IgA

Most UK laboratories print 0.8 to 4.0 g/L for adults; some print 0.7 to 4.0. Ranges are lower in children. About 1 in 600 people in the general population make very little IgA from birth, most without any ill effect.

IgA is the antibody that guards the surfaces of the body, the lining of the gut, the airways and the mouth, and is found in saliva, tears and breast milk as well as in the blood. The blood test measures the total amount of IgA of all specificities. It is usually reported together with IgG and IgM.

Doctors request it with IgG and IgM when looking at recurrent infections, unexplained high blood protein and myeloma. It is also measured alongside the coeliac antibody test, because that test relies on IgA and gives a false negative in people who make very little of it.

• Liver disease, particularly alcohol-related
• Long-term infections and inflammatory conditions, including inflammatory bowel disease
• Myeloma of the IgA type
• Some autoimmune conditions, including IgA nephropathy and IgA vasculitis
• HIV infection, in the general population

• Selective IgA deficiency, an inherited trait in about 1 in 600 people, usually harmless
• Immune-suppressing medicines and chemotherapy
• Protein loss through the kidneys or the gut
• Some epilepsy medicines
• Inherited immune deficiencies

• A low IgA is a common inherited trait that most people never know they have
• It is lower in children and takes until the teens to reach adult levels
• Methods differ between laboratories

No fasting needed. Read alongside IgG, IgM and, where relevant, the coeliac antibody test on the same sample.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.