Blood Test: Immunoglobulins (IgA, IgG, IgM) (for Parents)

en español: Análisis de sangre: Inmunoglobulinas (IgA, IgG, IgM)

Medically reviewed by: Larissa Hirsch, MD

What Is a Blood Test?

A blood test is when a blood sample is tested in a lab. Doctors order blood tests to check things such as the levels of glucose, hemoglobin, or white blood cells. This can help them find problems like a disease or medical condition. Sometimes, blood tests can help them see how well an organ (such as the liver or kidneys) is working.

What Is an Immunoglobulin Test?

An immunoglobulin (im-yeh-no-GLOB-yeh-len) test measures the level of types of antibodies in the blood. The immune system makes antibodies to protect the body from bacteria, viruses, and allergens.

The body makes different antibodies, or immunoglobulins, to fight different things. For example, the antibody for chickenpox isn’t the same as the antibody for mononucleosis. Sometimes, the body may even mistakenly make antibodies against itself, treating healthy organs and tissues like foreign invaders. This is called an autoimmune disease.

The types of antibodies are:

• Immunoglobulin A (IgA): It’s found in the linings of the respiratory tract and digestive system, as well as in saliva (spit), tears, and breast milk.
• Immunoglobulin G (IgG): This is the most common antibody. It’s in blood and other body fluids, and protects against bacterial and viral infections. IgG can take time to form after an infection or immunization.
• Immunoglobulin M (IgM): Found mainly in blood and lymph fluid, this is the first antibody the body makes when it fights a new infection.
• Immunoglobulin E (IgE): Normally found in small amounts in the blood. There may be higher amounts when the body overreacts to allergens or is fighting an infection from a parasite.
• Immunoglobulin D (IgD): This is the least understood antibody, with only small amounts in the blood.

Why Are Immunoglobulin Tests Done?

Doctors may check immunoglobulin levels to see if a person has an infection or is protected from getting an infection (is immune to it). Doctors also use immunoglobulin tests to help diagnose immunodeficiencies (when the immune system isn’t working as it should). Doctors may suspect an immunodeficiency in a child who gets a lot of infections or unusual infections.

The tests might be done as part of an evaluation for allergies or autoimmune conditions such as juvenile idiopathic arthritis, lupus, and celiac disease.

How Should We Prepare for an Immunoglobulin Test?

Kids can eat and drink normally unless also getting other tests that require fasting beforehand. Tell your doctor about any medicines your child takes because some drugs might affect the test results.

Wearing a T-shirt or short-sleeved shirt for the test can make things easier for your child, and you also can bring along a toy or book as a distraction.

How Is an Immunoglobulin Test Done?

Most blood tests take a small amount of blood from a vein. To do that, a health professional will:

• Clean the skin.
• Put an elastic band (tourniquet) above the area to get the veins to swell with blood.
• Insert a needle into a vein (usually in the arm inside of the elbow or on the back of the hand).
• Pull the blood sample into a vial or syringe.
• Take off the elastic band and remove the needle from the vein.

Sometimes immunoglobulin tests can be done with a “fingerstick” test. The health professional will clean your child’s finger, then prick the tip of it with a tiny needle (or lancet) to collect the blood.

In babies, blood draws are sometimes done as a “heel stick collection.” After cleaning the area, the health professional will prick your baby’s heel with a tiny needle (or lancet) to collect a small sample of blood.

Collecting a sample of blood is only temporarily uncomfortable and can feel like a quick pinprick.

Can I Stay With My Child During an Immunoglobulin Test?

Parents usually can stay with their child during a blood test. Encourage your child to relax and stay still because tensing muscles can make it harder to draw blood. Your child might want to look away when the needle is inserted and the blood is collected. Help your child to relax by taking slow deep breaths or singing a favorite song.

How Long Does an Immunoglobulin Test Take?

Most blood tests take just a few minutes. Sometimes, it can be hard to find a vein, so the health professional may need to try more than once.

What Happens After an Immunoglobulin Test?

The health professional will remove the elastic band and the needle and cover the area with cotton or a bandage to stop the bleeding. Afterward, there may be some mild bruising, which should go away in a few days.

When Are Immunoglobulin Test Results Ready?

It may take a few days for the results to be available. If the test results show signs of a problem, the doctor might order other tests to figure out what the problem is and how to treat it.

Are There Any Risks From Immunoglobulin Tests?

An immunoglobulin test is a safe procedure with minimal risks. Some kids might feel faint or lightheaded from the test. A few kids and teens have a strong fear of needles. If your child is anxious, talk with the doctor before the test about ways to make it easier. 

A small bruise or mild soreness around the blood test site is common and can last for a few days. Get medical care for your child if the discomfort gets worse or lasts longer.

