High IgA: what it means

Lab Tests Online UK explains that IgA makes up about 15% of total lung and stomach secretions, is found in breast milk, and provides protection in mucosal areas such as the sinuses, lungs, stomach and intestines. A baby does not make significant amounts of its own IgA until after about 6 months of age. There are two subclasses, IgA1 and IgA2.

Because IgA works at the body's surfaces, it can rise when those surfaces are chronically challenged by infection, inflammation or damage, which is why a raised result is common and is usually looked at in the context of the other immunoglobulins.

The sources used here do not give a list specific to IgA alone. Lab Tests Online UK lists conditions that can cause a polyclonal increase in any or all of IgG, IgA and IgM, which therefore apply to IgA.

• Acute and chronic infections.

• Autoimmune disorders, including rheumatoid arthritis, systemic lupus erythematosus and scleroderma.

• Cirrhosis.

• Chronic inflammation and inflammatory disorders.

• Hyperimmunisation reactions and Wiskott-Aldrich syndrome.

A monoclonal increase in one class, with or without decreases in the other two, is seen in multiple myeloma, chronic lymphocytic leukaemia, MGUS and lymphoma. Lab Tests Online UK says if one immunoglobulin type is markedly raised, immunofixation can determine whether it comes from clones of an abnormal plasma cell, and that when myeloma is suspected a serum protein electrophoresis should always be carried out at the same time so that a paraprotein is not missed.

Myeloma UK describes MGUS as a non-cancerous condition that usually causes no symptoms, affects about 1 in 30 people over 50, and is monitored rather than treated. A small proportion go on to develop myeloma, so regular blood tests are used to look for change. Myeloma UK also describes related conditions where the paraprotein causes symptoms, most commonly kidney problems.

The names are similar, and people often wonder if a high IgA result means kidney disease. Kidney Care UK describes IgA nephropathy as a rare kidney condition in which IgA gets trapped in the kidney filters and causes inflammation and damage, affecting around 1 in 50,000 people in the UK. Most people have no symptoms; those who do may have blood in the urine, protein in the urine, swelling or high blood pressure.

The charity says it is often suspected after a routine urine test shows blood or protein, and that a kidney biopsy confirms the diagnosis by showing IgA deposits in the glomeruli. A blood IgA level is not described there as the way the condition is diagnosed, and a high IgA on its own does not mean someone has it. If you have blood or protein in the urine as well as an abnormal immunoglobulin result, tell your GP.

This table summarises how the sources distinguish the main explanations.

A GP will usually view the IgA result alongside IgG and IgM, a full blood count, inflammatory markers, liver and kidney function, and a urine test. If the pattern suggests a paraprotein, electrophoresis is added and a haematology opinion may follow. If a clear cause such as infection resolves, the immunoglobulins may simply be rechecked later.

Lab Tests Online UK points out that immunoglobulins mostly do not respond to lifestyle changes and that the right response is to find the cause. It is important not to stop or change medicines in response to the result without talking to the prescriber.