What are the normal ranges for liver enzymes. How are GGT tests performed. What do high GGT levels indicate. What are the symptoms of liver damage. What conditions can cause liver damage. How is GGT used to diagnose alcohol use disorder.

The Importance of Gamma-Glutamyl Transferase (GGT) in Liver Health Assessment

Gamma-glutamyl transferase (GGT) is a crucial enzyme that plays a significant role in diagnosing liver problems. Healthcare professionals rely on GGT tests to evaluate liver function and detect potential issues within the liver or bile ducts. Understanding the normal range of GGT levels is essential for interpreting test results and identifying potential health concerns.

The typical range for GGT levels in adults and children is between 0 and 30 international units per liter (IU/L). When GGT falls within this range, it generally suggests that there is no liver damage present. However, it’s important to note that newborn infants naturally have significantly higher levels of GGT immediately after birth.

Why do doctors order GGT tests?

Doctors may request a GGT test for various reasons, including:

• As part of routine blood testing or physical examinations
• To monitor patients taking medications with potentially toxic effects on the liver
• When a person exhibits symptoms of liver disease
• To track the progress of treatment for individuals with alcohol use disorder

The GGT Test Procedure: What to Expect

The GGT test is a straightforward blood test that typically takes less than 5 minutes to complete. During the procedure, a healthcare professional will:

1. Tie a band around the upper arm
2. Clean the inner elbow thoroughly with an alcohol pad
3. Insert a small needle into the skin
4. Collect a small tube of blood
5. Remove the needle and band
6. Apply pressure to the site to stop any bleeding

While the blood draw may cause minor discomfort, this sensation usually passes quickly. After collection, the sample is labeled and sent to a laboratory for analysis. Results are typically available within a day or two, although it may take slightly longer for the doctor to receive and interpret the findings.

Are there any special preparations required for a GGT test?

In most cases, no special preparations are necessary for a GGT test. However, some doctors may advise patients to fast for at least 8 hours before the test. It’s important to note that GGT levels are highly sensitive and can be temporarily elevated by certain medications or alcohol consumption. For this reason, healthcare providers may recommend avoiding these substances for 24 hours before the test.

Interpreting GGT Test Results: High, Low, and Normal Ranges

Understanding GGT test results is crucial for assessing liver health. Here’s a breakdown of what different GGT levels may indicate:

Normal GGT Levels

A GGT level within the typical range of 0-30 IU/L is generally not a cause for concern. It suggests that the liver is functioning normally and there is likely no significant liver disease present.

Elevated GGT Levels

High levels of GGT in the blood could indicate that the enzyme is leaking out of liver cells and into the bloodstream. This may suggest damage to the liver or bile ducts. The extent of the elevation often correlates with the degree of liver damage.

It’s important to note that while elevated GGT levels can indicate liver damage, they do not diagnose the specific cause. Additional tests are usually required to determine the underlying reason for the increased GGT levels.

Recognizing Symptoms of Liver Damage

Liver disease can manifest with a range of symptoms that vary in severity. Some common signs of liver damage include:

• Jaundice (yellowing of the skin, eyes, or mucous membranes)
• Dark urine
• Nausea and vomiting
• Abdominal pain
• Light-colored stools

When should you be concerned about these symptoms?

If you experience any of these symptoms, especially in combination with elevated GGT levels, it’s crucial to consult with a healthcare professional promptly. Early detection and intervention can significantly improve outcomes in liver disease.

Common Causes of Liver Damage and Elevated GGT Levels

Several conditions can lead to liver damage and subsequent elevation of GGT levels. Some of these include:

• Hepatitis (viral or autoimmune)
• Cirrhosis
• Diabetes
• Pancreatitis
• Congestive heart failure
• Exposure to toxins
• Certain medications
• Alcohol use disorder

How does alcohol consumption affect GGT levels?

GGT levels tend to be higher in individuals who regularly consume alcohol compared to those who drink in moderation or occasionally. This sensitivity to alcohol makes GGT a valuable marker for detecting and monitoring alcohol use disorder.

GGT in Conjunction with Other Liver Function Tests

While GGT is a sensitive indicator of liver health, it is often used in combination with other liver function tests to provide a more comprehensive assessment. These additional tests may include:

• Alanine aminotransferase (ALT)
• Aspartate aminotransferase (AST)
• Alkaline phosphatase (ALP)
• Bilirubin
• Protein levels

How does GGT help differentiate between liver and bone disorders?

GGT can be particularly useful in distinguishing between liver or bile duct diseases and bone disorders when used in conjunction with alkaline phosphatase (ALP) testing. Both liver disease and bone conditions can lead to elevated ALP levels. However, a normal GGT level in the presence of high ALP may indicate a bone issue, while elevated levels of both enzymes suggest a problem with the liver or bile ducts.

The Role of GGT in Diagnosing Bile Duct Injuries

GGT is a valuable marker for detecting bile duct injuries. Levels of this enzyme typically rise when a person has a bile duct obstruction. The sensitivity of GGT to bile duct issues makes it an essential component of comprehensive liver health assessments.

What other conditions can cause elevated GGT levels?

While liver and bile duct problems are common causes of high GGT, other factors can influence levels as well. These may include:

• Certain medications
• Smoking
• Obesity
• Diabetes
• Pancreatic diseases

Given the multiple factors that can affect GGT levels, healthcare providers often consider the results in context with other clinical findings and additional tests to make accurate diagnoses.

