Faced with a blood test, some terms can seem complex. This is often the case for Immunoglobulin A (IgA). However, understanding this marker is an important step to better grasp your health status, particularly your immune system. This guide aims to clarify what IgA is, why it is measured, and how to interpret the results with your doctor.

The goal is to provide you with reliable and accessible information to empower you as an informed participant in your medical follow-up.

What is Immunoglobulin A (IgA)?

Immunoglobulin A (IgA) is a type of antibody. Antibodies are proteins produced by our immune system to recognize and neutralize foreign agents such as viruses and bacteria. IgA plays an absolutely essential role as a first line of defense.

It is primarily found in the mucous membranes. These tissues line the inside of organs that are in contact with the outside. IgA is therefore present in:

• The digestive tract (intestine, stomach).
• The respiratory tract (nose, bronchi, lungs).
• Secretions like saliva, tears, and breast milk.

Thanks to this strategic location, IgA prevents microbes from entering our body. It acts as a protective barrier on the most exposed surfaces. A small part of IgA also circulates in the blood (serum IgA), and it is this fraction that is measured during a blood test.

Why Measure Immunoglobulin A (IgA) Levels?

A doctor may order an Immunoglobulin A (IgA) test for several reasons. This analysis helps explore different clinical situations.

The most common reasons include:

• Investigating recurrent infections, particularly of the sinuses, lungs, or digestive tract, which could suggest a weakness in the immune system.
• Exploring a possible autoimmune disease, as abnormal IgA levels can be associated with conditions like celiac disease or lupus.
• Diagnosing or monitoring certain specific diseases, such as IgA nephropathy or a monoclonal gammopathy.

IgA levels are often measured at the same time as other immunoglobulins (IgG and IgM) to get an overview of the immune response.

Interpreting IgA Test Results

Reference values for IgA vary greatly depending on age. An infant has a very low level that gradually increases during childhood to reach adult values. It is therefore crucial to compare the result to the laboratory’s norms, specific to the age group. An isolated result has little meaning without clinical context.

Elevated Immunoglobulin A (IgA) Levels: What are the Causes?

An increase in IgA levels is called IgA hypergammaglobulinemia. The doctor must first determine if this increase is polyclonal or monoclonal.

Polyclonal Increase

This means that many clones of immune cells are producing excess IgA, often in response to stimulation. This is the most frequent case.

• Possible causes: chronic mucosal infections, chronic inflammatory diseases (rheumatoid arthritis, lupus), liver diseases (cirrhosis).

Monoclonal Increase

Here, a single clone of cells produces a large amount of a single type of IgA. This is a situation that requires further investigation.

• Main cause: IgA multiple myeloma, a form of bone marrow cancer. Other tests are needed to confirm this diagnosis.

Low Immunoglobulin A (IgA) Levels: What Does This Mean?

A low level can indicate an IgA deficiency. The most common is selective IgA deficiency. It is the most frequent primary immunodeficiency in the general population.

Many people with selective IgA deficiency are perfectly healthy and show no symptoms. For others, this deficiency can manifest as:

• Recurrent ENT and respiratory infections.
• Gastrointestinal infections.
• An increased risk of allergies and autoimmune diseases, such as celiac disease.

Pathologies Specifically Linked to IgA

Certain diseases are directly associated with a dysfunction of immunoglobulin A.

IgA Nephropathy (Berger’s Disease)

This is the most common glomerular disease (affecting the kidney filters) worldwide. It is caused by deposits of immunoglobulin A in the kidneys, which creates inflammation and can impair kidney function over the long term.

Celiac Disease

Gluten intolerance is strongly associated with IgA. Diagnosis relies heavily on the detection of IgA autoantibodies directed against components of the intestine, such as anti-tissue transglutaminase IgA. In a person with IgA deficiency, this test may be falsely negative. The doctor must then look for other markers.

Frequently Asked Questions About Immunoglobulin A (IgA)

Do I Need to Fast for an IgA Test?

No, it is generally not necessary to fast for this blood test. Food does not have a direct impact on the result.

What is the Difference Between IgA, IgG, and IgM?

These are three classes of antibodies with different roles. IgM is the first to respond during a new infection. IgG is the most abundant in the blood and provides long-term immune memory. IgA, on the other hand, specializes in protecting the mucous membranes.

Does IgA Deficiency Pose a Risk for Transfusions?

Yes, potentially. A person with selective IgA deficiency may develop antibodies against IgA present in transfused blood products (blood, plasma). This can cause a severe transfusion reaction. It is therefore vital that individuals with a known deficiency inform their doctor and carry an alert card.

Conclusion: IgA, A Guardian of Our Mucous Membranes

Immunoglobulin A (IgA) is a key player in our immune system. The measurement of this antibody provides valuable information for the diagnosis and monitoring of many conditions, ranging from recurrent infections to autoimmune and kidney diseases.

It is essential to remember that the interpretation of an IgA level, whether high or low, always depends on the overall clinical context. This result is one piece of the puzzle that only your doctor can assemble correctly. By understanding its role, you are better equipped to communicate with healthcare professionals and participate in your care journey.

Additional resources

• To deepen your knowledge of this blood marker, click here.
• To extend your knowledge and decipher other markers, more articles are available here.

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