Blood tests for liver tests: what is included?

A screening study aimed at assessing the functional state of the biliary system and liver is an analysis of liver function tests. Diagnostics are performed by taking blood. It includes a number of mandatory indicators: AST, ALT, GGT, ALP, protein, bilirubin. In addition to the listed indicators, it is possible to check the lipid spectrum, which shows the state of fat metabolism in the body.

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Indications for the procedure

Liver function tests are performed when clear criteria are met:

• Disruptions in the functioning of the gastrointestinal tract.
• Dyspeptic syndrome.
• Metabolic disorders.
• Hepatitis.
• Endocrine pathologies.
• Chronic diseases of the liver and biliary tract.
• Increased serum iron levels.
• Excess body weight.
• Changes in the hepatobiliary system on ultrasound.
• Intoxication.
• Recent transfusion of blood or blood components.
• Evaluation of the treatment being carried out.

Preparation

To obtain reliable test results, it is necessary to prepare for blood donation. 48 hours before the test, you should avoid fatty foods, stop drinking alcohol, and stop smoking. The last meal should be no earlier than 8-10 hours before blood donation.

What tests are included in liver function tests?

Biochemical tests check blood for various liver pathologies, allow to determine the causes of the disease, make the correct diagnosis and select treatment. At the same time, there are diseases in which liver tests are carried out in combination with other studies: cancerous liver lesions, acute hemolysis, acute drug-induced hepatitis A-E.

ALT

Alanine aminotransferase is an enzyme found in liver parenchyma cells – hepatocytes. ALT is found in the kidneys, skeletal muscles and heart muscle. It is involved in protein metabolism. Its increased value is a specific sign of hepatocyte breakdown. The enzyme acts as a catalyst for the reversible transfer of alanine from amino acid to alpha-ketoglutarate.

Alanine is an amino acid that quickly transforms into glucose. Thanks to it, the energy potential of the brain and central nervous system increases. The substance strengthens the immune system, promotes the production of lymphocytes, regulates the metabolism of sugars and acids. The highest concentration of ALT is observed in the liver and kidneys, then in skeletal muscles, spleen, pancreas and heart.

The level of alanine aminotransferase is determined by a biochemical blood test. ALT indicators allow you to identify liver problems before their pronounced symptoms appear. As a rule, diagnostics are carried out when hepatitis is suspected, to check the condition of the organ after long-term use of medications and other toxic substances. There are mandatory indications for this study:

• Increased fatigue and weakness.
• Yellowness of the skin.
• Pain and discomfort in the abdomen.
• Flatulence over a long period of time.
• Nausea and vomiting.

Liver tests for ALT are used to monitor the dynamics of treatment in order to promptly identify improvements or deterioration in the patient's condition. The analysis is also necessary in the presence of risk factors for liver damage, for example: diabetes, excess weight, abuse of alcoholic beverages or drugs that destroy hepatocytes.

For analysis, venous or capillary blood is collected. The study is carried out on an empty stomach, the last meal should be 12 hours before its delivery. Failure to comply with this rule leads to false results.

The norm for marker enzymes for the liver depends on the patient’s age:

• Newborns up to 5 years old – no more than 49 U/L.
• Children under 6 months of age – 56 U/L.
• Babies from 6 months to one year – 54 units/l.
• Children from 1 to 3 years old – 33 units/l.
• Children from 3 to 6 years old – 29 units/l.
• Over 12 years – 39 U/L.
• Men – up to 45 U/L.
• Women – up to 34 U/L.

But often the results for ALT differ from the norm. This happens with inflammatory processes in the body, taking medications at the time of the test and due to a number of other factors. Also, unreliable results can be caused by intramuscular injections or increased physical activity.

There are three main stages of enzyme increase:

• Light – 1.5-5 times.
• Average – 6-10 times.
• Heavy – 10 times or more.

Increased alanine aminotransferase values are observed in the following liver diseases: hepatitis, cancer, cirrhosis, pancreatitis, myocarditis, myocardial infarction. The method of restoring normal enzyme levels depends on the causes that led to their change. In some cases, special medications are used to reduce ALT: Hefitol, Duphalac, Heptral. Also, all patients are prescribed a therapeutic diet.

AST

Aspartate aminotransferase (AST) is an enzyme of protein metabolism in the body. The substance is responsible for the synthesis of amino acids, which are part of tissues and cell membranes. At the same time, AST does not function in all organs, but it is present in liver tissue, heart muscle, neurons of the brain, and also in muscle tissue of skeletal muscles. The enzyme is involved in metabolic processes and helps maintain normal cell structure.

