Inflammation and immunity
IgA
The amount of IgA antibodies; shows an IgA deficiency, which also matters for the celiac disease test.
Everything about this testWhat it measures
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.
- 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)
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.
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.
If your result is abnormal
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
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.
Limitations
- 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.
How common is this
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.
Who is this 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.
Downsides 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.
Sources
Always discuss an abnormal result with your GP. If a result is strongly abnormal, we try to reach you as soon as possible. Read your result yourself as well and contact your GP if in doubt. A test does not make a diagnosis. Read more about risks and results