased hepatic blood flow, decreased hepatocyte number, biliary obstruction, and decreased ICG clearance K value
.

The retention rate of ICG in the blood R increases
.

Reflects liver reserve function, and has guiding significance for liver surgical resection
.

2.
Lidocaine metabolism test: Lidocaine is metabolized by the liver to monoethylglycyldiphenyl MEGX.
The measurement of MEGX concentration reflects the liver reserve function and can predict the survival of the transplanted liver after liver transplantation
.

Liver fibrosis index examination MAO, PH, PⅢP, CⅣ: Monoamine oxidase MAO can accelerate the cross-linking of collagen fibers, prolyl hydroxylase PH is a collagen fiber synthetase, and type III procollagen amino terminal peptide (PⅢP) is a procollagen receptor peptide Enzyme fragmentation products, MAO, PH, PⅢP activities are commonly used to assess the degree of liver fibrosis
.

In addition, type IV collagen (CIV) is formed by the degradation of basement membrane, which can be used as an indicator to reflect collagen degradation.
It can be used for early diagnosis of liver cirrhosis, and it can also predict the efficacy of interferon and anti-hepatitis virus antibodies.
If serum CIV>250ug/ml is considered, interference Vegetarian treatment is ineffective
.

Liver tumor index examination 1.
AFP: Alpha-fetoprotein (AFP) is currently the most commonly used biochemical test index for the diagnosis of primary liver cancer.
Normal human serum AFP is less than 25ng/ml, and the diagnostic threshold for primary liver cancer is generally set as 300ng/ ml
.

After liver cancer is completely removed by surgery or effective chemotherapy, serum AFP can quickly fall to normal within 1-2 months
.

If AFP rises, it usually indicates recurrence of liver cancer
.

2.
AFU: The positive rate of α-L-fucosidase (AFU) in the diagnosis of liver cancer is 80%, and the specificity is 70%.
Some scholars believe that AFU can be used as a prognostic indicator before HCC resection, and in early liver cancer cases The serum concentration of AFU is related to tumor size
.

3.
GT: Studies have confirmed that γ-glutamyltransferase (GT) has high sensitivity and specificity in the diagnosis of HCC, especially for small liver cancer or patients with negative AFP expression
.

In addition, carcinoembryonic antigen and carbohydrate antigen, Golgi glycoprotein 73 (GP73), glypican 3 (3GPC3), and serum protein prothrombin (DCP) are all commonly used clinical tumor markers.
Combined detection of tumor markers has important clinical value in the diagnosis of primary liver cancer
.

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