GGT and Alcohol Use Disorder: A Valuable Diagnostic Tool

The relationship between GGT levels and alcohol consumption makes this enzyme test particularly useful in diagnosing and monitoring alcohol use disorder. Regular alcohol consumption tends to elevate GGT levels more significantly than occasional or moderate drinking.

How can GGT tests help in managing alcohol use disorder?

Healthcare providers may use GGT tests to:

• Screen for potential alcohol abuse
• Monitor treatment progress in individuals with alcohol use disorder
• Assess the effectiveness of alcohol cessation programs
• Detect relapse in recovering alcoholics

Regular GGT testing can provide valuable insights into a patient’s alcohol consumption patterns and help guide treatment strategies.

The Limitations of GGT Testing

While GGT is a sensitive marker for liver and bile duct health, it’s important to understand its limitations. GGT elevation alone cannot diagnose specific liver conditions or determine the exact cause of liver damage. Therefore, healthcare providers typically use GGT results in conjunction with other liver function tests, clinical symptoms, and patient history to make accurate diagnoses.

When might false-positive or false-negative GGT results occur?

Several factors can influence GGT levels and potentially lead to misleading results:

• Certain medications
• Recent alcohol consumption
• Smoking
• Pregnancy
• Obesity

Healthcare providers consider these factors when interpreting GGT test results to avoid misdiagnosis.

Lifestyle Modifications to Improve Liver Health and GGT Levels

For individuals with elevated GGT levels or those at risk of liver disease, certain lifestyle changes can help improve liver health and potentially lower GGT levels:

• Limiting alcohol consumption or abstaining completely
• Maintaining a healthy diet rich in fruits, vegetables, and whole grains
• Exercising regularly to maintain a healthy weight
• Avoiding exposure to toxins and chemicals
• Managing underlying conditions such as diabetes or obesity

How quickly can lifestyle changes affect GGT levels?

The impact of lifestyle modifications on GGT levels can vary depending on the individual and the underlying cause of elevation. Some people may see improvements within weeks, while others may require several months of consistent healthy habits to notice significant changes. Regular monitoring with healthcare providers can help track progress and adjust strategies as needed.

The Future of Liver Health Assessment: Emerging Technologies and Biomarkers

While GGT remains a valuable tool in liver health assessment, researchers continue to explore new technologies and biomarkers to enhance diagnostic accuracy and provide more comprehensive insights into liver function.

What new liver function tests are being developed?

Some emerging areas of research in liver health assessment include:

• Non-invasive imaging techniques for liver fibrosis detection
• Genetic markers for predicting liver disease susceptibility
• Advanced proteomics for identifying novel liver-specific biomarkers
• Artificial intelligence-assisted interpretation of liver function test results

These advancements may complement existing tests like GGT, providing more precise and personalized liver health assessments in the future.

Understanding the significance of GGT levels and their role in liver health assessment is crucial for both healthcare providers and patients. By recognizing the importance of this enzyme test, individuals can take proactive steps to maintain liver health and seek timely medical attention when necessary. As research continues to advance our understanding of liver function and disease, GGT testing remains an essential tool in the broader landscape of hepatic health evaluation.

Normal ranges, uses, results & what to expect

Doctors use the gamma-glutamyl transferase (GGT) test to diagnose liver problems. A typical range for GGT levels in adults and children is between 0 and 30 international units per liter.

In the GGT test, a healthcare professional measures the levels of GGT in a sample of blood. High levels of GGT can indicate damage to the liver or bile ducts. When GGT falls within the typical range, it suggests that there is no liver damage.

A GGT test cannot diagnose the cause of any liver problems, so doctors usually also request other liver blood tests, such as an alkaline phosphatase (ALP) test. ALP is another liver enzyme that doctors use to help diagnose bone disorders in addition to liver disease.

A doctor may order a GGT test for the following reasons:

• part of regular blood testing or physical examination
• if a person is taking a medication that has potentially toxic effects on the liver
• if a person has symptoms of liver disease
• monitoring the treatment of people with alcohol use disorder

Read on to learn more about the GGT test including its purpose, procedure, and what abnormal GGT ranges can mean.

The test should take less than 5 minutes. During the test, the healthcare professional ties a band around the upper arm, cleans the inner elbow thoroughly with an alcohol pad, and inserts a small needle into the skin. They then collect a small tube of blood.

After the test is complete, the healthcare professional will remove the needle and the band. They will also apply pressure to the site to make sure any bleeding stops.

As with any other blood test, the blood draw may cause minor discomfort. This pain should pass quickly.

The healthcare professional labels the sample and sends it to a lab for testing. The lab should produce the results within a day or two, though it may take a little longer for the doctor to receive and interpret the results.

Typically, a person does not need any special preparations for a GGT test.

In some cases, the doctor may ask the person to fast for at least 8 hours before.

GGT is very sensitive and may temporarily elevate if the person takes certain medications or drinks alcohol. The doctor may ask the person to avoid these 24 hours before testing the GGT levels.

A typical range for GGT levels in adults and children is between 0 and 30 international units per liter (IU/L). Newborn infants have significantly higher levels of GGT right after birth.