If you have questions about the immunoglobulin test, speak with your doctor or the health professional doing the blood draw.

Medically reviewed by: Larissa Hirsch, MD

Date reviewed: April 2020

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High vs Low vs Normal Levels of (Ig) Antibodies

Written by WebMD Editorial Contributors

• Types of Immunoglobulin
• Why You Might Need This Test
• How the Test is Done
• What Do My Results Mean?

This test checks the amount of certain antibodies called immunoglobulins in your body.

Antibodies are proteins that your immune cells make to fight off bacteria, viruses, and other harmful invaders. The immunoglobulin test can show whether there’s a problem with your immune system.

Some conditions cause your body to make too many or too few immunoglobulins.

Having too few immunoglobulins in your blood gives you a greater chance of getting infections. Having too many could mean you have allergies or an overactive immune system.

Your body makes a few different types of immunoglobulin antibodies, including these:

Immunoglobulin A: IgA antibodies are found in the mucous membranes of the lungs, sinuses, stomach, and intestines. They’re also in fluids these membranes produce, like saliva and tears, as well as in the blood.

Immunoglobulin G: IgG is the most common type of antibody in your blood and other body fluids. These antibodies protect you against infection by “remembering” which germs you’ve been exposed to before.

If those germs come back, your immune system knows to attack them. Your doctor can test for IgG to figure out whether you’ve been infected by certain kinds of bacteria or virus.

Immunoglobulin M: Your body makes IgM antibodies when you are first infected with new bacteria or other germs.

They are your body’s first line of defense against infections. When your body senses an invader, your IgM level will rise for a short time. It will then begin to drop as your IgG level kicks in and increases to protect you long-term.

Immunoglobulin E: Your body makes IgE antibodies when it overreacts to substances that aren’t harmful, such as pollen or pet dander. Your doctor will likely measure your IgE levels if you have a blood test to check for allergies.

Your doctor might order an immunoglobulin test if you get a lot of infections — especially infections of the sinuses, lungs, stomach, or intestines.

They may also order the test if you have:

• Diarrhea that doesn’t go away
• Unexplained weight loss
• Fevers that can’t be explained by another cause
• Skin rashes
• Allergies
• Sickness after traveling
• HIV/AIDS or multiple myeloma (a type of cancer), or another condition that needs to be monitored

Doctors often measure IgA, IgG, and IgM together to get a snapshot of your immune function. A lab tech will usually take a sample of your blood by inserting a needle into a vein in your arm. The blood collects into a tube or vial.

Another way to do this test is with a sample of what’s called cerebrospinal fluid (CSF).

CSF surrounds your brain and spinal cord. The doctor will take a sample of this fluid with a lumbar puncture (often called a “spinal tap”).

For this, you go to an outpatient facility or a hospital. A technician will give you a shot in your back to help numb any pain.

You will likely lie on your side with your knees pulled up to your chest, or you sit on a table. The technician inserts a hollow needle between two vertebrae in your lower spine and removes a small amount of fluid so it can be tested.

The sample will be sent to a lab for testing. This might take a few days.

Depending on your results, the doctor might need to do other tests, such as a:

• Complete blood count (CBC)
• Protein blood test
• Urine test to check for kidney problems

If your immunoglobulin level is high, it might be caused by:

• Allergies
• Chronic infections
• An autoimmune disorder that makes your immune system overreact, such as rheumatoid arthritis, lupus, or celiac disease
• Liver disease
• Inflammatory bowel disease
• Cancer, such as multiple myeloma, lymphoma, or leukemia

Low levels of immunoglobulins mean your immune system isn’t working as well as it should. This can be caused by:

• Medicines that weaken your immune system, such as steroids
• Diabetes complications
• Kidney disease or kidney failure
• A weakened immune system that you were born with or developed (as with HIV/AIDS)

Just because your immunoglobulin level is high or low doesn’t mean you have one of these conditions.

Each person’s test can differ based on the method the lab uses to check the results. Talk to your doctor about your test results, and find out what you should do next.

Top Picks

Take a blood test for class G immunoglobulins (IgG)

Method of determination
Immunoturbidimetry.

Test material
Blood serum

Home visit available

Online check-in

Synonyms: Class G antibodies; IgG is common.

Immunoglobulin G; IgG total, serum.

Immunoglobulin class G (IgG) study summary

Class G immunoglobulins make up about 75-80% of all immunoglobulins and 10-20% of total serum protein concentration. Synthesized by B-lymphocytes.

The molecule consists of two heavy and two light chains. The half-life of their elimination from the blood is 23-25 ​​days. About half of the total amount of IgG in the body is in the vascular bed. Approximately 1/4 of the serum IgG daily diffuses through the capillaries into the interstitium and approximately the same amount returns to the bloodstream from the lymphatic vessels. Immunoglobulins of this class have a small molecular weight and therefore penetrate (the only of all immunoglobulins) through the placenta from mother to fetus, providing passive immunity of the newborn to certain infectious diseases. In the blood of the fetus and the newborn, maternal IgG predominates.