If the structure of cells with this enzyme is not damaged, then the amount of the substance is minimal and corresponds to the norm. Increased activity of aspartate aminotransferase indicates a narrow range of disorders. At the same time, there is a dependence: the more active the cytolysis (destruction of cells), the higher the AST values.

For analysis, venous blood is collected. The biological fluid is centrifuged, separating the plasma from the enzyme elements. The AST test is mandatory for the following somatic pathologies:

• Any liver disease or liver dysfunction.
• Poisoning and intoxication.
• Infectious diseases.
• Diseases of the circulatory system and heart.
• Kidney damage and renal failure.
• Purulent-septic conditions.
• Disorders of bilirubin metabolism.
• Autoimmune diseases.
• Ascites and portal hypertension.
• Endocrine disorders.
• Evaluation of the dynamics and effectiveness of treatment of the liver and heart.

When assessing the enzymatic activity of plasma relative to AST, the normal values of this substance are taken into account:

• Children – up to 50 IU
• Women – 34-35 IU
• Men – 40-41 IU

If AST does not exceed normal values in a liver function test or in a biochemical blood test, this indicates normal functioning of the liver and heart enzyme systems. Elevated values may indicate the following pathologies:

• Viral hepatitis (acute, chronic).
• Fatty and alcoholic hepatosis.
• Endogenous intoxications.
• Toxic liver damage.
• Cholestasis.
• Impaired hepatic blood flow and portal hypertension.
• Liver cirrhosis (decompensated form).
• Malignant metastases to the liver.
• Primary liver cancer.
• Cardiovascular disorders.

If the increase in AST differs from the norm by several units, this does not indicate pathology. An increase in the enzyme by two or more times has diagnostic value. Since the enzyme is contained in other organs in addition to hepatocytes, its isolated determination for assessing the state of the liver is not reliable. For this, AST is determined in relation to ALT. The study of two indicators more accurately reflects the state of the organ.

Bilirubin

A chemical compound and a product of the breakdown of red blood cells is bilirubin. The red-brown bile pigment is continuously produced in the body.

Types of bilirubin:

1. Total - all blood pigment circulating in the systemic bloodstream.
2. Indirect - part of the substance that is formed during the breakdown of red blood cells before they combine in the liver.
3. Direct - the part of the substance that binds to glucuronic acid and is excreted from the liver.

Initially, indirect bilirubin is formed in the blood and tissues, that is, a toxic compound that does not dissolve in water and is not excreted from the body. Together with the blood flow, it enters the liver, transforming into a direct form. The liver's task is to neutralize and bind bilirubin in the blood plasma, protecting the brain from the toxic effects of this substance.

Bilirubin metabolism norms for adults:

• Total – 8-20.5 µmol/l.
• Direct – 0-5.1 µmol/l.
• Indirect – 16.5 µmol/l.

Yellowing of the skin and mucous membranes is the main sign of a bilirubin metabolism disorder in the body. Headaches and dizziness, nausea, general deterioration and increased weakness are also possible. Such symptoms occur when the total bilirubin level is more than 50 μmol/l. The disease is called hyperbilirubinemia and has the following causes:

1. Increased direct bilirubin – cholangitis, obstructive jaundice, intrahepatic duct stones, biliary atresia, Mirizia syndrome, choledocholithiasis, tumor lesions, pancreatitis, pancreatic necrosis.
2. Increased indirect bilirubin – hemolytic jaundice or anemia, infectious diseases, intoxication, transfusion of incompatible blood, splenomegaly.
3. Hyperbilirubinemia due to both its fractions - parenchymatous and mixed jaundice, cirrhosis, cancerous tumors, hepatosis, hepatitis, congenital defects of bilirubin metabolism enzymes, pylephlebitis, sepsis.

The reasons for the change in the bilirubin norm may be related to any stage of its metabolism: output during the breakdown of red blood cells, liver dysfunction or excessive secretion of bile. The danger of such a condition is that the metabolic products are toxic to the body's tissues. An increase in the enzyme over 170 μmol/l is dangerous due to liver encephalopathy, renal and cardiovascular failure. Bilirubin over 300 μmol/l can cause death.

Treatment of elevated bilirubin levels depends on the causes that provoked hyperbilirubinemia. Patients are prescribed detoxification therapy, infusions, diuretics, hepatoprotectors, glucocorticoid hormones. In particularly severe cases, surgical intervention is performed.

