IgA (immunoglobulin A)

Being tested for coeliac disease? Total IgA is almost always measured alongside antibody testing because people with too little IgA may have a false-negative coeliac test. IgA testing also helps with frequent respiratory or intestinal infections; doctors use it in certain inflammatory and autoimmune diseases too.

Who is this test for

• people being tested for coeliac disease, alongside transglutaminase IgA;
• people with frequent sinus, ear, bronchial or lung infections, or frequent intestinal infections and diarrhoea;
• when a doctor suspects weakened immunity, together with IgG and IgMtests;
• people whose close relatives have IgA deficiency;
• people with autoimmune or chronic liver disease, at a doctor’s discretion;
• when total blood proteins are high or protein electrophoresis shows an abnormality.

What the test reveals

Immunoglobulin A accounts for 10 to 15 % of blood antibodies but performs its most important work outside blood. It is found in tears, saliva, sweat, breast milk and respiratory and intestinal mucus, protecting mucosal surfaces against viruses and bacteria. IgA does not cross the placenta, so children produce it themselves and reach adult levels only in adolescence.

The test measures total blood IgA. The most common disorder it detects is isolated (selective) IgA deficiency. It occurs in approximately one in several hundred people, and most affected people have no symptoms. It is more common in people with coeliac disease than others.

The test and preparation

The sample is venous blood, and collection takes a few minutes. Fasting is not required for IgA. If coeliac tests are also performed, do not remove gluten before testing: these tests are reliable only if you eat it regularly, ideally for at least six weeks in several meals each day. Also state which medicines you take.

What your results mean

The reference interval depends on age and method and is printed on the report. In adults it is usually approximately 0,7 to 4 g/L; children have lower values. A doctor interprets the result alongside symptoms and other findings.

• Very low or undetectable IgA in people over four years old, with normal IgG and IgM, suggests selective IgA deficiency. Transglutaminase IgA is then unreliable, so a doctor uses IgG-class coeliac tests, for example transglutaminase IgG.
• Mildly low IgA is often normal for age in young children. Some medicines, such as certain epilepsy drugs, can also lower it in adults; a doctor assesses whether the test should be repeated.
• High IgA may accompany chronic infections, liver disease, autoimmune diseases and certain kidney diseases. Rarely, it indicates a blood disease, checked through protein electrophoresis.
• Normal IgA means that an IgA-class coeliac test is reliable, provided you have been eating gluten.

How to arrange testing

You can come for blood collection without an appointment or referral at one of our branches throughout Croatia (listed on the Contactpage). Prices for all tests and panels are listed in the price list. If you are being tested for coeliac disease, the Coeliac Panel combines total IgA, transglutaminase IgA and IgG, and faecal calprotectin.

Frequently asked questions

Why is total IgA tested alongside a coeliac test?

People without enough IgA cannot produce IgA-class coeliac antibodies either. The test may then be negative despite disease, so total IgA shows whether the result can be trusted.

Is IgA deficiency dangerous?

Most people with IgA deficiency have no symptoms and need no special treatment. Some have more frequent infections, allergies or autoimmune diseases. Before receiving blood or blood products, tell your doctor about IgA deficiency because reactions can rarely occur.

What if I already avoid gluten?

Total IgA is unaffected, but coeliac tests may be falsely negative. Before testing, agree with your doctor whether and for how long gluten should be reintroduced.

Can IgA levels change over time?

In children, IgA rises with age, so a low result in early childhood is often repeated later. In adults, marked IgA deficiency is usually permanent, while milder abnormalities can be temporary, for example due to medicines.