IgG play a major role in providing long-term humoral immunity in infectious diseases. These are the main antibodies of the human secondary immune response to most foreign antigens. Activated antigen-specific B cells during the development of the immune response are able to switch from the production of class M immunoglobulins to the production of immunoglobulins of other classes (IgG, IgA), which is the mechanism for changing the isotype of antibodies in response to exposure to antigens and the basis of the secondary immune response. In this case, there is an increase in the avidity (affinity) of antibodies to the antigen that stimulated their production.

Under what conditions does the level of class G immunoglobulins change

The synthesis of class G immunoglobulins and their concentration in blood serum increase in chronic or recurrent infections and autoimmune diseases. IgGs are involved in the neutralization of bacterial toxins, they are able to bind complement, can act as opsonins, are involved in the stimulation of phagocytosis and in antibody-dependent cell-mediated cytotoxicity. Deficiency of IgG weakens resistance to infections.

Many of the clinically significant autoantibodies found in autoimmune diseases belong to this class of immunoglobulins.

IgG is the most common type of paraprotein found in multiple myeloma (electrophoresis with immunofixation is used to confirm the monoclonal nature of IgG – see tests nos. 4050, 4051.

IgG M-protein level above 40 g/l may be accompanied by hyperviscosity syndrome.

What is the purpose of class G immunoglobulins (IgG) determination in blood serum

For recurrent (non-acute) infectious diseases, immunodeficiency conditions, autoimmune pathologies, blood diseases and neoplasms.

Detection of IgG antibodies to the S protein of the coronavirus SARS-CoV-2 (COVID-19)

Code: 09.1928

Price: 850 rubles

Description

Semi quantitative assessment of IgG class antibodies to the spike (S) protein of the pathogen of the new coronavirus infection allows us to judge the presence of post-vaccination immunity to COVID-19. You can track the dynamics of antibody levels and assess how the resistance of the immune response to COVID-19 changes over time. Sputnik V is a two-component vaccine against COVID-19 containing the gene for the S-protein of the coronavirus against which antibodies are produced. It is advisable to evaluate post-vaccination immunity no earlier than 21 days after the introduction of the second component of the vaccine.

General information about the test

This test allows you to determine the concentration in the blood of IgG antibodies to the spike (S) protein of the coronavirus COVID-19.

Coronavirus consists of 4 structural proteins: S-protein (spike), N-protein, or nucleocapsid protein, M – membrane protein and E – shell protein. On the surface of the coronavirus are protrusions that resemble spikes or a crown, which gave the name to this group of viruses. The protrusions are protein molecules of protein S, with their help the virus enters the cell.

From the moment the virus enters the body, immunoglobulins, or antibodies, begin to be produced that recognize and bind foreign antigens. IgM antibodies are the first to be produced, they serve as a marker of the early stage of the disease or the acute period. IgG antibodies are gradually produced after 2-3 weeks from the onset of the disease and circulate in the bloodstream. After an infection, IgG antibodies to the nucleocapsid protein (N) are formed. Antibodies to the S-protein are formed both after an illness and after vaccination.

“Sputnik V” is a Russian-made two-vector vaccine against a new coronavirus infection COVID-19. A vector is a virus that is unable to reproduce in the human body and does not cause disease; it is used to transport the genetic material of the coronavirus into the cell. The vector with the gene encoding the spike protein of the coronavirus enters the cells, which triggers the production of the S-protein. In response, immune cells begin to synthesize IgG antibodies to the spike protein antigen. If the body encounters the COVID-19 coronavirus in the future, then the blood of a vaccinated person will already contain antibodies, thus providing immunity against the coronavirus COVID-19. After vaccination with Sputnik V, the immune response is formed after two intramuscular applications with an interval of 21 days.

Quantitative study allows not only to assess the presence or absence of antibodies to the SARS-CoV-2 S-protein, but also to determine their level, which makes it possible to assess the strength of immunity and the dynamics of antibody growth.

Preparation

• Do not eat for 2-3 hours before the examination, you can drink pure non-carbonated water.
• Do not smoke for 30 minutes before the test.

Indications

• After vaccination against COVID-19 with the Sputnik V vaccine.
• After experiencing COVID-19.

Interpretation of results

Reference values ​​

Negative result: 0 – 12 IU/ml.

If no IgG antibodies to coronavirus are detected in the blood, there is no immunity to the virus. The reason may be:

• lack of contact with coronavirus infection;
• period of early infection;
• insufficient period after infection or vaccination, during which antibodies did not have time to develop;
• no immune response to vaccination.