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GGTP

Gamma-glutamyl transpeptidase is a protein of the liver and pancreas. GGT increases in diseases of these organs, as well as in alcohol abuse. The enzyme is a catalyst for biochemical reactions. It is not contained in the bloodstream, but is present only in cells, the destruction of which releases all the contents into the blood.

GGTP is a membrane-bound enzyme with high sensitivity. The main indications for the analysis are:

• Diagnosis of the condition of the liver, pancreas, bile ducts and bile ducts.
• Complaints of increased fatigue, loss of appetite, abdominal pain, nausea and vomiting.
• Monitoring the effectiveness of treatment for alcoholism and other diseases.

The protein allows to detect various pathologies at the earliest stages. The enzyme increases in such cases:

• Infectious hepatitis.
• Stagnation of bile secretion.
• Metastatic liver lesions.
• Diabetes.
• Diseases of the pancreas.
• Diseases of the cardiovascular system.
• Drug-induced liver degeneration.
• Hepatosis.
• Alcohol abuse.

In hypothyroidism, i.e. decreased thyroid function, GGTP is below normal. Compared to ALT, AST and alkaline phosphatase, the enzyme is more sensitive to disturbances in liver cells. Venous or capillary blood is used for the analysis.

Renal and liver function tests

Comprehensive diagnostics for identifying pathologies in the functioning of the kidneys and liver, as well as disorders in the work of other organs and systems - these are renal and hepatic tests.

Indications for analysis:

• Kidney and liver diseases of any severity and stage.
• Pain in the right hypochondrium and in the lumbar region.
• Deterioration of general well-being.
• Swelling of the face and lower extremities.
• Yellowing of the skin and mucous membranes.
• Endocrine disorders.

This profile of laboratory tests includes the following analyses:

• ALT
• AST
• GGTP
• Bilirubin (total, direct, indirect)
• FS
• Total protein
• Albumen
• Uric acid
• Creatinine
• Urea

Basic metabolite substances reflecting kidney function:

1. Creatinine – takes part in cellular energy exchange in muscle tissue. It is released from myocytes, then transported to the kidneys and excreted in urine. When the kidneys are damaged, creatinine excretion decreases, as it accumulates in the blood. A change in the level of this substance may indicate acute inflammation.
2. Urea is a product of protein breakdown. It indicates the excretory capacity of the kidneys. Deviations from the norm most often indicate chronic diseases.
3. Uric acid – occurs during the breakdown of complex nucleotides and is completely excreted in the urine. An increase in this indicator is observed in acute renal failure.

When evaluating the test results, not only the indicators of renal and hepatic tests are taken into account, but also the general condition of the body and the presence of clinical symptoms.

Liver function tests by urine

The liver performs many functions that support the normal functioning of the entire body. It is responsible for filtering and removing toxic substances. A change in the color of urine in combination with pain in the right hypochondrium indicates problems with the functioning of the organ.

To diagnose the disease, a set of laboratory and instrumental studies is carried out. Particular attention is paid to liver tests in urine. Urine is tested for the presence of bile segments: bilirubin, urobilinogen. They are not found in a healthy body.

Urobilinogen and urobilin

These are important bile enzymes that can be detected in urine analysis. They simplify the process of diagnosing various pathologies associated with the liver, bile ducts and bladder, and the hematopoietic system. This indicator is additional, although it is included in the general urine analysis.

Urobilinogen is an enzyme that is formed after the breakdown of bilirubin. Together with bile, it enters the intestine, part of it is absorbed into the blood and goes back to the liver tissue, and the rest is excreted with urine. The enzyme is always present in the analysis, but its values are small - 5-10 mg / l. An increased level or absence of this substance are deviations from the norm.

The urobilinogen test has the following indications:

• Urination disorders – frequent or rare urge to go to the toilet, pain and cramps in the abdomen.
• Nausea and vomiting, yellowing of the skin.
• Urine is dark in color.

Elevated values indicate liver disorders that can be caused by various pathologies: cirrhosis, hepatitis, intoxication, spleen damage, enterocolitis. In some cases, deviations from the norm occur due to physiological factors.

Normalization of the enzyme consists of restoring healthy liver function and normal bilirubin levels. Treatment depends on the severity of the disease. Patients may be prescribed hepatoprotectors, choleretic drugs, and dietary nutrition. Diagnostics of liver function tests are performed on the basis of a fresh morning portion of urine. A blood test is required for a more accurate determination of enzyme levels.