Typical GGT levels are not concerning to a doctor. A person with a GGT level within the expected range probably does not have liver disease.

The liver contains the highest levels of GGT, while the blood and some other organs contain minimal quantities.

High levels of GGT in the blood could indicate that the enzyme is leaking out of the liver cells and into the blood. This may suggest that there is damage to the liver or bile ducts. GGT levels rise according to the amount of liver damage a person has.

High GGT levels could indicate liver damage, though it does not diagnose the specific cause. A person often needs follow-up tests to determine the reasons for the elevated GGT levels.

Symptoms of liver damage

The symptoms of liver disease can range in severity. Some symptoms of liver damage include:

• jaundice, which causes yellow skin, eyes, or mucous membranes
• dark urine
• nausea
• vomiting
• abdominal pain
• light-colored stool

Causes of liver damage

Some conditions that can cause liver damage include:

• hepatitis
• cirrhosis
• diabetes
• pancreatitis
• congestive heart failure
• exposure to toxins
• some medications
• alcohol use disorder

GGT levels may increase for many reasons. A doctor may request other tests in conjunction with a GGT test to diagnose liver disease.

Liver or bile duct damage

GGT is a useful marker for detecting bile duct injury. GGT levels usually rise when a person has a bile duct obstruction.

It is a very sensitive liver enzyme test. The GGT test is also part of a series of tests known as a liver panel or liver blood tests, which check the levels of other liver enzymes.

Other liver enzyme levels that doctors check are alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP). This panel of blood tests can also check the levels of proteins, and bilirubin, a waste product of the liver.

Someone with an elevated ALP level may need a GGT test to narrow down the cause.

Bone disease and liver or bile duct disease can lead to elevated ALP levels. A GGT test can help distinguish between these disease types: a typical GGT level likely indicates a bone issue, while a high GGT level may signal a problem with the liver or bile ducts.

Alcohol use disorder

GGT levels tend to be higher in people who regularly drink alcohol, compared with people who drink in moderation or only on occasion. Because of this, a doctor may measure GGT levels to test for alcohol use disorder.

Doctors may use the test to monitor alcohol use in someone receiving treatment for alcohol use disorder or hepatitis due to chronic alcohol use.

Having a blood test is a very safe procedure.

Some people may experience bruising at the needle insertion site after the test. It is also normal to feel a little sore for a short time after the test.

Occasionally, a person may feel faint or anxious during the test, causing them to blackout or pass out. Though this can be frightening, it does not indicate a serious reaction.

Overall, a person’s outlook can depend on the causes of elevated GGT levels.

Doctors can treat the underlying cause of liver disease and prevent further damage to the liver with medication. They might also recommend that people avoid alcohol and certain drugs (both illegal and prescription). If the doctor suspects liver failure, they can consider a transplant.

Learn more about liver disease, including treatment options and prognosis here.

Gamma-glutamyl transferase test (GGT) is a blood test that a doctor may order to assess damage to the liver or bile ducts. However, because this test cannot diagnose the underlying cause, GGT normally form part of a series of tests to help with diagnosing certain diseases.

A typical range for GGT is 0–30 IU/L, although newborn babies may have significantly higher levels.

Individuals may have raised GGT because of:

• liver damage
• alcohol use disorder
• diabetes
• liver problems
• congestive heart failure
• side effects of some medications.

If a person has high GGT results, their doctor typically orders additional testing.

High and low levels, and what do results mean

An AST blood test measures levels of aspartate aminotransferase (AST) and helps determine liver function. Too much of this enzyme can indicate a problem, such as liver damage.

Aspartate aminotransferase (AST) is an enzyme mostly found in the liver. AST is also present in other parts of the body, including the:

• kidneys
• heart
• muscles

Another name for the AST enzyme is serum glutamic-oxaloacetic transaminase (SGOT).

Most people have low levels of the AST enzyme. Damage to liver cells can cause the release of extra AST into the blood though, leading to higher levels of the enzyme.

After taking a blood test, doctors will classify AST ranges as normal, high, or low. Laboratories may use different testing methods for analyzing samples, so normal ranges can vary between each laboratory.

There is not an exact range for AST levels, as levels can vary among people and still be normal. AST levels can vary depending on factors such as:

• age
• sex
• weight
• race

The measurements for AST levels are typically in units per liter (U/L) or international units per liter (IU/L). On a test result, the laboratory will usually list their specific reference range.

People will need to look at this reference range and discuss with their doctor what their test results mean for them. To understand the results of an AST blood test, a doctor will also look at other enzymes that can indicate a liver problem.

The following table indicates general AST blood test ranges. However, reference ranges can vary slightly among different laboratories.

Results from an AST blood test can help indicate liver health.

If AST levels are high, it may also be a sign of:

• chronic hepatitis
• damage from alcohol
• cholestasis, a decrease in bile flow
• heart, kidney, bone, or muscle damage
• liver cancers
• liver scarring, known as liver cirrhosis

Very high AST levels are usually a sign of progressing liver damage, often due to acute hepatitis.

Low AST levels may indicate:

• vitamin B6 deficiency
• kidney disease
• liver disease
• cirrhosis
• cancer
• autoimmune conditions
• genetic conditions

A doctor may also test levels of alanine aminotransferase (ALT), another liver enzyme. ALT levels occur in higher concentrations in the liver.

