Immunoglobulin A (IgA)
Other marker
IgA
Immunoglobulin A (IgA)
The main antibody class guarding mucosal surfaces (gut, respiratory, and urogenital tracts) and also present in serum. Total serum IgA is measured to assess humoral immune status and, importantly, to check for selective IgA deficiency before interpreting IgA-based coeliac antibody tests.
PED Notes
The most practical reason this shows up alongside athlete panels is coeliac testing. The standard coeliac screen (tissue transglutaminase IgA and endomysial IgA) relies on the person making normal amounts of IgA; selective IgA deficiency, which affects roughly 1 in 500 people, produces falsely negative coeliac antibodies. So a total IgA is often drawn with those tests. IgA can also rise with chronic mucosal inflammation, liver disease, and infections.
When high
When high (>400 mg/dL):
- Polyclonal elevations are common and usually reactive: chronic infections, chronic liver disease (especially alcohol-related), inflammatory bowel or mucosal disease, and some autoimmune conditions
- A markedly raised IgA with other abnormalities can rarely reflect a monoclonal (paraprotein) process and warrants protein electrophoresis if suspected
- Action: interpret alongside the clinical picture, liver markers, and inflammatory markers; an isolated mild elevation is often benign and non-specific
When low
When low (<70 mg/dL) or undetectable:
- Selective IgA deficiency is the key finding: it is usually asymptomatic but has two practical consequences. First, IgA-based coeliac tests (tTG-IgA, endomysial IgA) can be falsely negative, so coeliac disease must be screened with IgG-based tests (deamidated gliadin IgG) instead. Second, IgA-deficient individuals have a small risk of reactions to blood products containing IgA
- Some people with low IgA have more frequent respiratory or gut infections; recurrent or severe infections warrant immunology referral to exclude a broader immunodeficiency (for example common variable immunodeficiency)
- There is no supplement that raises IgA; management is about correct test interpretation and, where needed, specialist assessment
History Chart
Reading History
Frequently Asked Questions
Reference Ranges
Standard Range