Inflammation and immunity · Blood

IgA (immunoglobulin A)

The amount of IgA antibodies; shows an IgA deficiency, which also matters for the celiac disease test.

At a glance

Measured in blood
In 4 test panels
No special preparation

Explanation

IgA (immunoglobulin A): what is measured?

Immunoglobulins are defense proteins (antibodies) that white blood cells make to clear bacteria, viruses and other invaders. IgA is the type that mainly works on the mucous membranes: in the nose and throat, airways, intestines, saliva and breast milk. The test measures the total amount of IgA in the blood, so not the defense against one particular pathogen. In young children, the value is lower than in adults.

What can it detect?

IgA deficiency (too little IgA), often without symptoms
A false-negative celiac disease test: the standard test uses IgA antibodies, which are missing with an IgA deficiency
A broader immune disorder, if IgG and IgM are also low
Rarely: a condition in which one group of immune cells makes too much of one type of immunoglobulin (M protein)

Result

What does the result mean?

IgA (immunoglobulin A) too high

A slightly raised IgA is common during or shortly after an infection and is then usually harmless. Long-lasting inflammation, autoimmune diseases and liver diseases can also increase the amount of immunoglobulins. The raised value itself does not cause symptoms; any symptoms belong to the cause. Rarely, a strongly raised value fits a condition in which one group of immune cells makes too much of one type of immunoglobulin (an M protein); this is investigated further with protein electrophoresis.

IgA (immunoglobulin A) too low

A low or undetectable IgA (IgA deficiency) often causes no symptoms and is sometimes discovered by chance, for example when registering as a blood donor. Other people, on the other hand, have more frequent infections of the sinuses, ears, lungs, intestines or urinary tract. With an IgA deficiency, the usual celiac disease test can wrongly come out negative, because it relies on IgA antibodies. In children under 4, a low value can be normal, because the body does not yet make IgA well at that age. Some people with IgA deficiency can become seriously ill from blood or blood products; it is important for doctors to know this.

After an abnormal result

With a low IgA, the GP usually also measures IgG and IgM and, when celiac disease is in question, IgG antibodies against transglutaminase. With repeated or severe infections, a referral follows to an internist (specialist in internal medicine), immunologist or pediatrician. A strongly raised value without a clear cause is usually investigated further with protein electrophoresis.

Reliability

How reliable is the test?

IgA can be measured accurately, but a single value says little about how well your immune system works. According to the Dutch Society for Clinical Chemistry (NVKC), total IgA is mainly measured alongside the celiac disease test, to rule out a false-negative result due to IgA deficiency; IgA deficiency is defined as a value below 0.07 g/l. With frequently recurring infections, IgA is assessed together with IgG and IgM. The cause of a value that is too high only becomes clear with further tests.

What can affect the result?

Reference values depend on age and differ by laboratory.
A recent or ongoing infection or inflammation can temporarily raise the value.
Some medicines can reduce the production of IgA.
The result says nothing about the defense against a specific pathogen.

Who it is for

Who is the test useful for?

Useful for

Useful with frequently recurring infections of the airways, ears, sinuses or intestines, and as an addition to testing for celiac disease to rule out a false-negative result. In young children, a low value is often normal. For people without symptoms, the test yields little: an IgA deficiency found by chance usually causes no symptoms and is not treated.

How common is it?

About 1 in 700 people has an IgA deficiency, usually without symptoms. IgA deficiency is more common in people with celiac disease. How often a slightly raised IgA due to an infection or inflammation is found has not been recorded in Dutch figures.

NVKC Zinnige Diagnostiek (celiac disease)

Drawbacks and risks

A low or slightly raised IgA found by chance without symptoms can cause unnecessary worry and follow-up tests.
A normal value does not mean that the immune system works well against all infections.

Get tested

IgA (immunoglobulin A): test panels

IgA (immunoglobulin A) is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.

Blood draw
Immunoglobulin: IgA, IgG, and IgM
Total IgA, IgG, and IgM; broad immunity assessment.
€ 68,00
Blood draw
Celiac Disease: IgA/IgG Transglutaminase
IgA and IgG against transglutaminase; for celiac disease screening.
€ 78,00
Blood draw
Immunoglobulin A (IgA)
Total IgA in blood; an antibody class of the immune system.
€ 26,95
Fingerstick
Immunoglobulin A (IgA) (finger-prick)
Total IgA in blood; an antibody class of the immune system.
€ 26,95

How reliable is the test?

IgA (immunoglobulin A)