If ALT levels are normal but AST levels are high, it could indicate a health problem outside of the liver, or it may be a sign of alcohol-induced liver damage.

Having high levels of AST and no other signs of a problem is not necessarily a cause for concern. People with normal liver function can have high AST levels, which may be due to:

• age
• sex
• race
• certain medications

A person should always discuss any medications or health products they take with a doctor.

Doctors primarily use the AST blood test to check for and assess liver problems, usually alongside other liver tests. The AST protein mainly occurs in the liver and heart. With liver damage, AST can leak from the liver into the bloodstream. When this happens, AST levels in the blood will be higher than normal.

AST also occurs in the brain, heart, kidneys, and muscles. If there is damage in any of these areas, AST levels may also increase.

To rule out issues affecting areas outside the liver, doctors may order a check of the second liver enzyme, ALT, at the same time. If both levels are high, it may indicate a problem with a person’s liver. If only AST levels are high, this may indicate a problem with another organ or system.

People may have an AST test for screening, diagnosis, or monitoring purposes. A doctor may recommend this test if a person:

• has risk factors for liver disease, such as family history, obesity, or diabetes
• has symptoms of a liver problem, such as jaundice, fatigue, or unexplained weight loss
• is undergoing treatment for a liver condition, as an AST blood test can help show how well treatment is working

Alanine aminotransferase (ALT) is an enzyme that mostly occurs in the liver. If there is damage to liver cells, ALT levels in the bloodstream can increase. An ALT test can help indicate liver health, along with other liver enzyme tests.

Healthcare professionals may use both ALT and AST tests to check for the presence of liver enzymes in the blood, as this can give them a clearer idea of overall liver function and health.

Learn more about the ALT test here.

The AST blood test is straightforward and similar to any other blood test. A healthcare professional may take the following steps:

• sit the person down and tie a stretchy band around the upper arm to increase blood flow to that area
• clean the site of the blood draw with an antiseptic wipe
• insert a needle into a vein in the arm to take a blood sample, which may cause people to feel a mild prick or pain
• remove the needle once they have drawn enough blood
• send the blood sample to a laboratory for testing

An AST blood test will usually only take a few minutes in total.

In some cases, people may be able to take an AST test at home. Using an at-home test kit, people will take a blood sample from their fingertip and send the sample to a laboratory. People may receive AST blood test results through the mail, an app, or an online system.

Learn how long it might take to receive blood test results here.

Preparation

People may need to fast for several hours if they are having a combination of liver enzyme tests.

If people are only having an AST blood test, they may not need to fast or prepare in any way.

People will need to let their doctor know if they are taking any medications or supplements, as some may interfere with liver enzyme levels.

As a healthcare professional will be taking blood from the arm, it may be helpful to wear short sleeves during the test.

As with any blood test, an AST blood test has very few risks. It is rare to experience any severe side effects, but people may have some mild bruising or discomfort in the area at the site of the blood draw.

A healthcare professional will place a Band-Aid or bandage on the arm to stop any bleeding.

People may want to have something to eat after the test, particularly if they were fasting beforehand. It is safe for people to drive and continue their usual activities after an AST blood test, unless they experience any unusual symptoms.

A doctor may order tests along with an AST blood test or follow-up tests. This is to help ensure proper diagnosis and determine the best course of treatment. These tests may include:

• ALT test: A doctor may order an ALT test alongside an AST test.
• Platelet count: Low platelet levels may indicate HELLP syndrome during pregnancy.
• Coagulation panel: This measures the functioning of clotting-related proteins that the liver produces.
• Complete metabolic panel: This assesses how well the kidneys and liver are working and shows levels of electrolytes.
• Bilirubin test: A bilirubin test checks levels of a byproduct created when the liver breaks down red blood cells.
• Glucose test: High or low blood glucose levels may indicate a liver problem.
• Viral testing: This can help doctors check for hepatitis.
• Imaging: A doctor may order images of the liver via ultrasound.

The extent of follow-up testing will depend on a person’s results. A doctor may also take additional blood tests, imaging tests, or a biopsy to identify or rule out any potential conditions relating to abnormal AST levels.

Learn about different types of blood tests here.

An AST blood test, or SGOT test, checks how much AST, a liver enzyme, is present in the blood. High levels of AST in the bloodstream could be a sign of liver damage, or cell damage in another organ such as the heart or kidneys.

Doctors may also take additional tests to check other liver enzymes, such as ALT, to get more information on the health of the liver.

Norms of analyzes. Analysis decoding. Reference values, interval. “Norm” and “pathology” in laboratory diagnostics.

This article describes what test norms are, how tests are deciphered, why it is not modern to say “norm”, and what are reference values ​​​​and reference intervals.

Standards for interpretation of tests.

Concept of reference values ​​and reference interval.

The information obtained in the course of laboratory analysis is based on the detection and / or measurement in clinical samples (biomaterial) of patients of certain components – analytes, functionally or structurally related to a specific human organ or organ system. The most important component of any laboratory research is the interpretation of its result. Establishing the difference between the norm of analyzes and pathology plays a key role in assessing the data obtained. In practice, this is not difficult to do with a clear deviation of laboratory parameters from the values ​​taken as the norm. However, it is not always easy to divide most of the results of laboratory tests into “normal” and “pathology”, and therefore, in order to interpret them, a comparison of the data obtained with the indicators established as the norm is required.

Normal test values ​​(norm) are values ​​found in healthy people. However, in the groups of the latter, they can have different values, that is, the norm is individual. This is due both to the individual physiological characteristics of the human body (characteristics of metabolism, circadian biological rhythms, the functional state of certain organs and their systems), and differences in gender, age, and physiological state. For example, during pregnancy, many biochemical parameters of a woman’s body change, therefore, appropriate individual norms are determined for pregnant women.

Normal laboratory values ​​are determined in experimental clinical studies based on the results of measurements of the analyte under investigation in a large population of healthy people, specially selected and grouped by age, sex or other biological and other factors. The data obtained lead to the mean value, taking into account the statistically possible standard deviations of its value. In this regard, it is more correct to speak not about the “norm” of a laboratory indicator, but about the range in which normal (reference) values ​​are located. Therefore, at present, the term “norm”, which has already become familiar in assessing the results of a laboratory study, is used less frequently. Instead, they talk about reference (reference) values ​​ and the results obtained for a particular patient are compared with the so-called reference interval (range) . This term is more accurate, because it gives an idea of ​​the lower and upper limits of the norm of a laboratory indicator, possible, statistically significant limits of fluctuation (deviation) of its value and, at the same time, emphasizes the relativity of these data, the possibility of applying only to a certain group of people.

Explanation of analyzes. Norm or pathology?

When establishing the reference range, mathematical and statistical approaches are used, according to which the values ​​of the results of laboratory studies of a certain analyte of 95% of healthy people fall within the established interval. Accordingly, for 5% – the values ​​of the analyzed indicators are outside the established range. In other words, in 5% of cases in healthy people, “abnormal” laboratory parameters are detected, which should be taken into account when deciphering the analysis. This is explained by a number of reasons.

First, the division of the biological population of people into “sick” and “healthy” according to many laboratory parameters is very conditional. Being statistical data, the limits of normal laboratory values ​​may vary. Therefore, it happens that in healthy people certain indicators that are “normal” for them are not ultimately “normal” for most others, and therefore do not fall into the range of generally accepted reference values. In this case, the limits of the reference range cannot serve as absolute indicators of health or disease.

On the other hand, often the disease develops imperceptibly, manifesting itself as a gradual transition from small deviations in the values ​​of laboratory parameters to their higher values ​​as dysfunction increases and the severity of the disease progresses. In this regard, when deciphering the analyzes in interpreting the results of laboratory tests, it becomes very important for the clinician to assess the dynamics of changes in a particular laboratory indicator in a particular patient. In doubtful cases, the main criterion for the presence or absence of a disease is the clinical symptomatology or the degree of its severity. In the presence of symptoms of the disease, additional laboratory tests are used for diagnosis using highly sensitive and specific tests that most pronouncedly change their values ​​against the background of the suspected disease.

Secondly, “healthy” and “sick” people actually belong to two different populations, and when these populations are mixed together, it is almost impossible to recognize each of them in the total mass. In addition, in different patients, the same indicator can not only take on different values, but also overlap the values ​​of this indicator in healthy people. Moreover, for different indicators, different diseases, different groups of patients, the value of such a “crossover” can vary greatly: from too small, which can be neglected, to very significant, when a special approach and careful analysis of all data is required to classify the result as “normal” or “pathological”. The latter is extremely important to take into account when evaluating the results of laboratory tests, since in this case not all values ​​that are outside the normal range will indicate the presence of pathology. The range of values ​​in which the laboratory parameters of “sick” and “healthy” individuals overlap is called the zone of uncertainty, or the “gray zone”. It exists for a range of laboratory procedures, but is most commonly found in enzyme immunoassay results. If the result falls into the “gray zone”, it cannot be unequivocally regarded either as a norm or as a pathology and is considered as doubtful. In such a case, the patient is usually advised to repeat the diagnostic study 2 to 4 weeks after receiving an indeterminate result.

And, finally, not always an indicator lying in the reference interval can be considered normal, since the range of many of them is quite wide. For example, the normal value of hematocrit (Ht) in men varies from 42 to 52%. Massive blood loss can lead to a drop in this indicator from 52 to 42%, while the value of 42% remains within the range of reference values, and therefore may not cause alarm for doctors. However, in a certain situation, for a particular patient, such a decrease in hematocrit can be not only clinically significant, but also critical.

Therefore, results within the reference range are not always normal. And, on the contrary, the results that go beyond the reference values ​​are not always pathology, but only a significant prognostic sign that can signal a possible pathological process. In this regard, in laboratory diagnostics, the approach is becoming more widespread, when the most significant and adequate reference values ​​for each individual patient should be considered stable results of his laboratory studies obtained over several years. Already at present, experts around the world are inclined to believe that it is necessary to “lower” the significance of reference intervals, moving away from interpreting them as some kind of “absolute” criterion for evaluating a laboratory result. This circumstance in no way reduces the importance of laboratory research. They remain the most important tool for diagnosing pathological conditions, monitoring the course of diseases, identifying the preclinical stage of diseases during screening examinations, and also largely determine the further tactics of diagnostic procedures and treatment decisions. However, this approach directs the clinician to a more cautious use of reference values ​​in the assessment of “normal” and “pathological” results, indicating the need for their interpretation, taking into account possible biological variation in the population, taking into account the data of the clinical picture and other types of studies in the aggregate, and as well as those factors that may influence the results of laboratory tests.

Reference ranges

Reference values ​​are currently established for many laboratory parameters. The results of some types of research are given to the patient in the form of “yes” or “no”. This type of research is qualitative. For example, a positive result for antibodies to a specific infection indicates the presence of these antibodies in the patient’s blood and may indicate infection. In the case when the study was quantitative, the result is issued as a numerical value, indicating on the form the units of measurement and the corresponding reference range. For example, the results of a biochemical study to determine the level of C-reactive protein (CRP), which is a marker of inflammation, may look like this: 0.4 mg / l, reference values: 0 – 6 mg / l. From the above example, it can be seen that the result obtained is within the established reference range. For most laboratory parameters, the range of reference values ​​is indicated taking into account the patient’s gender and / or his belonging to a certain age group. For example, the reference values ​​​​of serum creatinine for children under 1 year old are 18 – 35 µmol / l, for children from one to 14 years old – 27 – 62 µmol / l, and for people over 14 years old – 62 – 115 µmol / l for male and 53 – 97 µmol/l for females.

The influence of age and sex on the range of reference values ​​is significant for many laboratory tests. For example, the concentration of alkaline phosphatase, a key enzyme secreted by bone tissue cells, increases in proportion to the rate of formation of new bone cells. Therefore, in children and adolescents, a high level of this enzyme is not only normal, but also desirable, since it is associated with the active formation and growth of bones. On the contrary, a high level of alkaline phosphatase in an adult may indicate developing osteoporosis, metastases of bone tumors, or other pathological processes. The exception is pregnant women, who are characterized by a physiological increase in the activity of this enzyme, especially in the third trimester of pregnancy.

Why can reference ranges differ from laboratory to laboratory?

Different diagnostic laboratories use different types of laboratory equipment to perform analysis, for example, biochemical and immunochemical analyzers, the range of which is currently very wide, work with reagents from different manufacturers, and in addition, they may use different research methods than other laboratories . In this regard, each laboratory indicates on the form of results its ranges of reference values, when establishing which, of course, it is guided by generally accepted standards, but taking into account the individual characteristics of its work: the specifics of the equipment used, the methods of analysis used and units of measurement. That is why the ranges of reference values ​​for the same laboratory test may vary according to the data of different diagnostic laboratories, and there is no such thing as a “single” reference range. When evaluating the results of laboratory tests, the attending physician should first of all refer to the range of reference values ​​indicated on the form of the laboratory in which the analysis was performed. In order for the results to be interpreted correctly and comparable, especially in the case of repeated studies, for example, when monitoring therapy or dynamic assessment of the patient’s condition, it is advisable to conduct studies using the same method, in the same laboratory and, if possible, ceteris paribus.

Factors affecting laboratory results

Modern methods of clinical laboratory research are characterized by high sensitivity and specificity, and therefore their results, reflecting the patient’s health, can serve as the basis for making important clinical decisions by the attending physician. At the same time, both clinicians and patients should understand that there are a number of non-pathological factors that can, to a certain extent, influence the results of laboratory tests, distorting the objective picture of the patient’s health. Some of these factors can only be controlled by the efforts of laboratory specialists, minimizing their possible negative impact on the final result of the laboratory study. Among such factors, for example, the conditions and method of taking biological material, delivery and storage of samples, the correctness of their identification in the laboratory. However, to minimize the negative impact of many other factors that affect the accuracy of the final result of a laboratory test, only the patient himself or his attending physician, who must inform the patient about the correct preparation for a certain type of laboratory test, can. Compliance with the doctor’s instructions will allow the analysis to be as close as possible to the general requirements, for example, the need to donate blood on an empty stomach, and thereby bring the results of the study as close as possible to the reference ones for this group of patients.

What factors can influence the results of laboratory tests? First of all, it should be noted the sensitivity of many laboratory tests to the time interval associated with the patient’s intake of food in general or individual products in particular, as well as the peculiarities of his eating behavior, for example, diet (meat or vegetarian), coffee and alcohol consumption. For example, high blood sugar may be related to a recent meal rather than diabetes. Eating shortly before the study will affect the results of lipid profile tests, insulin and C-peptide levels. In this regard, in order to obtain accurate results of the study, it is recommended to donate blood in the morning on an empty stomach, usually not less than 8 and not more than 14 hours after the last meal. On the eve of the study, food overload should be avoided.

High levels of liver enzymes may be due to recent or frequent alcohol use. Caffeine can cause an increase in the concentration of catecholamines and renin in plasma. Smoking sometimes causes a borderline increase in the level of some tumor markers.

Lab test results may be affected by vitamin and nutritional supplements and medications. In this case, the effect of drugs can be multidirectional. They can not only change the physiological processes in the body, but also chemically interfere (interact) with the analyzed analyte under conditions in vitro . An example of the effect of drugs on the physiological level is the increase in liver enzymes under the influence of hepatotoxic drugs. Drugs that affect plasma volume can cause changes in the concentration of proteins, urea nitrogen, iron and calcium. An example of another influence is non-specific binding reactions of certain drug metabolites with individual components of the reaction mixture, for example, polyclonal antibodies in immunoassays, as a result of which an erroneous result can be obtained. In this regard, a patient taking any medications should consult with a doctor about the advisability of conducting a laboratory study while taking medications or the possibility of stopping them before the study.

Among the factors affecting the results of laboratory tests is physical activity. Physical stress leads to a volumetric shift between the vascular bed and the intercellular space, loss of fluid with sweat and, as a result, to a change in the concentration of some analytes: hormones or enzymes. Therefore, visiting, for example, a gym on the eve of a laboratory test is undesirable. Heavy physical activity can cause an increase in the level of certain enzymes (ALT, AST, LDH, creatine kinase), a change in the level of various blood substrates (glucose, urea, etc.), and increase the excretion of protein in the urine. In addition, people who have been actively involved in sports for a long time, such as long-distance running or weightlifting, may have slightly increased levels of testosterone and luteinizing hormone (LH).

A general recommendation to prepare for the test is to rest (preferably sit) for 10 to 20 minutes after arriving at the laboratory before taking blood samples. This is also due to the fact that the results of some laboratory tests can be influenced by the body position of the subject at the time of its conduct, as well as the emotional state of the person before and during the study. So, for example, a change in body position from a lying position to a sitting or standing position causes vasoconstriction, and a change in position from a sitting to a lying position causes a shift of water and electrolytes in the tissue, leading to blood concentration. As a result, serum or plasma levels of total protein, albumin, lipids, iron and calcium change upward.

Emotional stress can cause significant increases in cortisol, ACTH and glucose levels. Among other things, stress is combined with an increase in the concentrations of albumin, fibrinogen, insulin, lactate and cholesterol. That is why it is so important, if possible, to exclude psycho-emotional stress on the eve of the study and try not to worry in the process of taking a biological sample.

Temporary changes in some laboratory parameters may be caused by physiotherapy and instrumental examinations (eg, prostate biopsy before PSA testing). In such cases, it is recommended to postpone the laboratory examination for several days.

For a number of hormonal studies, it is important to take into account the phase of the menstrual cycle in women, and therefore you should check with your doctor in advance the optimal days for blood donation to determine the level of FSH, LH, inhibin B, prolactin, progesterone, estradiol and some other hormones.

Time of day during sampling is especially important when cortisol, thyroid stimulating hormone (TSH), and certain other analytes are needed. At the same time, it should be borne in mind that the reference values ​​- the boundaries of the “normal” laboratory parameters, usually reflect the statistical data obtained under standard conditions when taking blood in the morning.

Thus, there are a number of reasons why the results of the analysis may fall outside the established range of reference values, even if the person is absolutely healthy. Therefore, if the patient is aware of any special circumstances that could affect the results of the studies, they should be reported to their doctor. Don’t expect him to figure them out on his own. After all, a result that does not correspond to the “norm” is not necessarily a sign of a disease, and therefore the doctor needs to understand its possible cause. It is possible that this is just the case when the result obtained falls into those very statistically significant 5%, in which the laboratory parameters of healthy people are outside the reference range. Sometimes some “abnormal” results can go back to normal on their own, especially if they were on the border of the reference values. In addition, there are not many diseases that can be diagnosed with just one single test.

The above examples show that in order to adequately evaluate the results of laboratory tests, as well as to make the right clinical decisions for the patient on the basis of them, a comprehensive approach is needed that takes into account all the variety of factors that can affect the accuracy and correctness of the data obtained. . Clinical conclusions and decisions based on the results of laboratory analyzes will be correct only if the various preanalytical and analytical factors are sufficiently standardized and fully taken into account. It is very important that the patient be able to follow all the necessary recommendations for preparing for laboratory tests, and the attending physician, interpreting the data obtained, would take into account the possible impact on the result of the study of non-pathological factors that occurred, and also comprehensively evaluate the results, taking into account the clinical picture and data from other types research.

Laboratory diagnostics specialists, if necessary, are always ready to answer questions on the results obtained, provide additional special information and explanations or consult in complex cases.

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How to decipher a biochemical blood test: the norm of indicators

Likbez

Health

November 11, 2020

This is a quick way to check your liver, kidneys, blood sugar and metabolic quality.

Why do we need a biochemical blood test

The meaning of a biochemical blood test (BAC) can be explained in a nutshell. If a general blood test (CBC) gives an idea of ​​the state of the body as a whole, then the BAC adds details – it tells whether specific organs and systems are healthy.

A biochemical blood test helps detect liver, kidney, diabetes and other ailments.

In addition, the LHC allows you to find out if everything is in order with the level of sugar in the blood, metabolism and what important vitamins, micro and macro elements, hormones, enzymes the body lacks for normal functioning.

What your blood chemistry shows

The technician will take a few milliliters of blood from your vein. This must be done on an empty stomach – 8-12 hours after the last meal. The sample taken is then examined for several key components. They are divided into groups.

Glucose

Or blood sugar. Glucose is a source of energy for body cells. The body regulates its amount in the blood with various hormones (such as insulin) and enzymes. If there is too much or too little sugar, then something is wrong with the endocrine or excretory system.

Proteins

• Albumin . It is a protein that is produced by the liver. Blood plasma is approximately 60% albumin.
• Total protein . There are several dozen different proteins in the blood. Total protein is the average total of them.
• Specific proteins . These are separate types of blood proteins, a change in the level of which may be associated with serious diseases. Specific ones include, in particular, C‑reactive protein (it signals an acute inflammatory process in the body), ferritin (needed for normal absorption of iron), myoglobin (creates the necessary supply of oxygen in muscles, including the heart), rheumatoid factor (antibodies that are produced only in case of serious diseases: infectious, muscular and connective tissues, autoimmune, oncological and others). Analysis for specific proteins is not always included in the standard LHC. If the doctor wants to find out the content of a particular substance in the blood, he will write about it in the direction for the study.

Lipids

The so-called lipid panel allows you to check the level of various types of cholesterol.

• High density lipoproteins (HDL) . This is the so-called good cholesterol, which removes harmful substances from the blood and helps the liver break them down.
• Low density lipoproteins (LDL) . We are talking about “bad” cholesterol, which causes the formation of plaques in the vessels and increases the risk of cardiovascular disease.
• Total cholesterol . The sum of the values ​​of “good” and “bad”.

Liver tests

This is the name given to the assessment of the level of certain enzymes associated with the condition of the liver.

• Total bilirubin . It is an orange-yellow pigment that is formed when hemoglobin is broken down. Bilirubin is toxic, so normally the liver quickly removes it from the body. But if hemoglobin is destroyed too actively or the liver cannot cope with normal volumes of bilirubin, the level of pigment in the blood rises sharply. This is often manifested externally – yellowing of the skin and whites of the eyes (jaundice).
• Alanine aminotransferase (AlAt, ALT) . Liver enzyme necessary for amino acid metabolism. Its level rises with liver damage.
• Aspartate aminotransferase (AsAt, AST) . Another enzyme that is released into the blood during serious disorders in the liver.
• Alkaline Phosphatase . This is an enzyme involved in phosphorus metabolism. Its increase is also a marker of liver problems.

Kidney tests

• Creatinine . This is a waste product that is formed in the muscles. It is excreted from the blood by the kidneys, so the level of creatinine is a good indicator of the work of this paired organ.
• Uric acid . Formed in the liver and again excreted from the blood by the kidneys. If they fail (or, on the contrary, are unhealthy active), the level of uric acid in the blood rises (or falls).
• Urea . It is also formed in the liver, where proteins are broken down, and excreted from the blood by the kidneys.

Inorganic substances (minerals, electrolytes) and vitamins

• Calcium . One of the most important minerals in the body. Without it, the normal functioning of muscles, nerves, and heart is impossible. In addition, it is critical for bone development and repair.
• Sodium . Responsible for the transmission of nerve impulses and helps to absorb calcium.
• Magnesium . Like sodium, it is actively involved in the transmission of nerve impulses.
• Chlorine . Helps to regulate the amount of fluid in the body and maintain acid-base balance.
• Potassium . Critical to the normal functioning of the heart.
• Iron . Necessary for the delivery of oxygen to organs and tissues.
• Phosphorus . The nervous, muscular and skeletal systems are in great need of it.
• Folic acid . Participates in a huge number of processes in the body – from the absorption of amino acids and glucose to the production of blood.
• Vitamin B12 . It is essential for the production of red blood cells – erythrocytes.

What are the norms of blood parameters in LHC

The form with the results of a biochemical blood test, as a rule, is a table of three columns. The first contains the name of the indicator, the second contains the range of its normal values, and the third contains your result.

To check the norm, first of all, be guided by the numbers indicated on the form issued to you. The fact is that laboratories conduct tests on different reagents and under different conditions. Therefore, the optimal value ranges may vary slightly depending on the organization that processed your analysis. Only one thing is important for you: to check whether the result falls within the limits of the norms established by a particular laboratory.

The figures below are indicative for the most common indicators.

902 55

Indicator	Norm for an adult
Glucose	3, 9-5.6 mmol/l
Albumin	34-54 g/l
Total protein	60–83 g/l
HDL cholesterol	40 mg/dl and above for men; 50 mg/dl and above for women
LDL cholesterol	Less than 100 mg/dL
Total cholesterol	125–200 mg/dL
Total bilirubin	1.71–20.5 µmol/l
Alat , ALT	4–36 U/L
AsAt, AST	8–33 U/L
Alkaline Phosphatase	20-140 U/L
Creatinine	74 –107 µmol/L
Uric acid	3. 5-7.2 mg/dl
Urea	2.5-7.1 mmol/l
Calcium 90 259	2.2-2.7 mmol/l

How to decode a biochemical blood test

This can and should be done only by the doctor who issued you a referral for analysis. For the reason that many different factors affect blood biochemistry.

Thus, an elevated blood glucose level can be both a symptom of prediabetes or diabetes, and a sign that you were irresponsible about the analysis and, let’s say, drank sweet coffee before it.

There are other examples. Elevated liver function tests are a marker of hepatitis and sometimes cirrhosis. But at the same time, ALT and AST can rise if you are being treated for a bacterial infection by taking antibiotics and other medications. A low urea level is a sign of serious liver damage. Or banal malnutrition if you are on a strict diet.

In general, let’s repeat it again. Only the doctor observing you should decipher the LHC.